On Tue, 2012-03-06 at 18:54 +0100, Peter Zijlstra wrote: > On Tue, 2012-03-06 at 09:41 -0800, Joe Perches wrote: > > Perhaps the kernel-doc comments in sched/core.c > > should/could be expanded/updated. > > Something like this? > > --- > 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 2963fbb..a05a0f7 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! > */ Yes. I'll update the checkpatch message to say something like: "Using yield() is generally wrong. See yield() kernel-doc (sched/core.c)" -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>