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author | Peter Zijlstra <a.p.zijlstra@chello.nl> | 2012-03-06 17:54:26 (GMT) |
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committer | Ingo Molnar <mingo@elte.hu> | 2012-03-12 19:43:17 (GMT) |
commit | 8e3fabfde445a872c8aec2296846badf24d7c8b4 (patch) | |
tree | 60f47d850adc39aff6de56ec82d7e1a13d93d4a8 | |
parent | 3ccf3e8306156a28213adc720aba807e9a901ad5 (diff) | |
download | linux-fsl-qoriq-8e3fabfde445a872c8aec2296846badf24d7c8b4.tar.xz |
sched: Update yield() docs
Suggested-by: Joe Perches <joe@perches.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1331056466.11248.327.camel@twins
Signed-off-by: Ingo Molnar <mingo@elte.hu>
-rw-r--r-- | kernel/sched/core.c | 20 |
1 files changed, 18 insertions, 2 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 8781cec..47614a5 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -4577,8 +4577,24 @@ EXPORT_SYMBOL(__cond_resched_softirq); /** * yield - yield the current processor to other threads. * - * This is a shortcut for kernel-space yielding - it marks the - * thread runnable and calls sys_sched_yield(). + * Do not ever use this function, there's a 99% chance you're doing it wrong. + * + * The scheduler is at all times free to pick the calling task as the most + * eligible task to run, if removing the yield() call from your code breaks + * it, its already broken. + * + * Typical broken usage is: + * + * while (!event) + * yield(); + * + * where one assumes that yield() will let 'the other' process run that will + * make event true. If the current task is a SCHED_FIFO task that will never + * happen. Never use yield() as a progress guarantee!! + * + * If you want to use yield() to wait for something, use wait_event(). + * If you want to use yield() to be 'nice' for others, use cond_resched(). + * If you still want to use yield(), do not! */ void __sched yield(void) { |