projects/linux·commit 87a54cae

Merge branch 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

87a54cae · Linus Torvalds <[email protected]> · 2014-04-17 16:19:10 -07:00

Pull timer fixes from Thomas Gleixner:
 "Viresh unearthed the following three hickups in the timer/timekeeping
  code:

   - Negated check for the result of a clock event selection

   - A missing early exit in the jiffies update path which causes
     update_wall_time to be called for nothing causing lock contention
     and wasted cycles in the timer interrupt

   - Checking a variable in the NOHZ code enable code for true which can
     only be set by that very code after the check succeeds.  That
     results in a rock solid runtime disablement of that feature"

* 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  tick-sched: Check tick_nohz_enabled in tick_nohz_switch_to_nohz()
  tick-sched: Don't call update_wall_time() when delta is lesser than tick_period
  tick-common: Fix wrong check in tick_check_replacement()
Commit
87a54cae0ba094de2ddb7e5f429fd32b965a2fbf
Parents
81cef0fe · 27630532

Merge commit. Changes below are compared with the first parent: 81cef0fe.

Changes

2 files changed · +5 −2

FileStatusAddDelContent
kernel/time/tick-common.cmodified+1−1View file
kernel/time/tick-sched.cmodified+4−1View file

kernel/time/tick-common.c

View file
diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c
index 0156612..0a0608e 100644
--- a/kernel/time/tick-common.c
+++ b/kernel/time/tick-common.c
@@ -276,7 +276,7 @@ static bool tick_check_preferred(struct clock_event_device *curdev,
bool tick_check_replacement(struct clock_event_device *curdev,
struct clock_event_device *newdev)
{
- if (tick_check_percpu(curdev, newdev, smp_processor_id()))
+ if (!tick_check_percpu(curdev, newdev, smp_processor_id()))
return false;
return tick_check_preferred(curdev, newdev);

kernel/time/tick-sched.c

View file
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 9f8af69..6558b7a 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -84,6 +84,9 @@ static void tick_do_update_jiffies64(ktime_t now)
/* Keep the tick_next_period variable up to date */
tick_next_period = ktime_add(last_jiffies_update, tick_period);
+ } else {
+ write_sequnlock(&jiffies_lock);
+ return;
}
write_sequnlock(&jiffies_lock);
update_wall_time();
@@ -967,7 +970,7 @@ static void tick_nohz_switch_to_nohz(void)
struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);
ktime_t next;
- if (!tick_nohz_active)
+ if (!tick_nohz_enabled)
return;
local_irq_disable();