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posix-timers: Annotate concurrent access to k_itimer:: It_signal

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k_itimer::it_signal is read lockless in the RCU protected hash lookup, but
it can be written concurrently in the timer_create() and timer_delete()
path. Annotate these places with READ_ONCE() and WRITE_ONCE()

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/20230425183313.143596887@linutronix.de
This commit is contained in:
Thomas Gleixner 2023-04-25 20:49:05 +02:00
parent ae88967d71
commit 028cf5eaa1
1 changed files with 7 additions and 7 deletions
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14
kernel/time/posix-timers.c
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@ -109,9 +109,9 @@ static struct k_itimer *__posix_timers_find(struct hlist_head *head,
{
struct k_itimer *timer;
hlist_for_each_entry_rcu(timer, head, t_hash,
lockdep_is_held(&hash_lock)) {
if ((timer->it_signal == sig) && (timer->it_id == id))
hlist_for_each_entry_rcu(timer, head, t_hash, lockdep_is_held(&hash_lock)) {
/* timer->it_signal can be set concurrently */
if ((READ_ONCE(timer->it_signal) == sig) && (timer->it_id == id))
return timer;
}
return NULL;
@ -558,7 +558,7 @@ static int do_timer_create(clockid_t which_clock, struct sigevent *event,
spin_lock_irq(&current->sighand->siglock);
/* This makes the timer valid in the hash table */
new_timer->it_signal = current->signal;
WRITE_ONCE(new_timer->it_signal, current->signal);
list_add(&new_timer->list, &current->signal->posix_timers);
spin_unlock_irq(&current->sighand->siglock);
@ -1052,10 +1052,10 @@ SYSCALL_DEFINE1(timer_delete, timer_t, timer_id)
list_del(&timer->list);
spin_unlock(&current->sighand->siglock);
/*
* This keeps any tasks waiting on the spin lock from thinking
* they got something (see the lock code above).
* A concurrent lookup could check timer::it_signal lockless. It
* will reevaluate with timer::it_lock held and observe the NULL.
*/
timer->it_signal = NULL;
WRITE_ONCE(timer->it_signal, NULL);
unlock_timer(timer, flags);
release_posix_timer(timer, IT_ID_SET);