The following commit has been merged into the timers/core branch of tip: Commit-ID: 6e317c32fd39a13e4854a27958d5e35d15d196be Gitweb: https://git.kernel.org/tip/6e317c32fd39a13e4854a27958d5e35d15d196be Author: Alexander Popov <alex.popov@xxxxxxxxx> AuthorDate: Sat, 18 Jan 2020 01:59:00 +03:00 Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx> CommitterDate: Mon, 17 Feb 2020 20:12:19 +01:00 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@xxxxxxxxx> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Link: https://lkml.kernel.org/r/20200117225900.16340-1-alex.popov@xxxxxxxxx --- kernel/time/timer.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-) diff --git a/kernel/time/timer.c b/kernel/time/timer.c index 4820823..cb34fac 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)
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