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printk/sched: Introduce special printk_sched() for those awkward moments

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There's a few awkward printk()s inside of scheduler guts that people
prefer to keep but really are rather deadlock prone. Fudge around it
by storing the text in a per-cpu buffer and poll it using the existing
printk_tick() handler.

This will drop output when its more frequent than once a tick, however
only the affinity thing could possible go that fast and for that just
one should suffice to notify the admin he's done something silly..

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/n/tip-wua3lmkt3dg8nfts66o6brne@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra 2012-02-27 10:47:00 +01:00 • committed by Ingo Molnar
parent 554cecaf73
commit 3ccf3e8306
4 changed files with 55 additions and 5 deletions
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10
include/linux/printk.h
View file

@ -100,6 +100,11 @@ int vprintk(const char *fmt, va_list args);
asmlinkage __printf(1, 2) __cold
int printk(const char *fmt, ...);
/*
* Special printk facility for scheduler use only, _DO_NOT_USE_ !
*/
__printf(1, 2) __cold int printk_sched(const char *fmt, ...);
/*
* Please don't use printk_ratelimit(), because it shares ratelimiting state
* with all other unrelated printk_ratelimit() callsites. Instead use
@ -127,6 +132,11 @@ int printk(const char *s, ...)
{
return 0;
}
static inline __printf(1, 2) __cold
int printk_sched(const char *s, ...)
{
return 0;
}
static inline int printk_ratelimit(void)
{
return 0;