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    Subject[tip: timers/core] posix-timers: Clarify timer_wait_running() comment
    The following commit has been merged into the timers/core branch of tip:

    Commit-ID: 7d9909026645064cd31b20cee5939a0f72282261
    Gitweb: https://git.kernel.org/tip/7d9909026645064cd31b20cee5939a0f72282261
    Author: Thomas Gleixner <tglx@linutronix.de>
    AuthorDate: Tue, 25 Apr 2023 20:49:00 +02:00
    Committer: Thomas Gleixner <tglx@linutronix.de>
    CommitterDate: Sun, 18 Jun 2023 22:41:48 +02:00

    posix-timers: Clarify timer_wait_running() comment

    Explain it better and add the CONFIG_POSIX_CPU_TIMERS_TASK_WORK=y aspect
    for completeness.

    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
    Link: https://lore.kernel.org/r/20230425183312.985681995@linutronix.de

    ---
    kernel/time/posix-timers.c | 16 ++++++++++++----
    1 file changed, 12 insertions(+), 4 deletions(-)

    diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c
    index 2d6cf93..0c61f29 100644
    --- a/kernel/time/posix-timers.c
    +++ b/kernel/time/posix-timers.c
    @@ -836,10 +836,18 @@ static void common_timer_wait_running(struct k_itimer *timer)
    }

    /*
    - * On PREEMPT_RT this prevent priority inversion against softirq kthread in
    - * case it gets preempted while executing a timer callback. See comments in
    - * hrtimer_cancel_wait_running. For PREEMPT_RT=n this just results in a
    - * cpu_relax().
    + * On PREEMPT_RT this prevents priority inversion and a potential livelock
    + * against the ksoftirqd thread in case that ksoftirqd gets preempted while
    + * executing a hrtimer callback.
    + *
    + * See the comments in hrtimer_cancel_wait_running(). For PREEMPT_RT=n this
    + * just results in a cpu_relax().
    + *
    + * For POSIX CPU timers with CONFIG_POSIX_CPU_TIMERS_TASK_WORK=n this is
    + * just a cpu_relax(). With CONFIG_POSIX_CPU_TIMERS_TASK_WORK=y this
    + * prevents spinning on an eventually scheduled out task and a livelock
    + * when the task which tries to delete or disarm the timer has preempted
    + * the task which runs the expiry in task work context.
    */
    static struct k_itimer *timer_wait_running(struct k_itimer *timer,
    unsigned long *flags)
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