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posix-timers: Use guards in a few places

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Switch locking and RCU to guards where applicable.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/all/20250308155623.892762130@linutronix.de
This commit is contained in:
Thomas Gleixner
2025-03-13 12:07:17 +01:00
parent f6d0c3d2eb
commit a31a300c4d
1 changed files with 30 additions and 38 deletions
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kernel/time/posix-timers.c
+30 -38
View File
@@ -397,9 +397,8 @@ void posixtimer_free_timer(struct k_itimer *tmr)
static void posix_timer_unhash_and_free(struct k_itimer *tmr)
{
spin_lock(&hash_lock);
hlist_del_rcu(&tmr->t_hash);
spin_unlock(&hash_lock);
scoped_guard (spinlock, &hash_lock)
hlist_del_rcu(&tmr->t_hash);
posixtimer_putref(tmr);
}
@@ -443,9 +442,8 @@ static int do_timer_create(clockid_t which_clock, struct sigevent *event,
new_timer->it_overrun = -1LL;
if (event) {
rcu_read_lock();
new_timer->it_pid = get_pid(good_sigevent(event));
rcu_read_unlock();
scoped_guard (rcu)
new_timer->it_pid = get_pid(good_sigevent(event));
if (!new_timer->it_pid) {
error = -EINVAL;
goto out;
@@ -579,7 +577,7 @@ static struct k_itimer *__lock_timer(timer_t timer_id, unsigned long *flags)
* can't change, but timr::it_signal becomes NULL during
* destruction.
*/
rcu_read_lock();
guard(rcu)();
timr = posix_timer_by_id(timer_id);
if (timr) {
spin_lock_irqsave(&timr->it_lock, *flags);
@@ -587,14 +585,10 @@ static struct k_itimer *__lock_timer(timer_t timer_id, unsigned long *flags)
* Validate under timr::it_lock that timr::it_signal is
* still valid. Pairs with #1 above.
*/
if (timr->it_signal == current->signal) {
rcu_read_unlock();
if (timr->it_signal == current->signal)
return timr;
}
spin_unlock_irqrestore(&timr->it_lock, *flags);
}
rcu_read_unlock();
return NULL;
}
@@ -825,16 +819,15 @@ static struct k_itimer *timer_wait_running(struct k_itimer *timer,
timer_t timer_id = READ_ONCE(timer->it_id);
/* Prevent kfree(timer) after dropping the lock */
rcu_read_lock();
unlock_timer(timer, *flags);
scoped_guard (rcu) {
unlock_timer(timer, *flags);
/*
* kc->timer_wait_running() might drop RCU lock. So @timer
* cannot be touched anymore after the function returns!
*/
timer->kclock->timer_wait_running(timer);
}
/*
* kc->timer_wait_running() might drop RCU lock. So @timer
* cannot be touched anymore after the function returns!
*/
timer->kclock->timer_wait_running(timer);
rcu_read_unlock();
/* Relock the timer. It might be not longer hashed. */
return lock_timer(timer_id, flags);
}
@@ -1020,20 +1013,20 @@ retry_delete:
goto retry_delete;
}
spin_lock(&current->sighand->siglock);
hlist_del(&timer->list);
posix_timer_cleanup_ignored(timer);
/*
* A concurrent lookup could check timer::it_signal lockless. It
* will reevaluate with timer::it_lock held and observe the NULL.
*
* It must be written with siglock held so that the signal code
* observes timer->it_signal == NULL in do_sigaction(SIG_IGN),
* which prevents it from moving a pending signal of a deleted
* timer to the ignore list.
*/
WRITE_ONCE(timer->it_signal, NULL);
spin_unlock(&current->sighand->siglock);
scoped_guard (spinlock, &current->sighand->siglock) {
hlist_del(&timer->list);
posix_timer_cleanup_ignored(timer);
/*
* A concurrent lookup could check timer::it_signal lockless. It
* will reevaluate with timer::it_lock held and observe the NULL.
*
* It must be written with siglock held so that the signal code
* observes timer->it_signal == NULL in do_sigaction(SIG_IGN),
* which prevents it from moving a pending signal of a deleted
* timer to the ignore list.
*/
WRITE_ONCE(timer->it_signal, NULL);
}
unlock_timer(timer, flags);
posix_timer_unhash_and_free(timer);
@@ -1106,9 +1099,8 @@ void exit_itimers(struct task_struct *tsk)
return;
/* Protect against concurrent read via /proc/$PID/timers */
spin_lock_irq(&tsk->sighand->siglock);
hlist_move_list(&tsk->signal->posix_timers, &timers);
spin_unlock_irq(&tsk->sighand->siglock);
scoped_guard (spinlock_irq, &tsk->sighand->siglock)
hlist_move_list(&tsk->signal->posix_timers, &timers);
/* The timers are not longer accessible via tsk::signal */
while (!hlist_empty(&timers)) {