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sched/debug: Fix 'schedstats=enable' cmdline option

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The 'schedstats=enable' option doesn't work, and also produces the
following warning during boot:

  WARNING: CPU: 0 PID: 0 at /home/jpoimboe/git/linux/kernel/jump_label.c:61 static_key_slow_inc+0x8c/0xa0
  static_key_slow_inc used before call to jump_label_init
  Modules linked in:
  CPU: 0 PID: 0 Comm: swapper Not tainted 4.7.0-rc1+ #25
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.8.1-20150318_183358- 04/01/2014
   0000000000000086 3ae3475a4bea95d4 ffffffff81e03da8 ffffffff8143fc83
   ffffffff81e03df8 0000000000000000 ffffffff81e03de8 ffffffff810b1ffb
   0000003d00000096 ffffffff823514d0 ffff88007ff197c8 0000000000000000
  Call Trace:
   [<ffffffff8143fc83>] dump_stack+0x85/0xc2
   [<ffffffff810b1ffb>] __warn+0xcb/0xf0
   [<ffffffff810b207f>] warn_slowpath_fmt+0x5f/0x80
   [<ffffffff811e9c0c>] static_key_slow_inc+0x8c/0xa0
   [<ffffffff810e07c6>] static_key_enable+0x16/0x40
   [<ffffffff8216d633>] setup_schedstats+0x29/0x94
   [<ffffffff82148a05>] unknown_bootoption+0x89/0x191
   [<ffffffff810d8617>] parse_args+0x297/0x4b0
   [<ffffffff82148d61>] start_kernel+0x1d8/0x4a9
   [<ffffffff8214897c>] ? set_init_arg+0x55/0x55
   [<ffffffff82148120>] ? early_idt_handler_array+0x120/0x120
   [<ffffffff821482db>] x86_64_start_reservations+0x2f/0x31
   [<ffffffff82148427>] x86_64_start_kernel+0x14a/0x16d

The problem is that it tries to update the 'sched_schedstats' static key
before jump labels have been initialized.

Changing jump_label_init() to be called earlier before
parse_early_param() wouldn't fix it: it would still fail trying to
poke_text() because mm isn't yet initialized.

Instead, just create a temporary '__sched_schedstats' variable which can
be copied to the static key later during sched_init() after jump labels
have been initialized.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: cb2517653f ("sched/debug: Make schedstats a runtime tunable that is disabled by default")
Link: http://lkml.kernel.org/r/453775fe3433bed65731a583e228ccea806d18cd.1465322027.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Josh Poimboeuf 2016-06-07 14:43:16 -05:00 committed by Ingo Molnar
parent 9c57259117
commit 4698f88c06
1 changed files with 22 additions and 6 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

28
kernel/sched/core.c
View file

@ -2253,9 +2253,11 @@ int sysctl_numa_balancing(struct ctl_table *table, int write,
#endif #endif
#endif #endif
DEFINE_STATIC_KEY_FALSE(sched_schedstats);
#ifdef CONFIG_SCHEDSTATS #ifdef CONFIG_SCHEDSTATS
DEFINE_STATIC_KEY_FALSE(sched_schedstats);
static bool __initdata __sched_schedstats = false;
static void set_schedstats(bool enabled) static void set_schedstats(bool enabled)
{ {
if (enabled) if (enabled)
@ -2278,11 +2280,16 @@ static int __init setup_schedstats(char *str)
if (!str) if (!str)
goto out; goto out;
/*
* This code is called before jump labels have been set up, so we can't
* change the static branch directly just yet. Instead set a temporary
* variable so init_schedstats() can do it later.
*/
if (!strcmp(str, "enable")) { if (!strcmp(str, "enable")) {
set_schedstats(true); __sched_schedstats = true;
ret = 1; ret = 1;
} else if (!strcmp(str, "disable")) { } else if (!strcmp(str, "disable")) {
set_schedstats(false); __sched_schedstats = false;
ret = 1; ret = 1;
} }
out: out:
@ -2293,6 +2300,11 @@ static int __init setup_schedstats(char *str)
} }
__setup("schedstats=", setup_schedstats); __setup("schedstats=", setup_schedstats);
static void __init init_schedstats(void)
{
set_schedstats(__sched_schedstats);
}
#ifdef CONFIG_PROC_SYSCTL #ifdef CONFIG_PROC_SYSCTL
int sysctl_schedstats(struct ctl_table *table, int write, int sysctl_schedstats(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp, loff_t *ppos) void __user *buffer, size_t *lenp, loff_t *ppos)
@ -2313,8 +2325,10 @@ int sysctl_schedstats(struct ctl_table *table, int write,
set_schedstats(state); set_schedstats(state);
return err; return err;
} }
#endif #endif /* CONFIG_PROC_SYSCTL */
#endif #else /* !CONFIG_SCHEDSTATS */
static inline void init_schedstats(void) {}
#endif /* CONFIG_SCHEDSTATS */
/* /*
* fork()/clone()-time setup: * fork()/clone()-time setup:
@ -7487,6 +7501,8 @@ void __init sched_init(void)
#endif #endif
init_sched_fair_class(); init_sched_fair_class();
init_schedstats();
scheduler_running = 1; scheduler_running = 1;
} }