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posix-timers: Document sys_clock_getoverrun()

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Document the syscall in detail and with coherent sentences.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/20230425183313.462051641@linutronix.de
This commit is contained in:
Thomas Gleixner 2023-04-25 20:49:14 +02:00
parent a86e928433
commit 65cade468d
1 changed files with 17 additions and 8 deletions
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25
kernel/time/posix-timers.c
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@ -783,14 +783,23 @@ SYSCALL_DEFINE2(timer_gettime32, timer_t, timer_id,
#endif
/*
* Get the number of overruns of a POSIX.1b interval timer. This is to
* be the overrun of the timer last delivered. At the same time we are
* accumulating overruns on the next timer. The overrun is frozen when
* the signal is delivered, either at the notify time (if the info block
* is not queued) or at the actual delivery time (as we are informed by
* the call back to posixtimer_rearm(). So all we need to do is
* to pick up the frozen overrun.
/**
* sys_timer_getoverrun - Get the number of overruns of a POSIX.1b interval timer
* @timer_id: The timer ID which identifies the timer
*
* The "overrun count" of a timer is one plus the number of expiration
* intervals which have elapsed between the first expiry, which queues the
* signal and the actual signal delivery. On signal delivery the "overrun
* count" is calculated and cached, so it can be returned directly here.
*
* As this is relative to the last queued signal the returned overrun count
* is meaningless outside of the signal delivery path and even there it
* does not accurately reflect the current state when user space evaluates
* it.
*
* Returns:
* -EINVAL @timer_id is invalid
* 1..INT_MAX The number of overruns related to the last delivered signal
*/
SYSCALL_DEFINE1(timer_getoverrun, timer_t, timer_id)
{