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author | Alexander Popov <alex.popov@linux.com> | 2020-01-18 01:59:00 +0300 |
---|---|---|
committer | Thomas Gleixner <tglx@linutronix.de> | 2020-02-17 22:12:19 +0300 |
commit | 6e317c32fd39a13e4854a27958d5e35d15d196be (patch) | |
tree | 6c6170fd0ffa3b340c01085761d48be10eb4f5d1 /kernel/time | |
parent | e876f0b69dc993e86ca7795e63e98385aa9a7ef3 (diff) | |
download | linux-6e317c32fd39a13e4854a27958d5e35d15d196be.tar.xz |
timer: Improve the comment describing schedule_timeout()
When working commit 6dcd5d7a7a29c1e, a mistake was noticed by Linus:
schedule_timeout() was called without setting the task state to anything
particular.
It calls the scheduler, but doesn't delay anything, because the task stays
runnable. That happens because sched_submit_work() does nothing for tasks
in TASK_RUNNING state.
That turned out to be the intended behavior. Adding a WARN() is not useful
as the task could be woken up right after setting the state and before
reaching schedule_timeout().
Improve the comment about schedule_timeout() and describe that more
explicitly.
Signed-off-by: Alexander Popov <alex.popov@linux.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20200117225900.16340-1-alex.popov@linux.com
Diffstat (limited to 'kernel/time')
-rw-r--r-- | kernel/time/timer.c | 16 |
1 files changed, 9 insertions, 7 deletions
diff --git a/kernel/time/timer.c b/kernel/time/timer.c index 4820823515e9..cb34fac9d9f7 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -1828,21 +1828,23 @@ static void process_timeout(struct timer_list *t) * schedule_timeout - sleep until timeout * @timeout: timeout value in jiffies * - * Make the current task sleep until @timeout jiffies have - * elapsed. The routine will return immediately unless - * the current task state has been set (see set_current_state()). + * Make the current task sleep until @timeout jiffies have elapsed. + * The function behavior depends on the current task state + * (see also set_current_state() description): * - * You can set the task state as follows - + * %TASK_RUNNING - the scheduler is called, but the task does not sleep + * at all. That happens because sched_submit_work() does nothing for + * tasks in %TASK_RUNNING state. * * %TASK_UNINTERRUPTIBLE - at least @timeout jiffies are guaranteed to * pass before the routine returns unless the current task is explicitly - * woken up, (e.g. by wake_up_process())". + * woken up, (e.g. by wake_up_process()). * * %TASK_INTERRUPTIBLE - the routine may return early if a signal is * delivered to the current task or the current task is explicitly woken * up. * - * The current task state is guaranteed to be TASK_RUNNING when this + * The current task state is guaranteed to be %TASK_RUNNING when this * routine returns. * * Specifying a @timeout value of %MAX_SCHEDULE_TIMEOUT will schedule @@ -1850,7 +1852,7 @@ static void process_timeout(struct timer_list *t) * value will be %MAX_SCHEDULE_TIMEOUT. * * Returns 0 when the timer has expired otherwise the remaining time in - * jiffies will be returned. In all cases the return value is guaranteed + * jiffies will be returned. In all cases the return value is guaranteed * to be non-negative. */ signed long __sched schedule_timeout(signed long timeout) |