Commit 50f53b23 authored by Thomas Gleixner's avatar Thomas Gleixner
Browse files

posix-timers: Simplify lock/unlock_timer() 



Since the integration of sigqueue into the timer struct, lock_timer() is
only used in task context. So taking the lock with irqsave() is not longer
required.

Convert it to use spin_[un]lock_irq().

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Reviewed-by: default avatarFrederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/all/20250308155623.959825668@linutronix.de
parent a31a300c

kernel/time/posix-timers.c

+29 −41
Original line number Diff line number Diff line
@@ -53,14 +53,19 @@ static const struct k_clock clock_realtime, clock_monotonic; 
#error "SIGEV_THREAD_ID must not share bit with other SIGEV values!"

#endif



static struct k_itimer *__lock_timer(timer_t timer_id, unsigned long *flags);

static struct k_itimer *__lock_timer(timer_t timer_id);



#define lock_timer(tid, flags)						   \

#define lock_timer(tid)							\

({	struct k_itimer *__timr;					\

	__cond_lock(&__timr->it_lock, __timr = __lock_timer(tid, flags));  \

	__cond_lock(&__timr->it_lock, __timr = __lock_timer(tid));	\

	__timr;								\

})



static inline void unlock_timer(struct k_itimer *timr)

{

	spin_unlock_irq(&timr->it_lock);

}



static int hash(struct signal_struct *sig, unsigned int nr)

{

	return hash_32(hash32_ptr(sig) ^ nr, HASH_BITS(posix_timers_hashtable));
@@ -144,11 +149,6 @@ static int posix_timer_add(struct k_itimer *timer) 
	return -EAGAIN;

}



static inline void unlock_timer(struct k_itimer *timr, unsigned long flags)

{

	spin_unlock_irqrestore(&timr->it_lock, flags);

}



static int posix_get_realtime_timespec(clockid_t which_clock, struct timespec64 *tp)

{

	ktime_get_real_ts64(tp);
@@ -538,7 +538,7 @@ COMPAT_SYSCALL_DEFINE3(timer_create, clockid_t, which_clock, 
}

#endif



static struct k_itimer *__lock_timer(timer_t timer_id, unsigned long *flags)

static struct k_itimer *__lock_timer(timer_t timer_id)

{

	struct k_itimer *timr;
@@ -580,14 +580,14 @@ static struct k_itimer *__lock_timer(timer_t timer_id, unsigned long *flags) 
	guard(rcu)();

	timr = posix_timer_by_id(timer_id);

	if (timr) {

		spin_lock_irqsave(&timr->it_lock, *flags);

		spin_lock_irq(&timr->it_lock);

		/*

		 * Validate under timr::it_lock that timr::it_signal is

		 * still valid. Pairs with #1 above.

		 */

		if (timr->it_signal == current->signal)

			return timr;

		spin_unlock_irqrestore(&timr->it_lock, *flags);

		spin_unlock_irq(&timr->it_lock);

	}

	return NULL;

}
@@ -680,17 +680,16 @@ void common_timer_get(struct k_itimer *timr, struct itimerspec64 *cur_setting) 
static int do_timer_gettime(timer_t timer_id,  struct itimerspec64 *setting)

{

	struct k_itimer *timr;

	unsigned long flags;

	int ret = 0;



	timr = lock_timer(timer_id, &flags);

	timr = lock_timer(timer_id);

	if (!timr)

		return -EINVAL;



	memset(setting, 0, sizeof(*setting));

	timr->kclock->timer_get(timr, setting);



	unlock_timer(timr, flags);

	unlock_timer(timr);

	return ret;

}
@@ -746,15 +745,14 @@ SYSCALL_DEFINE2(timer_gettime32, timer_t, timer_id, 
SYSCALL_DEFINE1(timer_getoverrun, timer_t, timer_id)

{

	struct k_itimer *timr;

	unsigned long flags;

	int overrun;



	timr = lock_timer(timer_id, &flags);

	timr = lock_timer(timer_id);

	if (!timr)

		return -EINVAL;



	overrun = timer_overrun_to_int(timr);

	unlock_timer(timr, flags);

	unlock_timer(timr);



	return overrun;

}
@@ -813,14 +811,13 @@ static void common_timer_wait_running(struct k_itimer *timer) 
 * when the task which tries to delete or disarm the timer has preempted

 * the task which runs the expiry in task work context.

 */

static struct k_itimer *timer_wait_running(struct k_itimer *timer,

					   unsigned long *flags)

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 */

	scoped_guard (rcu) {

		unlock_timer(timer, *flags);

		unlock_timer(timer);

		/*

		 * kc->timer_wait_running() might drop RCU lock. So @timer

		 * cannot be touched anymore after the function returns!
@@ -829,7 +826,7 @@ static struct k_itimer *timer_wait_running(struct k_itimer *timer, 
	}



	/* Relock the timer. It might be not longer hashed. */

	return lock_timer(timer_id, flags);

	return lock_timer(timer_id);

}



/*
@@ -889,7 +886,6 @@ static int do_timer_settime(timer_t timer_id, int tmr_flags, 
			    struct itimerspec64 *old_spec64)

{

	struct k_itimer *timr;

	unsigned long flags;

	int error;



	if (!timespec64_valid(&new_spec64->it_interval) ||
@@ -899,7 +895,7 @@ static int do_timer_settime(timer_t timer_id, int tmr_flags, 
	if (old_spec64)

		memset(old_spec64, 0, sizeof(*old_spec64));



	timr = lock_timer(timer_id, &flags);

	timr = lock_timer(timer_id);

retry:

	if (!timr)

		return -EINVAL;
@@ -916,10 +912,10 @@ static int do_timer_settime(timer_t timer_id, int tmr_flags, 
		// We already got the old time...

		old_spec64 = NULL;

		/* Unlocks and relocks the timer if it still exists */

		timr = timer_wait_running(timr, &flags);

		timr = timer_wait_running(timr);

		goto retry;

	}

	unlock_timer(timr, flags);

	unlock_timer(timr);



	return error;

}
@@ -995,10 +991,7 @@ static inline void posix_timer_cleanup_ignored(struct k_itimer *tmr) 
/* Delete a POSIX.1b interval timer. */

SYSCALL_DEFINE1(timer_delete, timer_t, timer_id)

{

	struct k_itimer *timer;

	unsigned long flags;



	timer = lock_timer(timer_id, &flags);

	struct k_itimer *timer = lock_timer(timer_id);



retry_delete:

	if (!timer)
@@ -1009,7 +1002,7 @@ SYSCALL_DEFINE1(timer_delete, timer_t, timer_id) 


	if (unlikely(timer->kclock->timer_del(timer) == TIMER_RETRY)) {

		/* Unlocks and relocks the timer if it still exists */

		timer = timer_wait_running(timer, &flags);

		timer = timer_wait_running(timer);

		goto retry_delete;

	}
@@ -1028,7 +1021,7 @@ SYSCALL_DEFINE1(timer_delete, timer_t, timer_id) 
		WRITE_ONCE(timer->it_signal, NULL);

	}



	unlock_timer(timer, flags);

	unlock_timer(timer);

	posix_timer_unhash_and_free(timer);

	return 0;

}
@@ -1039,12 +1032,7 @@ SYSCALL_DEFINE1(timer_delete, timer_t, timer_id) 
 */

static void itimer_delete(struct k_itimer *timer)

{

	unsigned long flags;



	/*

	 * irqsave is required to make timer_wait_running() work.

	 */

	spin_lock_irqsave(&timer->it_lock, flags);

	spin_lock_irq(&timer->it_lock);



retry_delete:

	/*
@@ -1065,7 +1053,7 @@ static void itimer_delete(struct k_itimer *timer) 
		 * do_exit() only for the last thread of the thread group.

		 * So no other task can access and delete that timer.

		 */

		if (WARN_ON_ONCE(timer_wait_running(timer, &flags) != timer))

		if (WARN_ON_ONCE(timer_wait_running(timer) != timer))

			return;



		goto retry_delete;
@@ -1082,7 +1070,7 @@ static void itimer_delete(struct k_itimer *timer) 
	 */

	WRITE_ONCE(timer->it_signal, NULL);



	spin_unlock_irqrestore(&timer->it_lock, flags);

	spin_unlock_irq(&timer->it_lock);

	posix_timer_unhash_and_free(timer);

}