commit 899921025b406a71a8aeb2d7855658ea0cf0ed23
author Oleg Nesterov <oleg@tv-sign.ru> Mon Dec 01 14:18:15 2008 -0800
committer Ingo Molnar <mingo@elte.hu> Fri Dec 12 17:00:34 2008 +0100
tree 6faf12eb15231b6a430d0e1e11a4f6fcc581874e
parent 27af4245b6ce99e08c6a7c38825383bf51119cc9

posix-timers: check ->it_signal instead of ->it_pid to validate the timer

Impact: clean up, speed up

->it_pid (was ->it_process) has also a special meaning: if it is NULL,
the timer is under deletion or it wasn't initialized yet. We can check
->it_signal != NULL instead, this way we can

	- simplify sys_timer_create() a bit

	- remove yet another check from lock_timer()

	- move put_pid(->it_pid) into release_posix_timer() which
	  runs outside of ->it_lock

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

kernel/posix-timers.c

diff --git a/kernel/posix-timers.c b/kernel/posix-timers.c
index 42a39af..aa922bb 100644
--- a/kernel/posix-timers.c
+++ b/kernel/posix-timers.c
@@ -464,6 +464,7 @@
 		idr_remove(&posix_timers_id, tmr->it_id);
 		spin_unlock_irqrestore(&idr_lock, flags);
 	}
+	put_pid(tmr->it_pid);
 	sigqueue_free(tmr->sigq);
 	kmem_cache_free(posix_timers_cache, tmr);
 }
@@ -477,7 +478,6 @@
 {
 	struct k_itimer *new_timer;
 	int error, new_timer_id;
-	struct pid *it_pid;
 	sigevent_t event;
 	int it_id_set = IT_ID_NOT_SET;
 
@@ -531,9 +531,9 @@
 			goto out;
 		}
 		rcu_read_lock();
-		it_pid = get_pid(good_sigevent(&event));
+		new_timer->it_pid = get_pid(good_sigevent(&event));
 		rcu_read_unlock();
-		if (!it_pid) {
+		if (!new_timer->it_pid) {
 			error = -EINVAL;
 			goto out;
 		}
@@ -541,7 +541,7 @@
 		event.sigev_notify = SIGEV_SIGNAL;
 		event.sigev_signo = SIGALRM;
 		event.sigev_value.sival_int = new_timer->it_id;
-		it_pid = get_pid(task_tgid(current));
+		new_timer->it_pid = get_pid(task_tgid(current));
 	}
 
 	new_timer->it_sigev_notify     = event.sigev_notify;
@@ -551,7 +551,6 @@
 	new_timer->sigq->info.si_code  = SI_TIMER;
 
 	spin_lock_irq(&current->sighand->siglock);
-	new_timer->it_pid = it_pid;
 	new_timer->it_signal = current->signal;
 	list_add(&new_timer->list, &current->signal->posix_timers);
 	spin_unlock_irq(&current->sighand->siglock);
@@ -587,7 +586,7 @@
 	timr = idr_find(&posix_timers_id, (int)timer_id);
 	if (timr) {
 		spin_lock(&timr->it_lock);
-		if (timr->it_pid && timr->it_signal == current->signal) {
+		if (timr->it_signal == current->signal) {
 			spin_unlock(&idr_lock);
 			return timr;
 		}
@@ -834,8 +833,7 @@
 	 * This keeps any tasks waiting on the spin lock from thinking
 	 * they got something (see the lock code above).
 	 */
-	put_pid(timer->it_pid);
-	timer->it_pid = NULL;
+	timer->it_signal = NULL;
 
 	unlock_timer(timer, flags);
 	release_posix_timer(timer, IT_ID_SET);
@@ -861,8 +859,7 @@
 	 * This keeps any tasks waiting on the spin lock from thinking
 	 * they got something (see the lock code above).
 	 */
-	put_pid(timer->it_pid);
-	timer->it_pid = NULL;
+	timer->it_signal = NULL;
 
 	unlock_timer(timer, flags);
 	release_posix_timer(timer, IT_ID_SET);