posix-timers: Small cleanup in itimer_delete()

posix-timers: Small cleanup in itimer_delete()

[Sebastian Andrzej Siewior]

Small cleanup / optimisation / clarification in itimer_delete() which I
noticed while doing other things…

Sebastian

[PATCH 1/2] posix-timers: Remove "it_signal = NULL" assignment in itimer_delete()

[Sebastian Andrzej Siewior]

itimer_delete() is invoked during do_exit(). At this point it is the
last thread in the group dying and doing the clean up.
Since it is the last thread in the group, there can not be any other
task attempting to lock the itimer which means the NULL assignment (which
avoids lookups in __lock_timer()) is not required.

The assignment and comment was copied in commit 0e568881178ff ("[PATCH]
fix posix-timers to have proper per-process scope") from
sys_timer_delete() which was/is the syscall interface and requires the
assignment.

Remove the superfluous ->it_signal = NULL assignment.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 kernel/time/posix-timers.c | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c
index 29176635991f0..caa63e58e3d88 100644
--- a/kernel/time/posix-timers.c
+++ b/kernel/time/posix-timers.c
@@ -990,11 +990,6 @@ static void itimer_delete(struct k_itimer *timer)
 		goto retry_delete;
 	}
 	list_del(&timer->list);
-	/*
-	 * This keeps any tasks waiting on the spin lock from thinking
-	 * they got something (see the lock code above).
-	 */
-	timer->it_signal = NULL;
 
 	unlock_timer(timer, flags);
 	release_posix_timer(timer, IT_ID_SET);
-- 
2.20.1

[PATCH 2/2] posix-timers: Use spin_lock_irq() in itimer_delete()

[Sebastian Andrzej Siewior]

itimer_delete() uses spin_lock_irqsave() to obtain a `flags' variable
which can then be passed to unlock_timer(). It uses already spin_lock
locking for the structure instead of lock_timer() because it has a timer
which can not be removed by others at this point. The cleanup is always
performed with enabled interrupts.

Use spin_lock_irq() / spin_unlock_irq() so the `flags' variable can be
removed.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 kernel/time/posix-timers.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c
index caa63e58e3d88..d7f2d91acdac1 100644
--- a/kernel/time/posix-timers.c
+++ b/kernel/time/posix-timers.c
@@ -980,18 +980,16 @@ SYSCALL_DEFINE1(timer_delete, timer_t, timer_id)
  */
 static void itimer_delete(struct k_itimer *timer)
 {
-	unsigned long flags;
-
 retry_delete:
-	spin_lock_irqsave(&timer->it_lock, flags);
+	spin_lock_irq(&timer->it_lock);
 
 	if (timer_delete_hook(timer) == TIMER_RETRY) {
-		unlock_timer(timer, flags);
+		spin_unlock_irq(&timer->it_lock);
 		goto retry_delete;
 	}
 	list_del(&timer->list);
 
-	unlock_timer(timer, flags);
+	spin_unlock_irq(&timer->it_lock);
 	release_posix_timer(timer, IT_ID_SET);
 }
 
-- 
2.20.1

[tip:timers/core] posix-timers: Remove "it_signal = NULL" assignment in itimer_delete()

[tip-bot for Sebastian Andrzej Siewior]

Commit-ID:  12063d431078be73d11cb5e48a17c6db5f0d8254
Gitweb:     https://git.kernel.org/tip/12063d431078be73d11cb5e48a17c6db5f0d8254
Author:     Sebastian Andrzej Siewior <bigeasy@linutronix.de>
AuthorDate: Fri, 21 Jun 2019 16:36:42 +0200
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Sat, 22 Jun 2019 12:14:22 +0200

posix-timers: Remove "it_signal = NULL" assignment in itimer_delete()

itimer_delete() is invoked during do_exit(). At this point it is the
last thread in the group dying and doing the clean up.
Since it is the last thread in the group, there can not be any other
task attempting to lock the itimer which means the NULL assignment (which
avoids lookups in __lock_timer()) is not required.

The assignment and comment was copied in commit 0e568881178ff ("[PATCH]
fix posix-timers to have proper per-process scope") from
sys_timer_delete() which was/is the syscall interface and requires the
assignment.

Remove the superfluous ->it_signal = NULL assignment.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20190621143643.25649-2-bigeasy@linutronix.de

---
 kernel/time/posix-timers.c | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c
index 29176635991f..caa63e58e3d8 100644
--- a/kernel/time/posix-timers.c
+++ b/kernel/time/posix-timers.c
@@ -990,11 +990,6 @@ retry_delete:
 		goto retry_delete;
 	}
 	list_del(&timer->list);
-	/*
-	 * This keeps any tasks waiting on the spin lock from thinking
-	 * they got something (see the lock code above).
-	 */
-	timer->it_signal = NULL;
 
 	unlock_timer(timer, flags);
 	release_posix_timer(timer, IT_ID_SET);

[tip:timers/core] posix-timers: Use spin_lock_irq() in itimer_delete()

[tip-bot for Sebastian Andrzej Siewior]

Commit-ID:  7586addb99322faf4d096fc8beb140f879409212
Gitweb:     https://git.kernel.org/tip/7586addb99322faf4d096fc8beb140f879409212
Author:     Sebastian Andrzej Siewior <bigeasy@linutronix.de>
AuthorDate: Fri, 21 Jun 2019 16:36:43 +0200
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Sat, 22 Jun 2019 12:14:22 +0200

posix-timers: Use spin_lock_irq() in itimer_delete()

itimer_delete() uses spin_lock_irqsave() to obtain a `flags' variable
which can then be passed to unlock_timer(). It uses already spin_lock
locking for the structure instead of lock_timer() because it has a timer
which can not be removed by others at this point. The cleanup is always
performed with enabled interrupts.

Use spin_lock_irq() / spin_unlock_irq() so the `flags' variable can be
removed.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20190621143643.25649-3-bigeasy@linutronix.de

---
 kernel/time/posix-timers.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c
index caa63e58e3d8..d7f2d91acdac 100644
--- a/kernel/time/posix-timers.c
+++ b/kernel/time/posix-timers.c
@@ -980,18 +980,16 @@ retry_delete:
  */
 static void itimer_delete(struct k_itimer *timer)
 {
-	unsigned long flags;
-
 retry_delete:
-	spin_lock_irqsave(&timer->it_lock, flags);
+	spin_lock_irq(&timer->it_lock);
 
 	if (timer_delete_hook(timer) == TIMER_RETRY) {
-		unlock_timer(timer, flags);
+		spin_unlock_irq(&timer->it_lock);
 		goto retry_delete;
 	}
 	list_del(&timer->list);
 
-	unlock_timer(timer, flags);
+	spin_unlock_irq(&timer->it_lock);
 	release_posix_timer(timer, IT_ID_SET);
 }