LKML Archive on lore.kernel.org
 help / Atom feed
* [PATCH] nohz: Fix local_timer_softirq_pending()
@ 2018-07-31 16:13 Anna-Maria Gleixner
  2018-07-31 16:50 ` Paul E. McKenney
                   ` (3 more replies)
  0 siblings, 4 replies; 5+ messages in thread
From: Anna-Maria Gleixner @ 2018-07-31 16:13 UTC (permalink / raw)
  To: linux-kernel
  Cc: bigeasy, tglx, frederic, bristot, paulmck, peterz, Anna-Maria Gleixner

local_timer_softirq_pending() checks whether the timer softirq is
pending with: local_softirq_pending() & TIMER_SOFTIRQ.

This is wrong because TIMER_SOFTIRQ is the softirq number and not a
bitmask. So the test checks for the wrong bit.

Use BIT(TIMER_SOFTIRQ) instead.

Fixes: 5d62c183f9e9 ("nohz: Prevent a timer interrupt storm in tick_nohz_stop_sched_tick()")
Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
---
 kernel/time/tick-sched.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index da9455a6b42b..5b33e2f5c0ed 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -642,7 +642,7 @@ static void tick_nohz_restart(struct tick_sched *ts, ktime_t now)
 
 static inline bool local_timer_softirq_pending(void)
 {
-	return local_softirq_pending() & TIMER_SOFTIRQ;
+	return local_softirq_pending() & BIT(TIMER_SOFTIRQ);
 }
 
 static ktime_t tick_nohz_next_event(struct tick_sched *ts, int cpu)
-- 
2.18.0


^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [PATCH] nohz: Fix local_timer_softirq_pending()
  2018-07-31 16:13 [PATCH] nohz: Fix local_timer_softirq_pending() Anna-Maria Gleixner
@ 2018-07-31 16:50 ` Paul E. McKenney
  2018-07-31 17:07 ` Daniel Bristot de Oliveira
                   ` (2 subsequent siblings)
  3 siblings, 0 replies; 5+ messages in thread
From: Paul E. McKenney @ 2018-07-31 16:50 UTC (permalink / raw)
  To: Anna-Maria Gleixner
  Cc: linux-kernel, bigeasy, tglx, frederic, bristot, peterz

On Tue, Jul 31, 2018 at 06:13:58PM +0200, Anna-Maria Gleixner wrote:
> local_timer_softirq_pending() checks whether the timer softirq is
> pending with: local_softirq_pending() & TIMER_SOFTIRQ.
> 
> This is wrong because TIMER_SOFTIRQ is the softirq number and not a
> bitmask. So the test checks for the wrong bit.
> 
> Use BIT(TIMER_SOFTIRQ) instead.
> 
> Fixes: 5d62c183f9e9 ("nohz: Prevent a timer interrupt storm in tick_nohz_stop_sched_tick()")
> Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>

Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

2729 opportunities to change "1UL << x" to "BIT(x)", including
__raise_softirq_irqoff().  I did the two in RCU.  ;-)

							Thanx, Paul

> ---
>  kernel/time/tick-sched.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
> index da9455a6b42b..5b33e2f5c0ed 100644
> --- a/kernel/time/tick-sched.c
> +++ b/kernel/time/tick-sched.c
> @@ -642,7 +642,7 @@ static void tick_nohz_restart(struct tick_sched *ts, ktime_t now)
> 
>  static inline bool local_timer_softirq_pending(void)
>  {
> -	return local_softirq_pending() & TIMER_SOFTIRQ;
> +	return local_softirq_pending() & BIT(TIMER_SOFTIRQ);
>  }
> 
>  static ktime_t tick_nohz_next_event(struct tick_sched *ts, int cpu)
> -- 
> 2.18.0
> 


^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [PATCH] nohz: Fix local_timer_softirq_pending()
  2018-07-31 16:13 [PATCH] nohz: Fix local_timer_softirq_pending() Anna-Maria Gleixner
  2018-07-31 16:50 ` Paul E. McKenney
@ 2018-07-31 17:07 ` Daniel Bristot de Oliveira
  2018-07-31 17:14 ` Frederic Weisbecker
  2018-07-31 20:13 ` [tip:timers/urgent] " tip-bot for Anna-Maria Gleixner
  3 siblings, 0 replies; 5+ messages in thread
From: Daniel Bristot de Oliveira @ 2018-07-31 17:07 UTC (permalink / raw)
  To: Anna-Maria Gleixner, linux-kernel
  Cc: bigeasy, tglx, frederic, paulmck, peterz

On 07/31/2018 06:13 PM, Anna-Maria Gleixner wrote:
> local_timer_softirq_pending() checks whether the timer softirq is
> pending with: local_softirq_pending() & TIMER_SOFTIRQ.
> 
> This is wrong because TIMER_SOFTIRQ is the softirq number and not a
> bitmask. So the test checks for the wrong bit.
> 
> Use BIT(TIMER_SOFTIRQ) instead.

Reviewed-by: Daniel Bristot de Oliveira <bristot@redhat.com>

Thanks!
-- Daniel

> Fixes: 5d62c183f9e9 ("nohz: Prevent a timer interrupt storm in tick_nohz_stop_sched_tick()")
> Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
> ---
>  kernel/time/tick-sched.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
> index da9455a6b42b..5b33e2f5c0ed 100644
> --- a/kernel/time/tick-sched.c
> +++ b/kernel/time/tick-sched.c
> @@ -642,7 +642,7 @@ static void tick_nohz_restart(struct tick_sched *ts, ktime_t now)
>  
>  static inline bool local_timer_softirq_pending(void)
>  {
> -	return local_softirq_pending() & TIMER_SOFTIRQ;
> +	return local_softirq_pending() & BIT(TIMER_SOFTIRQ);
>  }
>  
>  static ktime_t tick_nohz_next_event(struct tick_sched *ts, int cpu)
> 


^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [PATCH] nohz: Fix local_timer_softirq_pending()
  2018-07-31 16:13 [PATCH] nohz: Fix local_timer_softirq_pending() Anna-Maria Gleixner
  2018-07-31 16:50 ` Paul E. McKenney
  2018-07-31 17:07 ` Daniel Bristot de Oliveira
@ 2018-07-31 17:14 ` Frederic Weisbecker
  2018-07-31 20:13 ` [tip:timers/urgent] " tip-bot for Anna-Maria Gleixner
  3 siblings, 0 replies; 5+ messages in thread
From: Frederic Weisbecker @ 2018-07-31 17:14 UTC (permalink / raw)
  To: Anna-Maria Gleixner; +Cc: linux-kernel, bigeasy, tglx, bristot, paulmck, peterz

On Tue, Jul 31, 2018 at 06:13:58PM +0200, Anna-Maria Gleixner wrote:
> local_timer_softirq_pending() checks whether the timer softirq is
> pending with: local_softirq_pending() & TIMER_SOFTIRQ.
> 
> This is wrong because TIMER_SOFTIRQ is the softirq number and not a
> bitmask. So the test checks for the wrong bit.
> 
> Use BIT(TIMER_SOFTIRQ) instead.
> 
> Fixes: 5d62c183f9e9 ("nohz: Prevent a timer interrupt storm in tick_nohz_stop_sched_tick()")
> Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>

Acked-by: Frederic Weisbecker <frederic@kernel.org>

Thanks!

^ permalink raw reply	[flat|nested] 5+ messages in thread

* [tip:timers/urgent] nohz: Fix local_timer_softirq_pending()
  2018-07-31 16:13 [PATCH] nohz: Fix local_timer_softirq_pending() Anna-Maria Gleixner
                   ` (2 preceding siblings ...)
  2018-07-31 17:14 ` Frederic Weisbecker
@ 2018-07-31 20:13 ` " tip-bot for Anna-Maria Gleixner
  3 siblings, 0 replies; 5+ messages in thread
From: tip-bot for Anna-Maria Gleixner @ 2018-07-31 20:13 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: tglx, linux-kernel, anna-maria, hpa, paulmck, frederic, mingo, bristot

Commit-ID:  80d20d35af1edd632a5e7a3b9c0ab7ceff92769e
Gitweb:     https://git.kernel.org/tip/80d20d35af1edd632a5e7a3b9c0ab7ceff92769e
Author:     Anna-Maria Gleixner <anna-maria@linutronix.de>
AuthorDate: Tue, 31 Jul 2018 18:13:58 +0200
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Tue, 31 Jul 2018 22:08:44 +0200

nohz: Fix local_timer_softirq_pending()

local_timer_softirq_pending() checks whether the timer softirq is
pending with: local_softirq_pending() & TIMER_SOFTIRQ.

This is wrong because TIMER_SOFTIRQ is the softirq number and not a
bitmask. So the test checks for the wrong bit.

Use BIT(TIMER_SOFTIRQ) instead.

Fixes: 5d62c183f9e9 ("nohz: Prevent a timer interrupt storm in tick_nohz_stop_sched_tick()")
Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Acked-by: Frederic Weisbecker <frederic@kernel.org>
Cc: bigeasy@linutronix.de
Cc: peterz@infradead.org
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20180731161358.29472-1-anna-maria@linutronix.de

---
 kernel/time/tick-sched.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index da9455a6b42b..5b33e2f5c0ed 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -642,7 +642,7 @@ static void tick_nohz_restart(struct tick_sched *ts, ktime_t now)
 
 static inline bool local_timer_softirq_pending(void)
 {
-	return local_softirq_pending() & TIMER_SOFTIRQ;
+	return local_softirq_pending() & BIT(TIMER_SOFTIRQ);
 }
 
 static ktime_t tick_nohz_next_event(struct tick_sched *ts, int cpu)

^ permalink raw reply	[flat|nested] 5+ messages in thread

end of thread, back to index

Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2018-07-31 16:13 [PATCH] nohz: Fix local_timer_softirq_pending() Anna-Maria Gleixner
2018-07-31 16:50 ` Paul E. McKenney
2018-07-31 17:07 ` Daniel Bristot de Oliveira
2018-07-31 17:14 ` Frederic Weisbecker
2018-07-31 20:13 ` [tip:timers/urgent] " tip-bot for Anna-Maria Gleixner

LKML Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/lkml/0 lkml/git/0.git
	git clone --mirror https://lore.kernel.org/lkml/1 lkml/git/1.git
	git clone --mirror https://lore.kernel.org/lkml/2 lkml/git/2.git
	git clone --mirror https://lore.kernel.org/lkml/3 lkml/git/3.git
	git clone --mirror https://lore.kernel.org/lkml/4 lkml/git/4.git
	git clone --mirror https://lore.kernel.org/lkml/5 lkml/git/5.git
	git clone --mirror https://lore.kernel.org/lkml/6 lkml/git/6.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 lkml lkml/ https://lore.kernel.org/lkml \
		linux-kernel@vger.kernel.org linux-kernel@archiver.kernel.org
	public-inbox-index lkml


Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-kernel


AGPL code for this site: git clone https://public-inbox.org/ public-inbox