[PATCH v2] hrtimer: Add a missing bracket and hide `migration_base' on !SMP

From: Sebastian Andrzej Siewior
Date: Wed Sep 04 2019 - 10:55:32 EST

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 <bigeasy@xxxxxxxxxxxxx>
- 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)) {