Paul E. McKenney dd56af42bd rcu: Eliminate deadlock between CPU hotplug and expedited grace periods ... Currently, the expedited grace-period primitives do get_online_cpus(). This greatly simplifies their implementation, but means that calls to them holding locks that are acquired by CPU-hotplug notifiers (to say nothing of calls to these primitives from CPU-hotplug notifiers) can deadlock. But this is starting to become inconvenient, as can be seen here: https://lkml.org/lkml/2014/8/5/754. The problem in this case is that some developers need to acquire a mutex from a CPU-hotplug notifier, but also need to hold it across a synchronize_rcu_expedited(). As noted above, this currently results in deadlock. This commit avoids the deadlock and retains the simplicity by creating a try_get_online_cpus(), which returns false if the get_online_cpus() reference count could not immediately be incremented. If a call to try_get_online_cpus() returns true, the expedited primitives operate as before. If a call returns false, the expedited primitives fall back to normal grace-period operations. This falling back of course results in increased grace-period latency, but only during times when CPU hotplug operations are actually in flight. The effect should therefore be negligible during normal operation. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Josh Triplett <josh@joshtriplett.org> Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net> Tested-by: Lan Tianyu <tianyu.lan@intel.com>		2014-09-18 16:22:27 -07:00
..
bpf	net: filter: split 'struct sk_filter' into socket and bpf parts	2014-08-02 15:03:58 -07:00
debug	kdb: Use ktime_get_ts()	2014-06-12 16:18:45 +02:00
events	Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2014-08-24 16:16:55 -07:00
gcov	kernel/gcov/fs.c: remove unnecessary null test before debugfs_remove	2014-08-08 15:57:24 -07:00
irq	Merge branch 'irq-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2014-08-05 17:38:45 -07:00
locking	locktorture: Introduce torture context	2014-09-16 13:41:40 -07:00
power	Merge branches 'pm-sleep', 'pm-cpufreq' and 'pm-cpuidle'	2014-08-11 23:19:48 +02:00
printk	printk: Add function to return log buffer address and size	2014-08-13 15:13:44 +10:00
rcu	rcu: Eliminate deadlock between CPU hotplug and expedited grace periods	2014-09-18 16:22:27 -07:00
sched	Merge branches 'pm-sleep', 'pm-cpufreq' and 'pm-cpuidle'	2014-08-11 23:19:48 +02:00
time	timekeeping: Another fix to the VSYSCALL_OLD update_vsyscall	2014-08-14 11:04:11 -06:00
trace	ftrace: Use current addr when converting to nop in __ftrace_replace_code()	2014-08-22 21:04:35 -04:00
.gitignore
acct.c	kernel/acct.c: fix coding style warnings and errors	2014-08-08 15:57:27 -07:00
async.c
audit.c	CAPABILITIES: remove undefined caps from all processes	2014-07-24 21:53:47 +10:00
audit.h
audit_tree.c
audit_watch.c
auditfilter.c	kernel/auditfilter.c: replace count*size kmalloc by kcalloc	2014-08-06 18:01:12 -07:00
auditsc.c	auditsc: audit_krule mask accesses need bounds checking	2014-06-10 08:44:40 -07:00
backtracetest.c	kernel/backtracetest.c: replace no level printk by pr_info()	2014-06-04 16:54:14 -07:00
bounds.c	page-cgroup: get rid of NR_PCG_FLAGS	2014-08-08 15:57:18 -07:00
capability.c	CAPABILITIES: remove undefined caps from all processes	2014-07-24 21:53:47 +10:00
cgroup.c	Merge branch 'for-3.17' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup	2014-08-04 10:11:28 -07:00
cgroup_freezer.c	cgroup: rename cgroup_subsys->base_cftypes to ->legacy_cftypes	2014-07-15 11:05:09 -04:00
compat.c	kernel/compat.c: use sizeof() instead of sizeof	2014-06-04 16:54:19 -07:00
configs.c
context_tracking.c	x86/kprobes: Fix build errors and blacklist context_track_user	2014-06-14 09:07:44 +02:00
cpu.c	rcu: Eliminate deadlock between CPU hotplug and expedited grace periods	2014-09-18 16:22:27 -07:00
cpu_pm.c
cpuset.c	Merge branch 'for-3.17' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup	2014-08-04 10:11:28 -07:00
crash_dump.c
cred.c
delayacct.c	delayacct: Remove braindamaged type conversions	2014-07-23 10:18:06 -07:00
dma.c
elfcore.c
exec_domain.c	kernel/exec_domain.c: code clean-up	2014-06-04 16:54:15 -07:00
exit.c	rcu: Make TASKS_RCU handle tasks that are almost done exiting	2014-09-07 16:27:22 -07:00
extable.c
fork.c	seccomp: Replace BUG(!spin_is_locked()) with assert_spin_lock	2014-08-11 13:29:12 -07:00
freezer.c
futex.c	futex: Simplify futex_lock_pi_atomic() and make it more robust	2014-06-21 22:26:24 +02:00
futex_compat.c
groups.c
hung_task.c	kernel/hung_task.c: convert simple_strtoul to kstrtouint	2014-06-04 16:54:15 -07:00
irq_work.c	irq_work: Remove BUG_ON in irq_work_run()	2014-07-05 11:17:26 +02:00
jump_label.c
kallsyms.c	kernel/kallsyms.c: fix %pB when there's no symbol at the address	2014-08-08 15:57:18 -07:00
kcmp.c
Kconfig.freezer
Kconfig.hz
Kconfig.locks	locking/rwsem: Add CONFIG_RWSEM_SPIN_ON_OWNER	2014-07-16 14:57:13 +02:00
Kconfig.preempt
kexec.c	kexec: verify the signature of signed PE bzImage	2014-08-08 15:57:33 -07:00
kmod.c	signals: change wait_for_helper() to use kernel_sigaction()	2014-06-06 16:08:12 -07:00
kprobes.c	kprobes: Skip kretprobe hit in NMI context to avoid deadlock	2014-08-08 10:38:04 +02:00
ksysfs.c	kobject: Make support for uevent_helper optional.	2014-04-25 12:00:49 -07:00
kthread.c	kthread_work: wake up worker only when the worker is idle	2014-07-28 14:07:52 -04:00
latencytop.c	kernel/latencytop.c: convert seq_printf to seq_puts	2014-06-04 16:54:15 -07:00
Makefile	bin2c: move bin2c in scripts/basic	2014-08-08 15:57:32 -07:00
module-internal.h
module.c	module: Clean up ro/nx after early module load failures	2014-08-16 04:47:00 +09:30
module_signing.c
notifier.c	kprobes, notifier: Use NOKPROBE_SYMBOL macro in notifier	2014-04-24 10:26:39 +02:00
nsproxy.c	namespaces: Use task_lock and not rcu to protect nsproxy	2014-07-29 18:08:50 -07:00
padata.c
panic.c	panic: add TAINT_SOFTLOCKUP	2014-08-08 15:57:24 -07:00
params.c	Add module param type 'ullong'	2014-07-17 22:07:37 +02:00
pid.c
pid_namespace.c
profile.c	kernel/profile.c: use static const char instead of static char	2014-06-06 16:08:13 -07:00
ptrace.c	sched: Remove proliferation of wait_on_bit() action functions	2014-07-16 15:10:39 +02:00
range.c
reboot.c	kernel/reboot.c: convert simple_strtoul to kstrtoint	2014-06-04 16:54:15 -07:00
relay.c
res_counter.c	kernel/res_counter.c: replace simple_strtoull by kstrtoull	2014-06-04 16:54:15 -07:00
resource.c	resource: provide new functions to walk through resources	2014-08-08 15:57:32 -07:00
seccomp.c	seccomp: Replace BUG(!spin_is_locked()) with assert_spin_lock	2014-08-11 13:29:12 -07:00
signal.c	Merge branch 'signal-cleanup' of git://git.kernel.org/pub/scm/linux/kernel/git/rw/misc	2014-08-09 09:58:12 -07:00
smp.c	kernel/smp.c:on_each_cpu_cond(): fix warning in fallback path	2014-08-06 18:01:22 -07:00
smpboot.c
smpboot.h
softirq.c	rcu: Per-CPU operation cleanups to rcu_*_qs() functions	2014-09-07 16:27:35 -07:00
stacktrace.c
stop_machine.c	kernel/stop_machine.c: kernel-doc warning fix	2014-06-04 16:54:15 -07:00
sys.c	sched: move no_new_privs into new atomic flags	2014-07-18 12:13:38 -07:00
sys_ni.c	kexec: new syscall kexec_file_load() declaration	2014-08-08 15:57:32 -07:00
sysctl.c	rcutorture: Rename rcutorture_runnable parameter	2014-09-16 13:41:44 -07:00
sysctl_binary.c	ipv6: Allow accepting RA from local IP addresses.	2014-07-01 12:16:24 -07:00
system_certificates.S
system_keyring.c	KEYS: validate certificate trust only with builtin keys	2014-07-17 09:35:17 -04:00
task_work.c
taskstats.c
test_kprobes.c	kernel/test_kprobes.c: use current logging functions	2014-08-08 15:57:18 -07:00
torture.c	torture: Address race in module cleanup	2014-09-16 13:41:06 -07:00
tracepoint.c	tracing: syscall_regfunc() should not skip kernel threads	2014-06-21 00:15:26 -04:00
tsacct.c	sched: Make task->start_time nanoseconds based	2014-07-23 10:18:05 -07:00
uid16.c
up.c
user-return-notifier.c
user.c	kernel/user.c: drop unused field 'files' from user_struct	2014-06-04 16:54:16 -07:00
user_namespace.c	proc: constify seq_operations	2014-08-08 15:57:22 -07:00
utsname.c	namespaces: Use task_lock and not rcu to protect nsproxy	2014-07-29 18:08:50 -07:00
utsname_sysctl.c	sysctl: convert use of typedef ctl_table to struct ctl_table	2014-06-06 16:08:16 -07:00
watchdog.c	panic: add TAINT_SOFTLOCKUP	2014-08-08 15:57:24 -07:00
workqueue.c	Merge branch 'for-3.17' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu	2014-08-04 10:09:27 -07:00
workqueue_internal.h	workqueue: rename manager_mutex to attach_mutex	2014-05-20 10:59:32 -04:00