aboutsummaryrefslogtreecommitdiffstats
path: root/kernel/time
diff options
context:
space:
mode:
authorjohn stultz <johnstul@us.ibm.com>2009-05-01 16:10:25 -0400
committerThomas Gleixner <tglx@linutronix.de>2009-05-02 04:22:27 -0400
commit74a03b69d1b5ce00a568e142ca97e76b7f5239c6 (patch)
tree02bdea43ae6d528dcee97c00c3a8651f8841411a /kernel/time
parent091438dd5668396328a3419abcbc6591159eb8d1 (diff)
clockevents: prevent endless loop in tick_handle_periodic()
tick_handle_periodic() can lock up hard when a one shot clock event device is used in combination with jiffies clocksource. Avoid an endless loop issue by requiring that a highres valid clocksource be installed before we call tick_periodic() in a loop when using ONESHOT mode. The result is we will only increment jiffies once per interrupt until a continuous hardware clocksource is available. Without this, we can run into a endless loop, where each cycle through the loop, jiffies is updated which increments time by tick_period or more (due to clock steering), which can cause the event programming to think the next event was before the newly incremented time and fail causing tick_periodic() to be called again and the whole process loops forever. [ Impact: prevent hard lock up ] Signed-off-by: John Stultz <johnstul@us.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: stable@kernel.org
Diffstat (limited to 'kernel/time')
-rw-r--r--kernel/time/tick-common.c12
1 files changed, 11 insertions, 1 deletions
diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c
index 21a5ca849514..83c4417b6a3c 100644
--- a/kernel/time/tick-common.c
+++ b/kernel/time/tick-common.c
@@ -93,7 +93,17 @@ void tick_handle_periodic(struct clock_event_device *dev)
93 for (;;) { 93 for (;;) {
94 if (!clockevents_program_event(dev, next, ktime_get())) 94 if (!clockevents_program_event(dev, next, ktime_get()))
95 return; 95 return;
96 tick_periodic(cpu); 96 /*
97 * Have to be careful here. If we're in oneshot mode,
98 * before we call tick_periodic() in a loop, we need
99 * to be sure we're using a real hardware clocksource.
100 * Otherwise we could get trapped in an infinite
101 * loop, as the tick_periodic() increments jiffies,
102 * when then will increment time, posibly causing
103 * the loop to trigger again and again.
104 */
105 if (timekeeping_valid_for_hres())
106 tick_periodic(cpu);
97 next = ktime_add(next, tick_period); 107 next = ktime_add(next, tick_period);
98 } 108 }
99} 109}