Commit-ID: f8d1b0549263354b8d8854fefc521ac536be70ff Gitweb: https://git.kernel.org/tip/f8d1b0549263354b8d8854fefc521ac536be70ff Author: Thomas Gleixner <t...@linutronix.de> AuthorDate: Wed, 31 Jul 2019 00:33:53 +0200 Committer: Thomas Gleixner <t...@linutronix.de> CommitDate: Thu, 1 Aug 2019 17:46:42 +0200
posix-timers: Rework cancel retry loops As a preparatory step for adding the PREEMPT RT specific synchronization mechanism to wait for a running timer callback, rework the timer cancel retry loops so they call a common function. This allows trivial substitution in one place. Originally-by: Anna-Maria Gleixner <anna-ma...@linutronix.de> Signed-off-by: Thomas Gleixner <t...@linutronix.de> Acked-by: Peter Zijlstra (Intel) <pet...@infradead.org> Link: https://lkml.kernel.org/r/20190730223828.874901...@linutronix.de --- kernel/time/posix-timers.c | 29 +++++++++++++++++++++++------ 1 file changed, 23 insertions(+), 6 deletions(-) diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c index f5aedd2f60df..bbe8f9686a70 100644 --- a/kernel/time/posix-timers.c +++ b/kernel/time/posix-timers.c @@ -805,6 +805,17 @@ static int common_hrtimer_try_to_cancel(struct k_itimer *timr) return hrtimer_try_to_cancel(&timr->it.real.timer); } +static struct k_itimer *timer_wait_running(struct k_itimer *timer, + unsigned long *flags) +{ + timer_t timer_id = READ_ONCE(timer->it_id); + + unlock_timer(timer, *flags); + cpu_relax(); + /* Relock the timer. It might be not longer hashed. */ + return lock_timer(timer_id, flags); +} + /* Set a POSIX.1b interval timer. */ int common_timer_set(struct k_itimer *timr, int flags, struct itimerspec64 *new_setting, @@ -859,8 +870,9 @@ static int do_timer_settime(timer_t timer_id, int tmr_flags, if (old_spec64) memset(old_spec64, 0, sizeof(*old_spec64)); -retry: + timr = lock_timer(timer_id, &flags); +retry: if (!timr) return -EINVAL; @@ -870,11 +882,14 @@ retry: else error = kc->timer_set(timr, tmr_flags, new_spec64, old_spec64); - unlock_timer(timr, flags); if (error == TIMER_RETRY) { - old_spec64 = NULL; // We already got the old time... + // We already got the old time... + old_spec64 = NULL; + /* Unlocks and relocks the timer if it still exists */ + timr = timer_wait_running(timr, &flags); goto retry; } + unlock_timer(timr, flags); return error; } @@ -951,13 +966,15 @@ SYSCALL_DEFINE1(timer_delete, timer_t, timer_id) struct k_itimer *timer; unsigned long flags; -retry_delete: timer = lock_timer(timer_id, &flags); + +retry_delete: if (!timer) return -EINVAL; - if (timer_delete_hook(timer) == TIMER_RETRY) { - unlock_timer(timer, flags); + if (unlikely(timer_delete_hook(timer) == TIMER_RETRY)) { + /* Unlocks and relocks the timer if it still exists */ + timer = timer_wait_running(timer, &flags); goto retry_delete; }
