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From: Sebastian Andrzej Siewior <>
To: Thomas Gleixner <>
Cc:, Julien Grall <>
Subject: [PATCH v2] hrtimer: Add a missing bracket and hide `migration_base' on !SMP
Date: Wed, 4 Sep 2019 16:55:27 +0200
Message-ID: <> (raw)
In-Reply-To: <>

The recent change to avoid taking the expiry lock when a 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 <>
	- use is_migration_base() as a helper function
	- slightly reword the commit message

 kernel/time/hrtimer.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
index f5a1a5e16216c..eaf31ac38efbb 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -140,6 +140,11 @@ static struct hrtimer_cpu_base migration_cpu_base = {
 #define migration_base	migration_cpu_base.clock_base[0]
+static bool is_migration_base(struct hrtimer_clock_base *base)
+	return base == &migration_base;
  * We are using hashed locking: holding per_cpu(hrtimer_bases)[n].lock
  * means that all timers which are tied to this base via timer->base are
@@ -264,6 +269,11 @@ switch_hrtimer_base(struct hrtimer *timer, struct hrtimer_clock_base *base,
 #else /* CONFIG_SMP */
+static bool is_migration_base(struct hrtimer_clock_base *base)
+	return false;
 static inline struct hrtimer_clock_base *
 lock_hrtimer_base(const struct hrtimer *timer, unsigned long *flags)
@@ -1221,7 +1231,7 @@ void hrtimer_cancel_wait_running(const struct hrtimer *timer)
 	 * 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)
+	if (!timer->is_soft || is_migration_base(base)) {

      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     ` [PATCH] hrtimer: Add a missing bracket and hide `migration_base' on !SMP Sebastian Andrzej Siewior
2019-09-04 14:39       ` Thomas Gleixner
2019-09-04 14:55         ` Sebastian Andrzej Siewior [this message]

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