[RFC] posix-timers: RCU conversion

Commit Message

Eric Dumazet March 21, 2011, 10:27 p.m. UTC

None

Patch

diff --git a/include/linux/posix-timers.h b/include/linux/posix-timers.h
index d51243a..5dc27ca 100644
--- a/include/linux/posix-timers.h
+++ b/include/linux/posix-timers.h
@@ -81,6 +81,7 @@  struct k_itimer {
 			unsigned long expires;
 		} mmtimer;
 	} it;
+	struct rcu_head rcu;
 };
 
 struct k_clock {
diff --git a/kernel/posix-timers.c b/kernel/posix-timers.c
index 4c01249..e2a823a 100644
--- a/kernel/posix-timers.c
+++ b/kernel/posix-timers.c
@@ -491,6 +491,11 @@  static struct k_itimer * alloc_posix_timer(void)
 	return tmr;
 }
 
+static void k_itimer_rcu_free(struct rcu_head *head)
+{
+	kmem_cache_free(posix_timers_cache, container_of(head, struct k_itimer, rcu));
+}
+
 #define IT_ID_SET	1
 #define IT_ID_NOT_SET	0
 static void release_posix_timer(struct k_itimer *tmr, int it_id_set)
@@ -499,11 +504,12 @@  static void release_posix_timer(struct k_itimer *tmr, int it_id_set)
 		unsigned long flags;
 		spin_lock_irqsave(&idr_lock, flags);
 		idr_remove(&posix_timers_id, tmr->it_id);
+		tmr->it_id = -1;
 		spin_unlock_irqrestore(&idr_lock, flags);
 	}
 	put_pid(tmr->it_pid);
 	sigqueue_free(tmr->sigq);
-	kmem_cache_free(posix_timers_cache, tmr);
+	call_rcu(&tmr->rcu, k_itimer_rcu_free);
 }
 
 static struct k_clock *clockid_to_kclock(const clockid_t id)
@@ -631,22 +637,18 @@  out:
 static struct k_itimer *__lock_timer(timer_t timer_id, unsigned long *flags)
 {
 	struct k_itimer *timr;
-	/*
-	 * Watch out here.  We do a irqsave on the idr_lock and pass the
-	 * flags part over to the timer lock.  Must not let interrupts in
-	 * while we are moving the lock.
-	 */
-	spin_lock_irqsave(&idr_lock, *flags);
+
+	rcu_read_lock();
 	timr = idr_find(&posix_timers_id, (int)timer_id);
 	if (timr) {
-		spin_lock(&timr->it_lock);
-		if (timr->it_signal == current->signal) {
-			spin_unlock(&idr_lock);
+		spin_lock_irqsave(&timr->it_lock, *flags);
+		if (timr->it_id == (int)timer_id && timr->it_signal == current->signal) {
+			rcu_read_unlock();
 			return timr;
 		}
-		spin_unlock(&timr->it_lock);
+		spin_unlock_irqrestore(&timr->it_lock, *flags);
 	}
-	spin_unlock_irqrestore(&idr_lock, *flags);
+	rcu_read_unlock();
 
 	return NULL;
 }