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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: linux-kernel@vger.kernel.org
Cc: Thomas Gleixner <tglx@linutronix.de>,
	Julien Grall <julien.grall@arm.com>
Subject: [PATCH] hrtimer: Add a missing bracket and hide `migration_base' on !SMP
Date: Wed, 4 Sep 2019 16:15:40 +0200
Message-ID: <20190904141540.xucehzbndjmgkrio@linutronix.de> (raw)
In-Reply-To: <156652633520.11649.15892124550118329976.tip-bot2@tip-bot2>

Commit
   68b2c8c1e4210 ("hrtimer: Don't take expiry_lock when timer is currently migrated")

missed to add a bracket at the end of the if statement leading to
compile errors.
Since that commit the variable `migration_base' is always used but only
available on SMP configuration thus leading to another compile error.
The changelog says
  "The timer base and base->cpu_base cannot be NULL in the code path"

so it is safe to limit this check to SMP configurations only.

Add the missing bracket to the if statement and hide `migration_base'
behind CONFIG_SMP bars.

Fixes: 68b2c8c1e4210 ("hrtimer: Don't take expiry_lock when timer is currently migrated")
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 kernel/time/hrtimer.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
index f5a1a5e16216c..bc84c74ae5b96 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -1216,12 +1216,16 @@ void hrtimer_cancel_wait_running(const struct hrtimer *timer)
 {
 	/* Lockless read. Prevent the compiler from reloading it below */
 	struct hrtimer_clock_base *base = READ_ONCE(timer->base);
+	bool is_migration_base = false;
 
 	/*
 	 * Just relax if the timer expires in hard interrupt context or if
 	 * it is currently on the migration base.
 	 */
-	if (!timer->is_soft || base == &migration_base)
+#ifdef CONFIG_SMP
+	is_migration_base = base == &migration_base;
+#endif
+	if (timer->is_soft || is_migration_base) {
 		cpu_relax();
 		return;
 	}
-- 
2.23.0

  reply index

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-21  9:24 [RT PATCH 0/3] hrtimer: RT fixes for hrtimer_grab_expiry_lock() Julien Grall
2019-08-21  9:24 ` [RT PATCH 1/3] hrtimer: Use READ_ONCE to access timer->base in hrimer_grab_expiry_lock() Julien Grall
2019-08-21 13:44   ` Sebastian Andrzej Siewior
2019-08-21 13:50     ` Thomas Gleixner
2019-08-21 13:59       ` Sebastian Andrzej Siewior
2019-09-26 21:47       ` Eric Dumazet
2019-08-23  2:12   ` [tip: timers/core] hrtimer: Protect lockless access to timer->base tip-bot2 for Julien Grall
2019-08-21  9:24 ` [RT PATCH 2/3] hrtimer: Don't grab the expiry lock for non-soft hrtimer Julien Grall
2019-08-21 13:49   ` Sebastian Andrzej Siewior
2019-08-21  9:24 ` [RT PATCH 3/3] hrtimer: Prevent using uninitialized spin_lock in hrtimer_grab_expiry_lock() Julien Grall
2019-08-21 14:02   ` Thomas Gleixner
2019-08-22 10:59     ` Julien Grall
2019-08-23  2:12   ` [tip: timers/core] hrtimer: Don't take expiry_lock when timer is currently migrated tip-bot2 for Julien Grall
2019-09-04 14:15     ` Sebastian Andrzej Siewior [this message]
2019-09-04 14:39       ` [PATCH] hrtimer: Add a missing bracket and hide `migration_base' on !SMP Thomas Gleixner
2019-09-04 14:55         ` [PATCH v2] " Sebastian Andrzej Siewior

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