Commit-ID: 8e3fabfde445a872c8aec2296846badf24d7c8b4 Gitweb: http://git.kernel.org/tip/8e3fabfde445a872c8aec2296846badf24d7c8b4 Author: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> AuthorDate: Tue, 6 Mar 2012 18:54:26 +0100 Committer: Ingo Molnar <mingo@xxxxxxx> CommitDate: Mon, 12 Mar 2012 20:43:17 +0100 sched: Update yield() docs Suggested-by: Joe Perches <joe@xxxxxxxxxxx> Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> Link: http://lkml.kernel.org/r/1331056466.11248.327.camel@twins Signed-off-by: Ingo Molnar <mingo@xxxxxxx> --- 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) { -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html