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author | Thomas Gleixner <tglx@linutronix.de> | 2019-08-02 07:35:59 +0200 |
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committer | Thomas Gleixner <tglx@linutronix.de> | 2019-08-20 22:05:46 +0200 |
commit | ec8f954a40da8cd3d159713b608e901f0cd909a9 (patch) | |
tree | a6099be5d308424ad07e3332f45cc3b757b28e90 /kernel/time/posix-timers.c | |
parent | posix-timers: Move rcu_head out of it union (diff) | |
download | linux-ec8f954a40da8cd3d159713b608e901f0cd909a9.tar.xz linux-ec8f954a40da8cd3d159713b608e901f0cd909a9.zip |
posix-timers: Use a callback for cancel synchronization on PREEMPT_RT
Posix timer delete retry loops are affected by the same priority inversion
and live lock issues as the other timers.
Provide a RT specific synchronization function which keeps a reference to
the timer by holding rcu read lock to prevent the timer from being freed,
dropping the timer lock and invoking the timer specific wait function via a
new callback.
This does not yet cover posix CPU timers because they need more special
treatment on PREEMPT_RT.
[ This is folded into the original attempt which did not use a callback. ]
Originally-by: Anna-Maria Gleixenr <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lkml.kernel.org/r/20190819143801.656864506@linutronix.de
Diffstat (limited to 'kernel/time/posix-timers.c')
-rw-r--r-- | kernel/time/posix-timers.c | 18 |
1 files changed, 17 insertions, 1 deletions
diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c index 3e663f982c82..9e377830cc10 100644 --- a/kernel/time/posix-timers.c +++ b/kernel/time/posix-timers.c @@ -805,13 +805,25 @@ static int common_hrtimer_try_to_cancel(struct k_itimer *timr) return hrtimer_try_to_cancel(&timr->it.real.timer); } +static void common_timer_wait_running(struct k_itimer *timer) +{ + hrtimer_cancel_wait_running(&timer->it.real.timer); +} + static struct k_itimer *timer_wait_running(struct k_itimer *timer, unsigned long *flags) { + const struct k_clock *kc = READ_ONCE(timer->kclock); timer_t timer_id = READ_ONCE(timer->it_id); + /* Prevent kfree(timer) after dropping the lock */ + rcu_read_lock(); unlock_timer(timer, *flags); - cpu_relax(); + + if (!WARN_ON_ONCE(!kc->timer_wait_running)) + kc->timer_wait_running(timer); + + rcu_read_unlock(); /* Relock the timer. It might be not longer hashed. */ return lock_timer(timer_id, flags); } @@ -1255,6 +1267,7 @@ static const struct k_clock clock_realtime = { .timer_forward = common_hrtimer_forward, .timer_remaining = common_hrtimer_remaining, .timer_try_to_cancel = common_hrtimer_try_to_cancel, + .timer_wait_running = common_timer_wait_running, .timer_arm = common_hrtimer_arm, }; @@ -1270,6 +1283,7 @@ static const struct k_clock clock_monotonic = { .timer_forward = common_hrtimer_forward, .timer_remaining = common_hrtimer_remaining, .timer_try_to_cancel = common_hrtimer_try_to_cancel, + .timer_wait_running = common_timer_wait_running, .timer_arm = common_hrtimer_arm, }; @@ -1300,6 +1314,7 @@ static const struct k_clock clock_tai = { .timer_forward = common_hrtimer_forward, .timer_remaining = common_hrtimer_remaining, .timer_try_to_cancel = common_hrtimer_try_to_cancel, + .timer_wait_running = common_timer_wait_running, .timer_arm = common_hrtimer_arm, }; @@ -1315,6 +1330,7 @@ static const struct k_clock clock_boottime = { .timer_forward = common_hrtimer_forward, .timer_remaining = common_hrtimer_remaining, .timer_try_to_cancel = common_hrtimer_try_to_cancel, + .timer_wait_running = common_timer_wait_running, .timer_arm = common_hrtimer_arm, }; |