Messages in this thread Patch in this message | | | From | Matthew Garrett <> | Subject | [PATCH] hrtimers: Special-case zero length sleeps | Date | Thu, 29 Sep 2011 10:59:32 -0400 |
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sleep(0) is a common construct used by applications that want to trigger the scheduler. sched_yield() might make more sense, but only appeared in POSIX.1-2001 and so plenty of example code still uses the sleep(0) form. This wouldn't normally be a problem, but it means that event-driven applications that are merely trying to avoid starving other processes may actually end up sleeping due to having large timer_slack values. Special- casing this seems reasonable.
Signed-off-by: Matthew Garrett <mjg@redhat.com> --- kernel/hrtimer.c | 8 ++++++++ 1 files changed, 8 insertions(+), 0 deletions(-)
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c index a9205e3..0bb70a7 100644 --- a/kernel/hrtimer.c +++ b/kernel/hrtimer.c @@ -1566,6 +1566,14 @@ long hrtimer_nanosleep(struct timespec *rqtp, struct timespec __user *rmtp, if (rt_task(current)) slack = 0; + /* + * Applications will often sleep(0) to indicate that they wish to + * be scheduled. Special case that to avoid actually putting them + * to sleep for the duration of the slack. + */ + if (rqtp->tv_sec == 0 && rqtp->tv_nsec == 0) + slack = 0; + hrtimer_init_on_stack(&t.timer, clockid, mode); hrtimer_set_expires_range_ns(&t.timer, timespec_to_ktime(*rqtp), slack); if (do_nanosleep(&t, mode)) -- 1.7.6.4
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