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4785 commits
| Author | SHA1 | Message | Date | |
|---|---|---|---|---|
Linus Torvalds
|
cec1e6e5d1 |
sched_ext: Fixes for v6.17-rc7
This contains a fix for sched_ext idle CPU selection that likely fixes a substantial performance regression. The scx_bpf_select_cpu_dfl/and() kfuncs were incorrectly detecting all tasks as migration-disabled when called outside ops.select_cpu(), causing them to always return -EBUSY instead of finding idle CPUs. The fix properly distinguishes between genuinely migration-disabled tasks vs. the current task whose migration is temporarily disabled by BPF execution. -----BEGIN PGP SIGNATURE----- iIQEABYKACwWIQTfIjM1kS57o3GsC/uxYfJx3gVYGQUCaNF8hQ4cdGpAa2VybmVs Lm9yZwAKCRCxYfJx3gVYGYhsAPwNeMGqniyewfciL6q+9Yjnxudn+bCzntvTidY/ EbV3vgD9GPily3kjKhuPBGIq5hnyiV1DsmmCTIu8vaj7RB4uYw8= =k2RU -----END PGP SIGNATURE----- Merge tag 'sched_ext-for-6.17-rc7-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext Pull sched_ext fix from jun Heo: "This contains a fix for sched_ext idle CPU selection that likely fixes a substantial performance regression. The scx_bpf_select_cpu_dfl/and() kfuncs were incorrectly detecting all tasks as migration-disabled when called outside ops.select_cpu(), causing them to always return -EBUSY instead of finding idle CPUs. The fix properly distinguishes between genuinely migration-disabled tasks vs. the current task whose migration is temporarily disabled by BPF execution" * tag 'sched_ext-for-6.17-rc7-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext: sched_ext: idle: Handle migration-disabled tasks in BPF code |
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|
Andrea Righi
|
55ed11b181 |
sched_ext: idle: Handle migration-disabled tasks in BPF code
When scx_bpf_select_cpu_dfl()/and() kfuncs are invoked outside of
ops.select_cpu() we can't rely on @p->migration_disabled to determine if
migration is disabled for the task @p.
In fact, migration is always disabled for the current task while running
BPF code: __bpf_prog_enter() disables migration and __bpf_prog_exit()
re-enables it.
To handle this, when @p->migration_disabled == 1, check whether @p is
the current task. If so, migration was not disabled before entering the
callback, otherwise migration was disabled.
This ensures correct idle CPU selection in all cases. The behavior of
ops.select_cpu() remains unchanged, because this callback is never
invoked for the current task and migration-disabled tasks are always
excluded.
Example: without this change scx_bpf_select_cpu_and() called from
ops.enqueue() always returns -EBUSY; with this change applied, it
correctly returns idle CPUs.
Fixes:
|
||
|
Linus Torvalds
|
37889ceadd |
sched_ext: Fixes for v6.17-rc6
This contains 2 sched_ext fixes. - Fix build failure when !FAIR_GROUP_SCHED && EXT_GROUP_SCHED. - Revert "sched_ext: Skip per-CPU tasks in scx_bpf_reenqueue_local()" which was causing issues with per-CPU task scheduling and reenqueuing behavior. -----BEGIN PGP SIGNATURE----- iIQEABYKACwWIQTfIjM1kS57o3GsC/uxYfJx3gVYGQUCaMsN6g4cdGpAa2VybmVs Lm9yZwAKCRCxYfJx3gVYGRHQAP4kRGIyxCaCnoSHHDyI8R2SLUzDKvvByaVNdbKO 5VlCaAEAy0wKViyJDojpd5DXMFlFYCm8gXWQ0aD++hhYX1XfawI= =b+ar -----END PGP SIGNATURE----- Merge tag 'sched_ext-for-6.17-rc6-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext Pull sched_ext fixes from Tejun Heo: - Fix build failure when !FAIR_GROUP_SCHED && EXT_GROUP_SCHED - Revert "sched_ext: Skip per-CPU tasks in scx_bpf_reenqueue_local()" which was causing issues with per-CPU task scheduling and reenqueuing behavior * tag 'sched_ext-for-6.17-rc6-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext: sched_ext, sched/core: Fix build failure when !FAIR_GROUP_SCHED && EXT_GROUP_SCHED Revert "sched_ext: Skip per-CPU tasks in scx_bpf_reenqueue_local()" |
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Tejun Heo
|
a1eab4d813 |
sched_ext, sched/core: Fix build failure when !FAIR_GROUP_SCHED && EXT_GROUP_SCHED
While collecting SCX related fields in struct task_group into struct scx_task_group, |
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Andrea Righi
|
0b47b6c354 |
Revert "sched_ext: Skip per-CPU tasks in scx_bpf_reenqueue_local()"
scx_bpf_reenqueue_local() can be called from ops.cpu_release() when a
CPU is taken by a higher scheduling class to give tasks queued to the
CPU's local DSQ a chance to be migrated somewhere else, instead of
waiting indefinitely for that CPU to become available again.
In doing so, we decided to skip migration-disabled tasks, under the
assumption that they cannot be migrated anyway.
However, when a higher scheduling class preempts a CPU, the running task
is always inserted at the head of the local DSQ as a migration-disabled
task. This means it is always skipped by scx_bpf_reenqueue_local(), and
ends up being confined to the same CPU even if that CPU is heavily
contended by other higher scheduling class tasks.
As an example, let's consider the following scenario:
$ schedtool -a 0,1, -e yes > /dev/null
$ sudo schedtool -F -p 99 -a 0, -e \
stress-ng -c 1 --cpu-load 99 --cpu-load-slice 1000
The first task (SCHED_EXT) can run on CPU0 or CPU1. The second task
(SCHED_FIFO) is pinned to CPU0 and consumes ~99% of it. If the SCHED_EXT
task initially runs on CPU0, it will remain there because it always sees
CPU0 as "idle" in the short gaps left by the RT task, resulting in ~1%
utilization while CPU1 stays idle:
0[||||||||||||||||||||||100.0%] 8[ 0.0%]
1[ 0.0%] 9[ 0.0%]
2[ 0.0%] 10[ 0.0%]
3[ 0.0%] 11[ 0.0%]
4[ 0.0%] 12[ 0.0%]
5[ 0.0%] 13[ 0.0%]
6[ 0.0%] 14[ 0.0%]
7[ 0.0%] 15[ 0.0%]
PID USER PRI NI S CPU CPU%▽MEM% TIME+ Command
1067 root RT 0 R 0 99.0 0.2 0:31.16 stress-ng-cpu [run]
975 arighi 20 0 R 0 1.0 0.0 0:26.32 yes
By allowing scx_bpf_reenqueue_local() to re-enqueue migration-disabled
tasks, the scheduler can choose to migrate them to other CPUs (CPU1 in
this case) via ops.enqueue(), leading to better CPU utilization:
0[||||||||||||||||||||||100.0%] 8[ 0.0%]
1[||||||||||||||||||||||100.0%] 9[ 0.0%]
2[ 0.0%] 10[ 0.0%]
3[ 0.0%] 11[ 0.0%]
4[ 0.0%] 12[ 0.0%]
5[ 0.0%] 13[ 0.0%]
6[ 0.0%] 14[ 0.0%]
7[ 0.0%] 15[ 0.0%]
PID USER PRI NI S CPU CPU%▽MEM% TIME+ Command
577 root RT 0 R 0 100.0 0.2 0:23.17 stress-ng-cpu [run]
555 arighi 20 0 R 1 100.0 0.0 0:28.67 yes
It's debatable whether per-CPU tasks should be re-enqueued as well, but
doing so is probably safer: the scheduler can recognize re-enqueued
tasks through the %SCX_ENQ_REENQ flag, reassess their placement, and
either put them back at the head of the local DSQ or let another task
attempt to take the CPU.
This also prevents giving per-CPU tasks an implicit priority boost,
which would otherwise make them more likely to reclaim CPUs preempted by
higher scheduling classes.
Fixes:
|
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Christian Loehle
|
5ebf512f33 |
sched: Fix sched_numa_find_nth_cpu() if mask offline
sched_numa_find_nth_cpu() uses a bsearch to look for the 'closest'
CPU in sched_domains_numa_masks and given cpus mask. However they
might not intersect if all CPUs in the cpus mask are offline. bsearch
will return NULL in that case, bail out instead of dereferencing a
bogus pointer.
The previous behaviour lead to this bug when using maxcpus=4 on an
rk3399 (LLLLbb) (i.e. booting with all big CPUs offline):
[ 1.422922] Unable to handle kernel paging request at virtual address ffffff8000000000
[ 1.423635] Mem abort info:
[ 1.423889] ESR = 0x0000000096000006
[ 1.424227] EC = 0x25: DABT (current EL), IL = 32 bits
[ 1.424715] SET = 0, FnV = 0
[ 1.424995] EA = 0, S1PTW = 0
[ 1.425279] FSC = 0x06: level 2 translation fault
[ 1.425735] Data abort info:
[ 1.425998] ISV = 0, ISS = 0x00000006, ISS2 = 0x00000000
[ 1.426499] CM = 0, WnR = 0, TnD = 0, TagAccess = 0
[ 1.426952] GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0
[ 1.427428] swapper pgtable: 4k pages, 39-bit VAs, pgdp=0000000004a9f000
[ 1.428038] [ffffff8000000000] pgd=18000000f7fff403, p4d=18000000f7fff403, pud=18000000f7fff403, pmd=0000000000000000
[ 1.429014] Internal error: Oops: 0000000096000006 [#1] SMP
[ 1.429525] Modules linked in:
[ 1.429813] CPU: 3 UID: 0 PID: 1 Comm: swapper/0 Not tainted 6.17.0-rc4-dirty #343 PREEMPT
[ 1.430559] Hardware name: Pine64 RockPro64 v2.1 (DT)
[ 1.431012] pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
[ 1.431634] pc : sched_numa_find_nth_cpu+0x2a0/0x488
[ 1.432094] lr : sched_numa_find_nth_cpu+0x284/0x488
[ 1.432543] sp : ffffffc084e1b960
[ 1.432843] x29: ffffffc084e1b960 x28: ffffff80078a8800 x27: ffffffc0846eb1d0
[ 1.433495] x26: 0000000000000000 x25: 0000000000000000 x24: 0000000000000000
[ 1.434144] x23: 0000000000000000 x22: fffffffffff7f093 x21: ffffffc081de6378
[ 1.434792] x20: 0000000000000000 x19: 0000000ffff7f093 x18: 00000000ffffffff
[ 1.435441] x17: 3030303866666666 x16: 66663d736b73616d x15: ffffffc104e1b5b7
[ 1.436091] x14: 0000000000000000 x13: ffffffc084712860 x12: 0000000000000372
[ 1.436739] x11: 0000000000000126 x10: ffffffc08476a860 x9 : ffffffc084712860
[ 1.437389] x8 : 00000000ffffefff x7 : ffffffc08476a860 x6 : 0000000000000000
[ 1.438036] x5 : 000000000000bff4 x4 : 0000000000000000 x3 : 0000000000000000
[ 1.438683] x2 : 0000000000000000 x1 : ffffffc0846eb000 x0 : ffffff8000407b68
[ 1.439332] Call trace:
[ 1.439559] sched_numa_find_nth_cpu+0x2a0/0x488 (P)
[ 1.440016] smp_call_function_any+0xc8/0xd0
[ 1.440416] armv8_pmu_init+0x58/0x27c
[ 1.440770] armv8_cortex_a72_pmu_init+0x20/0x2c
[ 1.441199] arm_pmu_device_probe+0x1e4/0x5e8
[ 1.441603] armv8_pmu_device_probe+0x1c/0x28
[ 1.442007] platform_probe+0x5c/0xac
[ 1.442347] really_probe+0xbc/0x298
[ 1.442683] __driver_probe_device+0x78/0x12c
[ 1.443087] driver_probe_device+0xdc/0x160
[ 1.443475] __driver_attach+0x94/0x19c
[ 1.443833] bus_for_each_dev+0x74/0xd4
[ 1.444190] driver_attach+0x24/0x30
[ 1.444525] bus_add_driver+0xe4/0x208
[ 1.444874] driver_register+0x60/0x128
[ 1.445233] __platform_driver_register+0x24/0x30
[ 1.445662] armv8_pmu_driver_init+0x28/0x4c
[ 1.446059] do_one_initcall+0x44/0x25c
[ 1.446416] kernel_init_freeable+0x1dc/0x3bc
[ 1.446820] kernel_init+0x20/0x1d8
[ 1.447151] ret_from_fork+0x10/0x20
[ 1.447493] Code: 90022e21 f000e5f5 910de2b5 2a1703e2 (f8767803)
[ 1.448040] ---[ end trace 0000000000000000 ]---
[ 1.448483] note: swapper/0[1] exited with preempt_count 1
[ 1.449047] Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b
[ 1.449741] SMP: stopping secondary CPUs
[ 1.450105] Kernel Offset: disabled
[ 1.450419] CPU features: 0x000000,00080000,20002001,0400421b
[ 1.450935] Memory Limit: none
[ 1.451217] ---[ end Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b ]---
Yury: with the fix, the function returns cpu == nr_cpu_ids, and later in
smp_call_function_any ->
smp_call_function_single ->
generic_exec_single
we test the cpu for '>= nr_cpu_ids' and return -ENXIO. So everything is
handled correctly.
Fixes:
|
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Yicong Yang
|
52d15521eb |
sched/deadline: Don't count nr_running for dl_server proxy tasks
On CPU offline the kernel stalled with below call trace:
INFO: task kworker/0:1:11 blocked for more than 120 seconds.
cpuhp hold the cpu hotplug lock endless and stalled vmstat_shepherd.
This is because we count nr_running twice on cpuhp enqueuing and failed
the wait condition of cpuhp:
enqueue_task_fair() // pick cpuhp from idle, rq->nr_running = 0
dl_server_start()
[...]
add_nr_running() // rq->nr_running = 1
add_nr_running() // rq->nr_running = 2
[switch to cpuhp, waiting on balance_hotplug_wait()]
rcuwait_wait_event(rq->nr_running == 1 && ...) // failed, rq->nr_running=2
schedule() // wait again
It doesn't make sense to count the dl_server towards runnable tasks,
since it runs other tasks.
Fixes:
|
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kuyo chang
|
421fc59cf5 |
sched/deadline: Fix RT task potential starvation when expiry time passed
[Symptom]
The fair server mechanism, which is intended to prevent fair starvation
when higher-priority tasks monopolize the CPU.
Specifically, RT tasks on the runqueue may not be scheduled as expected.
[Analysis]
The log "sched: DL replenish lagged too much" triggered.
By memory dump of dl_server:
curr = 0xFFFFFF80D6A0AC00 (
dl_server = 0xFFFFFF83CD5B1470(
dl_runtime = 0x02FAF080,
dl_deadline = 0x3B9ACA00,
dl_period = 0x3B9ACA00,
dl_bw = 0xCCCC,
dl_density = 0xCCCC,
runtime = 0x02FAF080,
deadline = 0x0000082031EB0E80,
flags = 0x0,
dl_throttled = 0x0,
dl_yielded = 0x0,
dl_non_contending = 0x0,
dl_overrun = 0x0,
dl_server = 0x1,
dl_server_active = 0x1,
dl_defer = 0x1,
dl_defer_armed = 0x0,
dl_defer_running = 0x1,
dl_timer = (
node = (
expires = 0x000008199756E700),
_softexpires = 0x000008199756E700,
function = 0xFFFFFFDB9AF44D30 = dl_task_timer,
base = 0xFFFFFF83CD5A12C0,
state = 0x0,
is_rel = 0x0,
is_soft = 0x0,
clock_update_flags = 0x4,
clock = 0x000008204A496900,
- The timer expiration time (rq->curr->dl_server->dl_timer->expires)
is already in the past, indicating the timer has expired.
- The timer state (rq->curr->dl_server->dl_timer->state) is 0.
[Suspected Root Cause]
The relevant code flow in the throttle path of
update_curr_dl_se() as follows:
dequeue_dl_entity(dl_se, 0); // the DL entity is dequeued
if (unlikely(is_dl_boosted(dl_se) || !start_dl_timer(dl_se))) {
if (dl_server(dl_se)) // timer registration fails
enqueue_dl_entity(dl_se, ENQUEUE_REPLENISH);//enqueue immediately
...
}
The failure of `start_dl_timer` is caused by attempting to register a
timer with an expiration time that is already in the past. When this
situation persists, the code repeatedly re-enqueues the DL entity
without properly replenishing or restarting the timer, resulting in RT
task may not be scheduled as expected.
[Proposed Solution]:
Instead of immediately re-enqueuing the DL entity on timer registration
failure, this change ensures the DL entity is properly replenished and
the timer is restarted, preventing RT potential starvation.
Fixes:
|
||
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Juri Lelli
|
bb4700adc3 |
sched/deadline: Always stop dl-server before changing parameters
Commit |
||
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Huacai Chen
|
4717432dfd |
sched/deadline: Fix dl_server_stopped()
Commit |
||
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Andrea Righi
|
ddf7233fca |
sched/ext: Fix invalid task state transitions on class switch
When enabling a sched_ext scheduler, we may trigger invalid task state
transitions, resulting in warnings like the following (which can be
easily reproduced by running the hotplug selftest in a loop):
sched_ext: Invalid task state transition 0 -> 3 for fish[770]
WARNING: CPU: 18 PID: 787 at kernel/sched/ext.c:3862 scx_set_task_state+0x7c/0xc0
...
RIP: 0010:scx_set_task_state+0x7c/0xc0
...
Call Trace:
<TASK>
scx_enable_task+0x11f/0x2e0
switching_to_scx+0x24/0x110
scx_enable.isra.0+0xd14/0x13d0
bpf_struct_ops_link_create+0x136/0x1a0
__sys_bpf+0x1edd/0x2c30
__x64_sys_bpf+0x21/0x30
do_syscall_64+0xbb/0x370
entry_SYSCALL_64_after_hwframe+0x77/0x7f
This happens because we skip initialization for tasks that are already
dead (with their usage counter set to zero), but we don't exclude them
during the scheduling class transition phase.
Fix this by also skipping dead tasks during class swiching, preventing
invalid task state transitions.
Fixes:
|
||
|
Peter Zijlstra
|
99b773d720 |
sched/psi: Fix psi_seq initialization
With the seqcount moved out of the group into a global psi_seq,
re-initializing the seqcount on group creation is causing seqcount
corruption.
Fixes:
|
||
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Linus Torvalds
|
6a68cec16b |
sched_ext: Changes for v6.17
- Add support for cgroup "cpu.max" interface. - Code organization cleanup so that ext_idle.c doesn't depend on the source-file-inclusion build method of sched/. - Drop UP paths in accordance with sched core changes. - Documentation and other misc changes. -----BEGIN PGP SIGNATURE----- iIQEABYKACwWIQTfIjM1kS57o3GsC/uxYfJx3gVYGQUCaIqnxg4cdGpAa2VybmVs Lm9yZwAKCRCxYfJx3gVYGUh5AQC6YM7ggRPYRmy28m5B0nubpKtCHqPOAHSd/QbY MCiThgD+JuE9ewg3wYO/jvJx3NyIRB1McMnAaG59hf6R0Plh5Qo= =TeLF -----END PGP SIGNATURE----- Merge tag 'sched_ext-for-6.17' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext Pull sched_ext updates from Tejun Heo: - Add support for cgroup "cpu.max" interface - Code organization cleanup so that ext_idle.c doesn't depend on the source-file-inclusion build method of sched/ - Drop UP paths in accordance with sched core changes - Documentation and other misc changes * tag 'sched_ext-for-6.17' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext: sched_ext: Fix scx_bpf_reenqueue_local() reference sched_ext: Drop kfuncs marked for removal in 6.15 sched_ext, rcu: Eject BPF scheduler on RCU CPU stall panic kernel/sched/ext.c: fix typo "occured" -> "occurred" in comments sched_ext: Add support for cgroup bandwidth control interface sched_ext, sched/core: Factor out struct scx_task_group sched_ext: Return NULL in llc_span sched_ext: Always use SMP versions in kernel/sched/ext_idle.h sched_ext: Always use SMP versions in kernel/sched/ext_idle.c sched_ext: Always use SMP versions in kernel/sched/ext.h sched_ext: Always use SMP versions in kernel/sched/ext.c sched_ext: Documentation: Clarify time slice handling in task lifecycle sched_ext: Make scx_locked_rq() inline sched_ext: Make scx_rq_bypassing() inline sched_ext: idle: Make local functions static in ext_idle.c sched_ext: idle: Remove unnecessary ifdef in scx_bpf_cpu_node() |
||
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Linus Torvalds
|
63eb28bb14 |
ARM:
- Host driver for GICv5, the next generation interrupt controller for arm64, including support for interrupt routing, MSIs, interrupt translation and wired interrupts. - Use FEAT_GCIE_LEGACY on GICv5 systems to virtualize GICv3 VMs on GICv5 hardware, leveraging the legacy VGIC interface. - Userspace control of the 'nASSGIcap' GICv3 feature, allowing userspace to disable support for SGIs w/o an active state on hardware that previously advertised it unconditionally. - Map supporting endpoints with cacheable memory attributes on systems with FEAT_S2FWB and DIC where KVM no longer needs to perform cache maintenance on the address range. - Nested support for FEAT_RAS and FEAT_DoubleFault2, allowing the guest hypervisor to inject external aborts into an L2 VM and take traps of masked external aborts to the hypervisor. - Convert more system register sanitization to the config-driven implementation. - Fixes to the visibility of EL2 registers, namely making VGICv3 system registers accessible through the VGIC device instead of the ONE_REG vCPU ioctls. - Various cleanups and minor fixes. LoongArch: - Add stat information for in-kernel irqchip - Add tracepoints for CPUCFG and CSR emulation exits - Enhance in-kernel irqchip emulation - Various cleanups. RISC-V: - Enable ring-based dirty memory tracking - Improve perf kvm stat to report interrupt events - Delegate illegal instruction trap to VS-mode - MMU improvements related to upcoming nested virtualization s390x - Fixes x86: - Add CONFIG_KVM_IOAPIC for x86 to allow disabling support for I/O APIC, PIC, and PIT emulation at compile time. - Share device posted IRQ code between SVM and VMX and harden it against bugs and runtime errors. - Use vcpu_idx, not vcpu_id, for GA log tag/metadata, to make lookups O(1) instead of O(n). - For MMIO stale data mitigation, track whether or not a vCPU has access to (host) MMIO based on whether the page tables have MMIO pfns mapped; using VFIO is prone to false negatives - Rework the MSR interception code so that the SVM and VMX APIs are more or less identical. - Recalculate all MSR intercepts from scratch on MSR filter changes, instead of maintaining shadow bitmaps. - Advertise support for LKGS (Load Kernel GS base), a new instruction that's loosely related to FRED, but is supported and enumerated independently. - Fix a user-triggerable WARN that syzkaller found by setting the vCPU in INIT_RECEIVED state (aka wait-for-SIPI), and then putting the vCPU into VMX Root Mode (post-VMXON). Trying to detect every possible path leading to architecturally forbidden states is hard and even risks breaking userspace (if it goes from valid to valid state but passes through invalid states), so just wait until KVM_RUN to detect that the vCPU state isn't allowed. - Add KVM_X86_DISABLE_EXITS_APERFMPERF to allow disabling interception of APERF/MPERF reads, so that a "properly" configured VM can access APERF/MPERF. This has many caveats (APERF/MPERF cannot be zeroed on vCPU creation or saved/restored on suspend and resume, or preserved over thread migration let alone VM migration) but can be useful whenever you're interested in letting Linux guests see the effective physical CPU frequency in /proc/cpuinfo. - Reject KVM_SET_TSC_KHZ for vm file descriptors if vCPUs have been created, as there's no known use case for changing the default frequency for other VM types and it goes counter to the very reason why the ioctl was added to the vm file descriptor. And also, there would be no way to make it work for confidential VMs with a "secure" TSC, so kill two birds with one stone. - Dynamically allocation the shadow MMU's hashed page list, and defer allocating the hashed list until it's actually needed (the TDP MMU doesn't use the list). - Extract many of KVM's helpers for accessing architectural local APIC state to common x86 so that they can be shared by guest-side code for Secure AVIC. - Various cleanups and fixes. x86 (Intel): - Preserve the host's DEBUGCTL.FREEZE_IN_SMM when running the guest. Failure to honor FREEZE_IN_SMM can leak host state into guests. - Explicitly check vmcs12.GUEST_DEBUGCTL on nested VM-Enter to prevent L1 from running L2 with features that KVM doesn't support, e.g. BTF. x86 (AMD): - WARN and reject loading kvm-amd.ko instead of panicking the kernel if the nested SVM MSRPM offsets tracker can't handle an MSR (which is pretty much a static condition and therefore should never happen, but still). - Fix a variety of flaws and bugs in the AVIC device posted IRQ code. - Inhibit AVIC if a vCPU's ID is too big (relative to what hardware supports) instead of rejecting vCPU creation. - Extend enable_ipiv module param support to SVM, by simply leaving IsRunning clear in the vCPU's physical ID table entry. - Disable IPI virtualization, via enable_ipiv, if the CPU is affected by erratum #1235, to allow (safely) enabling AVIC on such CPUs. - Request GA Log interrupts if and only if the target vCPU is blocking, i.e. only if KVM needs a notification in order to wake the vCPU. - Intercept SPEC_CTRL on AMD if the MSR shouldn't exist according to the vCPU's CPUID model. - Accept any SNP policy that is accepted by the firmware with respect to SMT and single-socket restrictions. An incompatible policy doesn't put the kernel at risk in any way, so there's no reason for KVM to care. - Drop a superfluous WBINVD (on all CPUs!) when destroying a VM and use WBNOINVD instead of WBINVD when possible for SEV cache maintenance. - When reclaiming memory from an SEV guest, only do cache flushes on CPUs that have ever run a vCPU for the guest, i.e. don't flush the caches for CPUs that can't possibly have cache lines with dirty, encrypted data. Generic: - Rework irqbypass to track/match producers and consumers via an xarray instead of a linked list. Using a linked list leads to O(n^2) insertion times, which is hugely problematic for use cases that create large numbers of VMs. Such use cases typically don't actually use irqbypass, but eliminating the pointless registration is a future problem to solve as it likely requires new uAPI. - Track irqbypass's "token" as "struct eventfd_ctx *" instead of a "void *", to avoid making a simple concept unnecessarily difficult to understand. - Decouple device posted IRQs from VFIO device assignment, as binding a VM to a VFIO group is not a requirement for enabling device posted IRQs. - Clean up and document/comment the irqfd assignment code. - Disallow binding multiple irqfds to an eventfd with a priority waiter, i.e. ensure an eventfd is bound to at most one irqfd through the entire host, and add a selftest to verify eventfd:irqfd bindings are globally unique. - Add a tracepoint for KVM_SET_MEMORY_ATTRIBUTES to help debug issues related to private <=> shared memory conversions. - Drop guest_memfd's .getattr() implementation as the VFS layer will call generic_fillattr() if inode_operations.getattr is NULL. - Fix issues with dirty ring harvesting where KVM doesn't bound the processing of entries in any way, which allows userspace to keep KVM in a tight loop indefinitely. - Kill off kvm_arch_{start,end}_assignment() and x86's associated tracking, now that KVM no longer uses assigned_device_count as a heuristic for either irqbypass usage or MDS mitigation. Selftests: - Fix a comment typo. - Verify KVM is loaded when getting any KVM module param so that attempting to run a selftest without kvm.ko loaded results in a SKIP message about KVM not being loaded/enabled (versus some random parameter not existing). - Skip tests that hit EACCES when attempting to access a file, and rpint a "Root required?" help message. In most cases, the test just needs to be run with elevated permissions. -----BEGIN PGP SIGNATURE----- iQFIBAABCAAyFiEE8TM4V0tmI4mGbHaCv/vSX3jHroMFAmiKXMgUHHBib256aW5p QHJlZGhhdC5jb20ACgkQv/vSX3jHroMhMQf/QDhC/CP1aGXph2whuyeD2NMqPKiU 9KdnDNST+ftPwjg9QxZ9mTaa8zeVz/wly6XlxD9OQHy+opM1wcys3k0GZAFFEEQm YrThgURdzEZ3nwJZgb+m0t4wjJQtpiFIBwAf7qq6z1VrqQBEmHXJ/8QxGuqO+BNC j5q/X+q6KZwehKI6lgFBrrOKWFaxqhnRAYfW6rGBxRXxzTJuna37fvDpodQnNceN zOiq+avfriUMArTXTqOteJNKU0229HjiPSnjILLnFQ+B3akBlwNG0jk7TMaAKR6q IZWG1EIS9q1BAkGXaw6DE1y6d/YwtXCR5qgAIkiGwaPt5yj9Oj6kRN2Ytw== =j2At -----END PGP SIGNATURE----- Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm Pull kvm updates from Paolo Bonzini: "ARM: - Host driver for GICv5, the next generation interrupt controller for arm64, including support for interrupt routing, MSIs, interrupt translation and wired interrupts - Use FEAT_GCIE_LEGACY on GICv5 systems to virtualize GICv3 VMs on GICv5 hardware, leveraging the legacy VGIC interface - Userspace control of the 'nASSGIcap' GICv3 feature, allowing userspace to disable support for SGIs w/o an active state on hardware that previously advertised it unconditionally - Map supporting endpoints with cacheable memory attributes on systems with FEAT_S2FWB and DIC where KVM no longer needs to perform cache maintenance on the address range - Nested support for FEAT_RAS and FEAT_DoubleFault2, allowing the guest hypervisor to inject external aborts into an L2 VM and take traps of masked external aborts to the hypervisor - Convert more system register sanitization to the config-driven implementation - Fixes to the visibility of EL2 registers, namely making VGICv3 system registers accessible through the VGIC device instead of the ONE_REG vCPU ioctls - Various cleanups and minor fixes LoongArch: - Add stat information for in-kernel irqchip - Add tracepoints for CPUCFG and CSR emulation exits - Enhance in-kernel irqchip emulation - Various cleanups RISC-V: - Enable ring-based dirty memory tracking - Improve perf kvm stat to report interrupt events - Delegate illegal instruction trap to VS-mode - MMU improvements related to upcoming nested virtualization s390x - Fixes x86: - Add CONFIG_KVM_IOAPIC for x86 to allow disabling support for I/O APIC, PIC, and PIT emulation at compile time - Share device posted IRQ code between SVM and VMX and harden it against bugs and runtime errors - Use vcpu_idx, not vcpu_id, for GA log tag/metadata, to make lookups O(1) instead of O(n) - For MMIO stale data mitigation, track whether or not a vCPU has access to (host) MMIO based on whether the page tables have MMIO pfns mapped; using VFIO is prone to false negatives - Rework the MSR interception code so that the SVM and VMX APIs are more or less identical - Recalculate all MSR intercepts from scratch on MSR filter changes, instead of maintaining shadow bitmaps - Advertise support for LKGS (Load Kernel GS base), a new instruction that's loosely related to FRED, but is supported and enumerated independently - Fix a user-triggerable WARN that syzkaller found by setting the vCPU in INIT_RECEIVED state (aka wait-for-SIPI), and then putting the vCPU into VMX Root Mode (post-VMXON). Trying to detect every possible path leading to architecturally forbidden states is hard and even risks breaking userspace (if it goes from valid to valid state but passes through invalid states), so just wait until KVM_RUN to detect that the vCPU state isn't allowed - Add KVM_X86_DISABLE_EXITS_APERFMPERF to allow disabling interception of APERF/MPERF reads, so that a "properly" configured VM can access APERF/MPERF. This has many caveats (APERF/MPERF cannot be zeroed on vCPU creation or saved/restored on suspend and resume, or preserved over thread migration let alone VM migration) but can be useful whenever you're interested in letting Linux guests see the effective physical CPU frequency in /proc/cpuinfo - Reject KVM_SET_TSC_KHZ for vm file descriptors if vCPUs have been created, as there's no known use case for changing the default frequency for other VM types and it goes counter to the very reason why the ioctl was added to the vm file descriptor. And also, there would be no way to make it work for confidential VMs with a "secure" TSC, so kill two birds with one stone - Dynamically allocation the shadow MMU's hashed page list, and defer allocating the hashed list until it's actually needed (the TDP MMU doesn't use the list) - Extract many of KVM's helpers for accessing architectural local APIC state to common x86 so that they can be shared by guest-side code for Secure AVIC - Various cleanups and fixes x86 (Intel): - Preserve the host's DEBUGCTL.FREEZE_IN_SMM when running the guest. Failure to honor FREEZE_IN_SMM can leak host state into guests - Explicitly check vmcs12.GUEST_DEBUGCTL on nested VM-Enter to prevent L1 from running L2 with features that KVM doesn't support, e.g. BTF x86 (AMD): - WARN and reject loading kvm-amd.ko instead of panicking the kernel if the nested SVM MSRPM offsets tracker can't handle an MSR (which is pretty much a static condition and therefore should never happen, but still) - Fix a variety of flaws and bugs in the AVIC device posted IRQ code - Inhibit AVIC if a vCPU's ID is too big (relative to what hardware supports) instead of rejecting vCPU creation - Extend enable_ipiv module param support to SVM, by simply leaving IsRunning clear in the vCPU's physical ID table entry - Disable IPI virtualization, via enable_ipiv, if the CPU is affected by erratum #1235, to allow (safely) enabling AVIC on such CPUs - Request GA Log interrupts if and only if the target vCPU is blocking, i.e. only if KVM needs a notification in order to wake the vCPU - Intercept SPEC_CTRL on AMD if the MSR shouldn't exist according to the vCPU's CPUID model - Accept any SNP policy that is accepted by the firmware with respect to SMT and single-socket restrictions. An incompatible policy doesn't put the kernel at risk in any way, so there's no reason for KVM to care - Drop a superfluous WBINVD (on all CPUs!) when destroying a VM and use WBNOINVD instead of WBINVD when possible for SEV cache maintenance - When reclaiming memory from an SEV guest, only do cache flushes on CPUs that have ever run a vCPU for the guest, i.e. don't flush the caches for CPUs that can't possibly have cache lines with dirty, encrypted data Generic: - Rework irqbypass to track/match producers and consumers via an xarray instead of a linked list. Using a linked list leads to O(n^2) insertion times, which is hugely problematic for use cases that create large numbers of VMs. Such use cases typically don't actually use irqbypass, but eliminating the pointless registration is a future problem to solve as it likely requires new uAPI - Track irqbypass's "token" as "struct eventfd_ctx *" instead of a "void *", to avoid making a simple concept unnecessarily difficult to understand - Decouple device posted IRQs from VFIO device assignment, as binding a VM to a VFIO group is not a requirement for enabling device posted IRQs - Clean up and document/comment the irqfd assignment code - Disallow binding multiple irqfds to an eventfd with a priority waiter, i.e. ensure an eventfd is bound to at most one irqfd through the entire host, and add a selftest to verify eventfd:irqfd bindings are globally unique - Add a tracepoint for KVM_SET_MEMORY_ATTRIBUTES to help debug issues related to private <=> shared memory conversions - Drop guest_memfd's .getattr() implementation as the VFS layer will call generic_fillattr() if inode_operations.getattr is NULL - Fix issues with dirty ring harvesting where KVM doesn't bound the processing of entries in any way, which allows userspace to keep KVM in a tight loop indefinitely - Kill off kvm_arch_{start,end}_assignment() and x86's associated tracking, now that KVM no longer uses assigned_device_count as a heuristic for either irqbypass usage or MDS mitigation Selftests: - Fix a comment typo - Verify KVM is loaded when getting any KVM module param so that attempting to run a selftest without kvm.ko loaded results in a SKIP message about KVM not being loaded/enabled (versus some random parameter not existing) - Skip tests that hit EACCES when attempting to access a file, and print a "Root required?" help message. In most cases, the test just needs to be run with elevated permissions" * tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (340 commits) Documentation: KVM: Use unordered list for pre-init VGIC registers RISC-V: KVM: Avoid re-acquiring memslot in kvm_riscv_gstage_map() RISC-V: KVM: Use find_vma_intersection() to search for intersecting VMAs RISC-V: perf/kvm: Add reporting of interrupt events RISC-V: KVM: Enable ring-based dirty memory tracking RISC-V: KVM: Fix inclusion of Smnpm in the guest ISA bitmap RISC-V: KVM: Delegate illegal instruction fault to VS mode RISC-V: KVM: Pass VMID as parameter to kvm_riscv_hfence_xyz() APIs RISC-V: KVM: Factor-out g-stage page table management RISC-V: KVM: Add vmid field to struct kvm_riscv_hfence RISC-V: KVM: Introduce struct kvm_gstage_mapping RISC-V: KVM: Factor-out MMU related declarations into separate headers RISC-V: KVM: Use ncsr_xyz() in kvm_riscv_vcpu_trap_redirect() RISC-V: KVM: Implement kvm_arch_flush_remote_tlbs_range() RISC-V: KVM: Don't flush TLB when PTE is unchanged RISC-V: KVM: Replace KVM_REQ_HFENCE_GVMA_VMID_ALL with KVM_REQ_TLB_FLUSH RISC-V: KVM: Rename and move kvm_riscv_local_tlb_sanitize() RISC-V: KVM: Drop the return value of kvm_riscv_vcpu_aia_init() RISC-V: KVM: Check kvm_riscv_vcpu_alloc_vector_context() return value KVM: arm64: selftests: Add FEAT_RAS EL2 registers to get-reg-list ... |
||
|
Linus Torvalds
|
4ff261e725 |
Runtime verification changes for 6.17
- Added Linear temporal logic monitors for RT application
Real-time applications may have design flaws causing them to have
unexpected latency. For example, the applications may raise page faults, or
may be blocked trying to take a mutex without priority inheritance.
However, while attempting to implement DA monitors for these real-time
rules, deterministic automaton is found to be inappropriate as the
specification language. The automaton is complicated, hard to understand,
and error-prone.
For these cases, linear temporal logic is found to be more suitable. The
LTL is more concise and intuitive.
- Make printk_deferred() public
The new monitors needed access to printk_deferred(). Make them visible for
the entire kernel.
- Add a vpanic() to allow for va_list to be passed to panic.
- Add rtapp container monitor.
A collection of monitors that check for common problems with real-time
applications that cause unexpected latency.
- Add page fault tracepoints to risc-v
These tracepoints are necessary to for the RV monitor to run on risc-v.
- Fix the behaviour of the rv tool with -s and idle tasks.
- Allow the rv tool to gracefully terminate with SIGTERM
- Adjusts dot2c not to create lines over 100 columns
- Properly order nested monitors in the RV Kconfig file
- Return the registration error in all DA monitor instead of 0
- Update and add new sched collection monitors
Replace tss and sncid monitors with more complete sts:
Not only prove that switches occur in scheduling context and scheduling
needs interrupt disabled but also that each call to the scheduler
disables interrupts to (optionally) switch.
New monitor: nrp
Preemption requires need resched which is cleared by any switch
(includes a non optimal workaround for /nested/ preemptions)
New monitor: sssw
suspension requires setting the task to sleepable and, after the
switch occurs, the task requires a wakeup to come back to runnable
New monitor: opid
waking and need-resched operations occur with interrupts and
preemption disabled or in IRQ without explicitly disabling preemption
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Merge tag 'trace-rv-6.17' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace
Pull runtime verification updates from Steven Rostedt:
- Added Linear temporal logic monitors for RT application
Real-time applications may have design flaws causing them to have
unexpected latency. For example, the applications may raise page
faults, or may be blocked trying to take a mutex without priority
inheritance.
However, while attempting to implement DA monitors for these
real-time rules, deterministic automaton is found to be inappropriate
as the specification language. The automaton is complicated, hard to
understand, and error-prone.
For these cases, linear temporal logic is found to be more suitable.
The LTL is more concise and intuitive.
- Make printk_deferred() public
The new monitors needed access to printk_deferred(). Make them
visible for the entire kernel.
- Add a vpanic() to allow for va_list to be passed to panic.
- Add rtapp container monitor.
A collection of monitors that check for common problems with
real-time applications that cause unexpected latency.
- Add page fault tracepoints to risc-v
These tracepoints are necessary to for the RV monitor to run on
risc-v.
- Fix the behaviour of the rv tool with -s and idle tasks.
- Allow the rv tool to gracefully terminate with SIGTERM
- Adjusts dot2c not to create lines over 100 columns
- Properly order nested monitors in the RV Kconfig file
- Return the registration error in all DA monitor instead of 0
- Update and add new sched collection monitors
Replace tss and sncid monitors with more complete sts:
Not only prove that switches occur in scheduling context and scheduling
needs interrupt disabled but also that each call to the scheduler
disables interrupts to (optionally) switch.
New monitor: nrp
Preemption requires need resched which is cleared by any switch
(includes a non optimal workaround for /nested/ preemptions)
New monitor: sssw
suspension requires setting the task to sleepable and, after the
switch occurs, the task requires a wakeup to come back to runnable
New monitor: opid
waking and need-resched operations occur with interrupts and
preemption disabled or in IRQ without explicitly disabling
preemption"
* tag 'trace-rv-6.17' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: (48 commits)
rv: Add opid per-cpu monitor
rv: Add nrp and sssw per-task monitors
rv: Replace tss and sncid monitors with more complete sts
sched: Adapt sched tracepoints for RV task model
rv: Retry when da monitor detects race conditions
rv: Adjust monitor dependencies
rv: Use strings in da monitors tracepoints
rv: Remove trailing whitespace from tracepoint string
rv: Add da_handle_start_run_event_ to per-task monitors
rv: Fix wrong type cast in reactors_show() and monitor_reactor_show()
rv: Fix wrong type cast in monitors_show()
rv: Remove struct rv_monitor::reacting
rv: Remove rv_reactor's reference counter
rv: Merge struct rv_reactor_def into struct rv_reactor
rv: Merge struct rv_monitor_def into struct rv_monitor
rv: Remove unused field in struct rv_monitor_def
rv: Return init error when registering monitors
verification/rvgen: Organise Kconfig entries for nested monitors
tools/dot2c: Fix generated files going over 100 column limit
tools/rv: Stop gracefully also on SIGTERM
...
|
||
|
Linus Torvalds
|
bf76f23aa1 |
Scheduler updates for v6.17:
Core scheduler changes:
- Better tracking of maximum lag of tasks in presence of different
slices duration, for better handling of lag in the fair
scheduler. (Vincent Guittot)
- Clean up and standardize #if/#else/#endif markers throughout
the entire scheduler code base (Ingo Molnar)
- Make SMP unconditional: build the SMP scheduler's
data structures and logic on UP kernel too, even though
they are not used, to simplify the scheduler and remove
around 200 #ifdef/[#else]/#endif blocks from the
scheduler. (Ingo Molnar)
- Reorganize cgroup bandwidth control interface handling
for better interfacing with sched_ext (Tejun Heo)
Balancing:
- Bump sd->max_newidle_lb_cost when newidle balance fails (Chris Mason)
- Remove sched_domain_topology_level::flags to simplify the code (Prateek Nayak)
- Simplify and clean up build_sched_topology() (Li Chen)
- Optimize build_sched_topology() on large machines (Li Chen)
Real-time scheduling:
- Add initial version of proxy execution: a mechanism for mutex-owning
tasks to inherit the scheduling context of higher priority waiters.
Currently limited to a single runqueue and conditional on CONFIG_EXPERT,
and other limitations. (John Stultz, Peter Zijlstra, Valentin Schneider)
- Deadline scheduler (Juri Lelli):
- Fix dl_servers initialization order (Juri Lelli)
- Fix DL scheduler's root domain reinitialization logic (Juri Lelli)
- Fix accounting bugs after global limits change (Juri Lelli)
- Fix scalability regression by implementing less agressive dl_server handling
(Peter Zijlstra)
PSI:
- Improve scalability by optimizing psi_group_change() cpu_clock() usage
(Peter Zijlstra)
Rust changes:
- Make Task, CondVar and PollCondVar methods inline to avoid unnecessary
function calls (Kunwu Chan, Panagiotis Foliadis)
- Add might_sleep() support for Rust code: Rust's "#[track_caller]"
mechanism is used so that Rust's might_sleep() doesn't need to be
defined as a macro (Fujita Tomonori)
- Introduce file_from_location() (Boqun Feng)
Debugging & instrumentation:
- Make clangd usable with scheduler source code files again (Peter Zijlstra)
- tools: Add root_domains_dump.py which dumps root domains info (Juri Lelli)
- tools: Add dl_bw_dump.py for printing bandwidth accounting info (Juri Lelli)
Misc cleanups & fixes:
- Remove play_idle() (Feng Lee)
- Fix check_preemption_disabled() (Sebastian Andrzej Siewior)
- Do not call __put_task_struct() on RT if pi_blocked_on is set
(Luis Claudio R. Goncalves)
- Correct the comment in place_entity() (wang wei)
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'sched-core-2025-07-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler updates from Ingo Molnar:
"Core scheduler changes:
- Better tracking of maximum lag of tasks in presence of different
slices duration, for better handling of lag in the fair scheduler
(Vincent Guittot)
- Clean up and standardize #if/#else/#endif markers throughout the
entire scheduler code base (Ingo Molnar)
- Make SMP unconditional: build the SMP scheduler's data structures
and logic on UP kernel too, even though they are not used, to
simplify the scheduler and remove around 200 #ifdef/[#else]/#endif
blocks from the scheduler (Ingo Molnar)
- Reorganize cgroup bandwidth control interface handling for better
interfacing with sched_ext (Tejun Heo)
Balancing:
- Bump sd->max_newidle_lb_cost when newidle balance fails (Chris
Mason)
- Remove sched_domain_topology_level::flags to simplify the code
(Prateek Nayak)
- Simplify and clean up build_sched_topology() (Li Chen)
- Optimize build_sched_topology() on large machines (Li Chen)
Real-time scheduling:
- Add initial version of proxy execution: a mechanism for
mutex-owning tasks to inherit the scheduling context of higher
priority waiters.
Currently limited to a single runqueue and conditional on
CONFIG_EXPERT, and other limitations (John Stultz, Peter Zijlstra,
Valentin Schneider)
- Deadline scheduler (Juri Lelli):
- Fix dl_servers initialization order (Juri Lelli)
- Fix DL scheduler's root domain reinitialization logic (Juri
Lelli)
- Fix accounting bugs after global limits change (Juri Lelli)
- Fix scalability regression by implementing less agressive
dl_server handling (Peter Zijlstra)
PSI:
- Improve scalability by optimizing psi_group_change() cpu_clock()
usage (Peter Zijlstra)
Rust changes:
- Make Task, CondVar and PollCondVar methods inline to avoid
unnecessary function calls (Kunwu Chan, Panagiotis Foliadis)
- Add might_sleep() support for Rust code: Rust's "#[track_caller]"
mechanism is used so that Rust's might_sleep() doesn't need to be
defined as a macro (Fujita Tomonori)
- Introduce file_from_location() (Boqun Feng)
Debugging & instrumentation:
- Make clangd usable with scheduler source code files again (Peter
Zijlstra)
- tools: Add root_domains_dump.py which dumps root domains info (Juri
Lelli)
- tools: Add dl_bw_dump.py for printing bandwidth accounting info
(Juri Lelli)
Misc cleanups & fixes:
- Remove play_idle() (Feng Lee)
- Fix check_preemption_disabled() (Sebastian Andrzej Siewior)
- Do not call __put_task_struct() on RT if pi_blocked_on is set (Luis
Claudio R. Goncalves)
- Correct the comment in place_entity() (wang wei)"
* tag 'sched-core-2025-07-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (84 commits)
sched/idle: Remove play_idle()
sched: Do not call __put_task_struct() on rt if pi_blocked_on is set
sched: Start blocked_on chain processing in find_proxy_task()
sched: Fix proxy/current (push,pull)ability
sched: Add an initial sketch of the find_proxy_task() function
sched: Fix runtime accounting w/ split exec & sched contexts
sched: Move update_curr_task logic into update_curr_se
locking/mutex: Add p->blocked_on wrappers for correctness checks
locking/mutex: Rework task_struct::blocked_on
sched: Add CONFIG_SCHED_PROXY_EXEC & boot argument to enable/disable
sched/topology: Remove sched_domain_topology_level::flags
x86/smpboot: avoid SMT domain attach/destroy if SMT is not enabled
x86/smpboot: moves x86_topology to static initialize and truncate
x86/smpboot: remove redundant CONFIG_SCHED_SMT
smpboot: introduce SDTL_INIT() helper to tidy sched topology setup
tools/sched: Add dl_bw_dump.py for printing bandwidth accounting info
tools/sched: Add root_domains_dump.py which dumps root domains info
sched/deadline: Fix accounting after global limits change
sched/deadline: Reset extra_bw to max_bw when clearing root domains
sched/deadline: Initialize dl_servers after SMP
...
|
||
|
Linus Torvalds
|
78bb43e51b |
Updates for the generic entry code:
- Split the code into syscall and exception/interrupt parts to ease the
conversion of ARM[64] to the generic entry infrastructure
- Extend syscall user dispatching to support a single intercepted range
instead of the default single non-intercepted range. That allows
monitoring/analysis of a specific executable range, e.g. a library, and
also provides flexibility for sandboxing scenarios.
- Cleanup and extend the user dispatch selftest
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Merge tag 'core-entry-2025-07-29' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull generic entry code updates from Thomas Gleixner:
- Split the code into syscall and exception/interrupt parts to ease the
conversion of ARM[64] to the generic entry infrastructure
- Extend syscall user dispatching to support a single intercepted range
instead of the default single non-intercepted range. That allows
monitoring/analysis of a specific executable range, e.g. a library,
and also provides flexibility for sandboxing scenarios
- Cleanup and extend the user dispatch selftest
* tag 'core-entry-2025-07-29' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
entry: Split generic entry into generic exception and syscall entry
selftests: Add tests for PR_SYS_DISPATCH_INCLUSIVE_ON
syscall_user_dispatch: Add PR_SYS_DISPATCH_INCLUSIVE_ON
selftests: Fix errno checking in syscall_user_dispatch test
|
||
|
Paolo Bonzini
|
f02b1bcc73 |
Merge tag 'kvm-x86-irqs-6.17' of https://github.com/kvm-x86/linux into HEAD
KVM IRQ changes for 6.17 - Rework irqbypass to track/match producers and consumers via an xarray instead of a linked list. Using a linked list leads to O(n^2) insertion times, which is hugely problematic for use cases that create large numbers of VMs. Such use cases typically don't actually use irqbypass, but eliminating the pointless registration is a future problem to solve as it likely requires new uAPI. - Track irqbypass's "token" as "struct eventfd_ctx *" instead of a "void *", to avoid making a simple concept unnecessarily difficult to understand. - Add CONFIG_KVM_IOAPIC for x86 to allow disabling support for I/O APIC, PIC, and PIT emulation at compile time. - Drop x86's irq_comm.c, and move a pile of IRQ related code into irq.c. - Fix a variety of flaws and bugs in the AVIC device posted IRQ code. - Inhibited AVIC if a vCPU's ID is too big (relative to what hardware supports) instead of rejecting vCPU creation. - Extend enable_ipiv module param support to SVM, by simply leaving IsRunning clear in the vCPU's physical ID table entry. - Disable IPI virtualization, via enable_ipiv, if the CPU is affected by erratum #1235, to allow (safely) enabling AVIC on such CPUs. - Dedup x86's device posted IRQ code, as the vast majority of functionality can be shared verbatime between SVM and VMX. - Harden the device posted IRQ code against bugs and runtime errors. - Use vcpu_idx, not vcpu_id, for GA log tag/metadata, to make lookups O(1) instead of O(n). - Generate GA Log interrupts if and only if the target vCPU is blocking, i.e. only if KVM needs a notification in order to wake the vCPU. - Decouple device posted IRQs from VFIO device assignment, as binding a VM to a VFIO group is not a requirement for enabling device posted IRQs. - Clean up and document/comment the irqfd assignment code. - Disallow binding multiple irqfds to an eventfd with a priority waiter, i.e. ensure an eventfd is bound to at most one irqfd through the entire host, and add a selftest to verify eventfd:irqfd bindings are globally unique. |
||
|
Gabriele Monaco
|
adcc3bfa88 |
sched: Adapt sched tracepoints for RV task model
Add the following tracepoint:
* sched_set_need_resched(tsk, cpu, tif)
Called when a task is set the need resched [lazy] flag
Remove the unused ip parameter from sched_entry and sched_exit and alter
sched_entry to have a value of preempt consistent with the one used in
sched_switch.
Also adapt all monitors using sched_{entry,exit} to avoid breaking build.
These tracepoints are useful to describe the Linux task model and are
adapted from the patches by Daniel Bristot de Oliveira
(https://bristot.me/linux-task-model/).
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Nam Cao <namcao@linutronix.de>
Cc: Tomas Glozar <tglozar@redhat.com>
Cc: Juri Lelli <jlelli@redhat.com>
Cc: Clark Williams <williams@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
Link: https://lore.kernel.org/20250728135022.255578-7-gmonaco@redhat.com
Signed-off-by: Gabriele Monaco <gmonaco@redhat.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
|
||
|
Linus Torvalds
|
62347e2790 |
A single fix for the scheduler. A recent commit changed the runqueue
counter nr_uninterruptible to an unsigned int. Due to the fact that the counters are not updated on migration of a uninterruptble task to a different CPU, these counters can exceed INT_MAX. The counter is cast to long in the load average calculation, which means that the cast expands into negative space resulting in bogus load average values. Convert it back to unsigned long to fix this. -----BEGIN PGP SIGNATURE----- iQJHBAABCgAxFiEEQp8+kY+LLUocC4bMphj1TA10mKEFAmh82RYTHHRnbHhAbGlu dXRyb25peC5kZQAKCRCmGPVMDXSYoXNlEACyQxl/OCXSmKpcxrIvMjnalXh3Ibs2 KqbZ3MA/hY1ZWhSKXBDMv8hkxE00PY8WXsPDtLeRz0n6GegbUx4zVsUQpzn24gRe uEl+qIuANaz5uMu2qlmQwSuxVQ0SDqLVFObrNgKQ554jJckjXKcgvrBjwczTw9lJ u6yTVLrknf0IsbQ79yxToaNf6jD3HcSIGX06Hs4EYucPzYd54VScr6LGGwux3rmI CN0RSA9RduUzcf/aKhe9/tmM6oss4tdByNuVSdx/yZ5QvVw5oOrWdI8sU0BlZsrC IjvqLvvLFKRPZre24UeFnIVxhtv+cwPXxrA6tR/SM2eUbHKzU8jHz2TlPu8xwOwb sZMMBjPx1Y+fpVQoGxEC1cEWbCUPSyQ7NGN2uS3Quk4XoQLRz6t//B+63rT65bfV wMAZpsgZ9/c23yDuPG11XxBMQYVbS0sFyLDymBC93Co8vh8PowDIf2xmgPFLxM78 HdOCCsHsBPqZutQGQ7/qw//e7T/9fv0MDP8D4fuyLrhUdvBAvGHZp85T4YmOUcjp bTTE28Rw1sBgdAnTNjGWfwRN7Hwc1DzaLh40Um+nnjMA+yG9uq7gjTYDx4w6W/EA V70tx9tfJOM11g/qfIURkJDpf8PezJ3KHg1ZOiPn9e+I08LoPVMeIqbFEnJ9VAc7 VStWpQd+SG99AQ== =Aqcr -----END PGP SIGNATURE----- Merge tag 'sched-urgent-2025-07-20' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull scheduler fix from Thomas Gleixner: "A single fix for the scheduler. A recent commit changed the runqueue counter nr_uninterruptible to an unsigned int. Due to the fact that the counters are not updated on migration of a uninterruptble task to a different CPU, these counters can exceed INT_MAX. The counter is cast to long in the load average calculation, which means that the cast expands into negative space resulting in bogus load average values. Convert it back to unsigned long to fix this. * tag 'sched-urgent-2025-07-20' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: sched: Change nr_uninterruptible type to unsigned long |
||
|
Linus Torvalds
|
bf61759db4 |
sched_ext: Fixes for v6.16-rc6
- Fix handling of migration disabled tasks in default idle selection. - update_locked_rq() called __this_cpu_write() spuriously with NULL when @rq was not locked. As the writes were spurious, it didn't break anything directly. However, the function could be called in a preemptible leading to a context warning in __this_cpu_write(). Skip the spurious NULL writes. - Selftest fix on UP. -----BEGIN PGP SIGNATURE----- iIQEABYKACwWIQTfIjM1kS57o3GsC/uxYfJx3gVYGQUCaHvPZw4cdGpAa2VybmVs Lm9yZwAKCRCxYfJx3gVYGabMAP4jSAr4gYWEBOUaD9btwnPxZwlSiAEQtqBDBVRb /UunFAD/WBwUPk/u7BchLHjuH3sYW5gQb40kbtUnmNvB+RNUUgc= =3WAD -----END PGP SIGNATURE----- Merge tag 'sched_ext-for-6.16-rc6-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext Pull sched_ext fixes from Tejun Heo: - Fix handling of migration disabled tasks in default idle selection - update_locked_rq() called __this_cpu_write() spuriously with NULL when @rq was not locked. As the writes were spurious, it didn't break anything directly. However, the function could be called in a preemptible leading to a context warning in __this_cpu_write(). Skip the spurious NULL writes. - Selftest fix on UP * tag 'sched_ext-for-6.16-rc6-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext: sched_ext: idle: Handle migration-disabled tasks in idle selection sched/ext: Prevent update_locked_rq() calls with NULL rq selftests/sched_ext: Fix exit selftest hang on UP |
||
|
Andrea Righi
|
06efc9fe0b |
sched_ext: idle: Handle migration-disabled tasks in idle selection
When SCX_OPS_ENQ_MIGRATION_DISABLED is enabled, migration-disabled tasks
are also routed to ops.enqueue(). A scheduler may attempt to dispatch
such tasks directly to an idle CPU using the default idle selection
policy via scx_bpf_select_cpu_and() or scx_bpf_select_cpu_dfl().
This scenario must be properly handled by the built-in idle policy to
avoid returning an idle CPU where the target task isn't allowed to run.
Otherwise, it can lead to errors such as:
EXIT: runtime error (SCX_DSQ_LOCAL[_ON] cannot move migration disabled Chrome_ChildIOT[291646] from CPU 3 to 14)
Prevent this by explicitly handling migration-disabled tasks in the
built-in idle selection logic, maintaining their CPU affinity.
Fixes:
|
||
|
Christian Loehle
|
ae96bba1ca |
sched_ext: Fix scx_bpf_reenqueue_local() reference
The comment mentions bpf_scx_reenqueue_local(), but the function is provided for the BPF program implementing scx, as such the naming convention is scx_bpf_reenqueue_local(), fix the comment. Signed-off-by: Christian Loehle <christian.loehle@arm.com> Signed-off-by: Tejun Heo <tj@kernel.org> |
||
|
Breno Leitao
|
e14fd98c6d |
sched/ext: Prevent update_locked_rq() calls with NULL rq
Avoid invoking update_locked_rq() when the runqueue (rq) pointer is NULL
in the SCX_CALL_OP and SCX_CALL_OP_RET macros.
Previously, calling update_locked_rq(NULL) with preemption enabled could
trigger the following warning:
BUG: using __this_cpu_write() in preemptible [00000000]
This happens because __this_cpu_write() is unsafe to use in preemptible
context.
rq is NULL when an ops invoked from an unlocked context. In such cases, we
don't need to store any rq, since the value should already be NULL
(unlocked). Ensure that update_locked_rq() is only called when rq is
non-NULL, preventing calling __this_cpu_write() on preemptible context.
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Fixes:
|
||
|
Peter Zijlstra
|
7de9d4f946 |
sched: Start blocked_on chain processing in find_proxy_task()
Start to flesh out the real find_proxy_task() implementation, but avoid the migration cases for now, in those cases just deactivate the donor task and pick again. To ensure the donor task or other blocked tasks in the chain aren't migrated away while we're running the proxy, also tweak the fair class logic to avoid migrating donor or mutex blocked tasks. [jstultz: This change was split out from the larger proxy patch] Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Juri Lelli <juri.lelli@redhat.com> Signed-off-by: Valentin Schneider <valentin.schneider@arm.com> Signed-off-by: Connor O'Brien <connoro@google.com> Signed-off-by: John Stultz <jstultz@google.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Tested-by: K Prateek Nayak <kprateek.nayak@amd.com> Link: https://lkml.kernel.org/r/20250712033407.2383110-9-jstultz@google.com |
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|
Valentin Schneider
|
be39617e38 |
sched: Fix proxy/current (push,pull)ability
Proxy execution forms atomic pairs of tasks: The waiting donor task (scheduling context) and a proxy (execution context). The donor task, along with the rest of the blocked chain, follows the proxy wrt CPU placement. They can be the same task, in which case push/pull doesn't need any modification. When they are different, however, FIFO1 & FIFO42: ,-> RT42 | | blocked-on | v blocked_donor | mutex | | owner | v `-- RT1 RT1 RT42 CPU0 CPU1 ^ ^ | | overloaded !overloaded rq prio = 42 rq prio = 0 RT1 is eligible to be pushed to CPU1, but should that happen it will "carry" RT42 along. Clearly here neither RT1 nor RT42 must be seen as push/pullable. Unfortunately, only the donor task is usually dequeued from the rq, and the proxy'ed execution context (rq->curr) remains on the rq. This can cause RT1 to be selected for migration from logic like the rt pushable_list. Thus, adda a dequeue/enqueue cycle on the proxy task before __schedule returns, which allows the sched class logic to avoid adding the now current task to the pushable_list. Furthermore, tasks becoming blocked on a mutex don't need an explicit dequeue/enqueue cycle to be made (push/pull)able: they have to be running to block on a mutex, thus they will eventually hit put_prev_task(). Signed-off-by: Valentin Schneider <valentin.schneider@arm.com> Signed-off-by: Connor O'Brien <connoro@google.com> Signed-off-by: John Stultz <jstultz@google.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Tested-by: K Prateek Nayak <kprateek.nayak@amd.com> Link: https://lkml.kernel.org/r/20250712033407.2383110-8-jstultz@google.com |
||
|
John Stultz
|
be41bde4c3 |
sched: Add an initial sketch of the find_proxy_task() function
Add a find_proxy_task() function which doesn't do much. When we select a blocked task to run, we will just deactivate it and pick again. The exception being if it has become unblocked after find_proxy_task() was called. This allows us to validate keeping blocked tasks on the runqueue and later deactivating them is working ok, stressing the failure cases for when a proxy isn't found. Greatly simplified from patch by: Peter Zijlstra (Intel) <peterz@infradead.org> Juri Lelli <juri.lelli@redhat.com> Valentin Schneider <valentin.schneider@arm.com> Connor O'Brien <connoro@google.com> [jstultz: Split out from larger proxy patch and simplified for review and testing.] Signed-off-by: John Stultz <jstultz@google.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Tested-by: K Prateek Nayak <kprateek.nayak@amd.com> Link: https://lkml.kernel.org/r/20250712033407.2383110-7-jstultz@google.com |
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|
John Stultz
|
aa4f74dfd4 |
sched: Fix runtime accounting w/ split exec & sched contexts
Without proxy-exec, we normally charge the "current" task for both its vruntime as well as its sum_exec_runtime. With proxy, however, we have two "current" contexts: the scheduler context and the execution context. We want to charge the execution context rq->curr (ie: proxy/lock holder) execution time to its sum_exec_runtime (so it's clear to userland the rq->curr task *is* running), as well as its thread group. However the rest of the time accounting (such a vruntime and cgroup accounting), we charge against the scheduler context (rq->donor) task, because it is from that task that the time is being "donated". If the donor and curr tasks are the same, then it's the same as without proxy. Signed-off-by: John Stultz <jstultz@google.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Tested-by: K Prateek Nayak <kprateek.nayak@amd.com> Link: https://lkml.kernel.org/r/20250712033407.2383110-6-jstultz@google.com |
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|
John Stultz
|
865d8cfb16 |
sched: Move update_curr_task logic into update_curr_se
Absorb update_curr_task() into update_curr_se(), and in the process simplify update_curr_common(). This will make the next step a bit easier. Signed-off-by: John Stultz <jstultz@google.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Tested-by: K Prateek Nayak <kprateek.nayak@amd.com> Link: https://lkml.kernel.org/r/20250712033407.2383110-5-jstultz@google.com |
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|
John Stultz
|
25c411fce7 |
sched: Add CONFIG_SCHED_PROXY_EXEC & boot argument to enable/disable
Add a CONFIG_SCHED_PROXY_EXEC option, along with a boot argument sched_proxy_exec= that can be used to disable the feature at boot time if CONFIG_SCHED_PROXY_EXEC was enabled. Also uses this option to allow the rq->donor to be different from rq->curr. Signed-off-by: John Stultz <jstultz@google.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Tested-by: K Prateek Nayak <kprateek.nayak@amd.com> Link: https://lkml.kernel.org/r/20250712033407.2383110-2-jstultz@google.com |
||
|
Peter Zijlstra
|
8f2146159b |
Merge branch 'tip/sched/urgent'
Avoid merge conflicts Signed-off-by: Peter Zijlstra <peterz@infradead.org> |
||
|
K Prateek Nayak
|
1eec89a671 |
sched/topology: Remove sched_domain_topology_level::flags
Support for overlapping domains added in commit |
||
|
Li Chen
|
e075f43609 |
smpboot: introduce SDTL_INIT() helper to tidy sched topology setup
Define a small SDTL_INIT(maskfn, flagsfn, name) macro and use it to build the sched_domain_topology_level array. Purely a cleanup; behaviour is unchanged. Suggested-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Li Chen <chenl311@chinatelecom.cn> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: K Prateek Nayak <kprateek.nayak@amd.com> Tested-by: K Prateek Nayak <kprateek.nayak@amd.com> Link: https://lore.kernel.org/r/20250710105715.66594-2-me@linux.beauty |
||
|
Juri Lelli
|
440989c10f |
sched/deadline: Fix accounting after global limits change
A global limits change (sched_rt_handler() logic) currently leaves stale and/or incorrect values in variables related to accounting (e.g. extra_bw). Properly clean up per runqueue variables before implementing the change and rebuild scheduling domains (so that accounting is also properly restored) after such a change is complete. Reported-by: Marcel Ziswiler <marcel.ziswiler@codethink.co.uk> Signed-off-by: Juri Lelli <juri.lelli@redhat.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Tested-by: Marcel Ziswiler <marcel.ziswiler@codethink.co.uk> # nuc & rock5b Link: https://lore.kernel.org/r/20250627115118.438797-4-juri.lelli@redhat.com |
||
|
Juri Lelli
|
fcc9276c4d |
sched/deadline: Reset extra_bw to max_bw when clearing root domains
dl_clear_root_domain() doesn't take into account the fact that per-rq
extra_bw variables retain values computed before root domain changes,
resulting in broken accounting.
Fix it by resetting extra_bw to max_bw before restoring back dl-servers
contributions.
Fixes:
|
||
|
Juri Lelli
|
9f239df555 |
sched/deadline: Initialize dl_servers after SMP
dl-servers are currently initialized too early at boot when CPUs are not
fully up (only boot CPU is). This results in miscalculation of per
runqueue DEADLINE variables like extra_bw (which needs a stable CPU
count).
Move initialization of dl-servers later on after SMP has been
initialized and CPUs are all online, so that CPU count is stable and
DEADLINE variables can be computed correctly.
Fixes:
|
||
|
Aruna Ramakrishna
|
36569780b0 |
sched: Change nr_uninterruptible type to unsigned long
The commit |
||
|
Chen Yu
|
db6cc3f4ac |
Revert "sched/numa: add statistics of numa balance task"
This reverts commit |
||
|
Vincent Guittot
|
0b9ca2dcab |
sched/fair: Always trigger resched at the end of a protected period
Always trigger a resched after a protected period even if the entity is still eligible. It can happen that an entity remains eligible at the end of the protected period but must let an entity with a shorter slice to run in order to keep its lag shorter than slice. This is particulalry true with run to parity which tries to maximize the lag. Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20250708165630.1948751-7-vincent.guittot@linaro.org |
||
|
Vincent Guittot
|
3a0baa8e6c |
sched/fair: Fix entity's lag with run to parity
When an entity is enqueued without preempting current, we must ensure that the slice protection is updated to take into account the slice duration of the newly enqueued task so that its lag will not exceed its slice (+ tick). Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20250708165630.1948751-6-vincent.guittot@linaro.org |
||
|
Vincent Guittot
|
052c3d87c8 |
sched/fair: Limit run to parity to the min slice of enqueued entities
Run to parity ensures that current will get a chance to run its full slice in one go but this can create large latency and/or lag for entities with shorter slice that have exhausted their previous slice and wait to run their next slice. Clamp the run to parity to the shortest slice of all enqueued entities. Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20250708165630.1948751-5-vincent.guittot@linaro.org |
||
|
Vincent Guittot
|
9de74a9850 |
sched/fair: Remove spurious shorter slice preemption
Even if the waking task can preempt current, it might not be the one selected by pick_task_fair. Check that the waking task will be selected if we cancel the slice protection before doing so. Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20250708165630.1948751-4-vincent.guittot@linaro.org |
||
|
Vincent Guittot
|
74eec63661 |
sched/fair: Fix NO_RUN_TO_PARITY case
EEVDF expects the scheduler to allocate a time quantum to the selected entity and then pick a new entity for next quantum. Although this notion of time quantum is not strictly doable in our case, we can ensure a minimum runtime for each task most of the time and pick a new entity after a minimum time has elapsed. Reuse the slice protection of run to parity to ensure such runtime quantum. Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20250708165630.1948751-3-vincent.guittot@linaro.org |
||
|
Vincent Guittot
|
9cdb4fe20c |
sched/fair: Use protect_slice() instead of direct comparison
Replace the test by the relevant protect_slice() function. Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Dhaval Giani (AMD) <dhaval@gianis.ca> Link: https://lkml.kernel.org/r/20250708165630.1948751-2-vincent.guittot@linaro.org |
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Peter Zijlstra
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cccb45d7c4 |
sched/deadline: Less agressive dl_server handling
Chris reported that commit |
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Peter Zijlstra
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570c8efd5e |
sched/psi: Optimize psi_group_change() cpu_clock() usage
Dietmar reported that commit |
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Chris Mason
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155213a2ae |
sched/fair: Bump sd->max_newidle_lb_cost when newidle balance fails
schbench (https://github.com/masoncl/schbench.git) is showing a
regression from previous production kernels that bisected down to:
sched/fair: Remove sysctl_sched_migration_cost condition (
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kuyo chang
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fc975cfb36 |
sched/deadline: Fix dl_server runtime calculation formula
In our testing with 6.12 based kernel on a big.LITTLE system, we were
seeing instances of RT tasks being blocked from running on the LITTLE
cpus for multiple seconds of time, apparently by the dl_server. This
far exceeds the default configured 50ms per second runtime.
This is due to the fair dl_server runtime calculation being scaled
for frequency & capacity of the cpu.
Consider the following case under a Big.LITTLE architecture:
Assume the runtime is: 50,000,000 ns, and Frequency/capacity
scale-invariance defined as below:
Frequency scale-invariance: 100
Capacity scale-invariance: 50
First by Frequency scale-invariance,
the runtime is scaled to 50,000,000 * 100 >> 10 = 4,882,812
Then by capacity scale-invariance,
it is further scaled to 4,882,812 * 50 >> 10 = 238,418.
So it will scaled to 238,418 ns.
This smaller "accounted runtime" value is what ends up being
subtracted against the fair-server's runtime for the current period.
Thus after 50ms of real time, we've only accounted ~238us against the
fair servers runtime. This 209:1 ratio in this example means that on
the smaller cpu the fair server is allowed to continue running,
blocking RT tasks, for over 10 seconds before it exhausts its supposed
50ms of runtime. And on other hardware configurations it can be even
worse.
For the fair deadline_server, to prevent realtime tasks from being
unexpectedly delayed, we really do want to use fixed time, and not
scaled time for smaller capacity/frequency cpus. So remove the scaling
from the fair server's accounting to fix this.
Fixes:
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Peter Zijlstra
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009836b4fa |
sched/core: Fix migrate_swap() vs. hotplug
On Mon, Jun 02, 2025 at 03:22:13PM +0800, Kuyo Chang wrote:
> So, the potential race scenario is:
>
> CPU0 CPU1
> // doing migrate_swap(cpu0/cpu1)
> stop_two_cpus()
> ...
> // doing _cpu_down()
> sched_cpu_deactivate()
> set_cpu_active(cpu, false);
> balance_push_set(cpu, true);
> cpu_stop_queue_two_works
> __cpu_stop_queue_work(stopper1,...);
> __cpu_stop_queue_work(stopper2,..);
> stop_cpus_in_progress -> true
> preempt_enable();
> ...
> 1st balance_push
> stop_one_cpu_nowait
> cpu_stop_queue_work
> __cpu_stop_queue_work
> list_add_tail -> 1st add push_work
> wake_up_q(&wakeq); -> "wakeq is empty.
> This implies that the stopper is at wakeq@migrate_swap."
> preempt_disable
> wake_up_q(&wakeq);
> wake_up_process // wakeup migrate/0
> try_to_wake_up
> ttwu_queue
> ttwu_queue_cond ->meet below case
> if (cpu == smp_processor_id())
> return false;
> ttwu_do_activate
> //migrate/0 wakeup done
> wake_up_process // wakeup migrate/1
> try_to_wake_up
> ttwu_queue
> ttwu_queue_cond
> ttwu_queue_wakelist
> __ttwu_queue_wakelist
> __smp_call_single_queue
> preempt_enable();
>
> 2nd balance_push
> stop_one_cpu_nowait
> cpu_stop_queue_work
> __cpu_stop_queue_work
> list_add_tail -> 2nd add push_work, so the double list add is detected
> ...
> ...
> cpu1 get ipi, do sched_ttwu_pending, wakeup migrate/1
>
So this balance_push() is part of schedule(), and schedule() is supposed
to switch to stopper task, but because of this race condition, stopper
task is stuck in WAKING state and not actually visible to be picked.
Therefore CPU1 can do another schedule() and end up doing another
balance_push() even though the last one hasn't been done yet.
This is a confluence of fail, where both wake_q and ttwu_wakelist can
cause crucial wakeups to be delayed, resulting in the malfunction of
balance_push.
Since there is only a single stopper thread to be woken, the wake_q
doesn't really add anything here, and can be removed in favour of
direct wakeups of the stopper thread.
Then add a clause to ttwu_queue_cond() to ensure the stopper threads
are never queued / delayed.
Of all 3 moving parts, the last addition was the balance_push()
machinery, so pick that as the point the bug was introduced.
Fixes:
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Thomas Weißschuh
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3ebb1b6522 |
sched: Fix preemption string of preempt_dynamic_none
Zero is a valid value for "preempt_dynamic_mode", namely
"preempt_dynamic_none".
Fix the off-by-one in preempt_model_str(), so that "preempty_dynamic_none"
is correctly formatted as PREEMPT(none) instead of PREEMPT(undef).
Fixes:
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