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authorSebastien Dugue <sebastien.dugue@bull.net>2008-12-01 08:09:07 -0500
committerIngo Molnar <mingo@elte.hu>2009-01-30 16:35:29 -0500
commit94df7de0289bc2df3d6e85cd2ece52bf42682f45 (patch)
treeb3f614b015adfb9574959687bb9b7ac4c884e23a /kernel/time
parent7f22391cbe82a80a9f891d8bd10fc28ff248d1e2 (diff)
hrtimers: allow the hot-unplugging of all cpus
Impact: fix CPU hotplug hang on Power6 testbox On architectures that support offlining all cpus (at least powerpc/pseries), hot-unpluging the tick_do_timer_cpu can result in a system hang. This comes from the fact that if the cpu going down happens to be the cpu doing the tick, then as the tick_do_timer_cpu handover happens after the cpu is dead (via the CPU_DEAD notification), we're left without ticks, jiffies are frozen and any task relying on timers (msleep, ...) is stuck. That's particularly the case for the cpu looping in __cpu_die() waiting for the dying cpu to be dead. This patch addresses this by having the tick_do_timer_cpu handover happen earlier during the CPU_DYING notification. For this, a new clockevent notification type is introduced (CLOCK_EVT_NOTIFY_CPU_DYING) which is triggered in hrtimer_cpu_notify(). Signed-off-by: Sebastien Dugue <sebastien.dugue@bull.net> Cc: <stable@kernel.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/time')
-rw-r--r--kernel/time/tick-common.c26
1 files changed, 19 insertions, 7 deletions
diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c
index 63e05d423a09..21a5ca849514 100644
--- a/kernel/time/tick-common.c
+++ b/kernel/time/tick-common.c
@@ -274,6 +274,21 @@ out_bc:
274} 274}
275 275
276/* 276/*
277 * Transfer the do_timer job away from a dying cpu.
278 *
279 * Called with interrupts disabled.
280 */
281static void tick_handover_do_timer(int *cpup)
282{
283 if (*cpup == tick_do_timer_cpu) {
284 int cpu = cpumask_first(cpu_online_mask);
285
286 tick_do_timer_cpu = (cpu < nr_cpu_ids) ? cpu :
287 TICK_DO_TIMER_NONE;
288 }
289}
290
291/*
277 * Shutdown an event device on a given cpu: 292 * Shutdown an event device on a given cpu:
278 * 293 *
279 * This is called on a life CPU, when a CPU is dead. So we cannot 294 * This is called on a life CPU, when a CPU is dead. So we cannot
@@ -297,13 +312,6 @@ static void tick_shutdown(unsigned int *cpup)
297 clockevents_exchange_device(dev, NULL); 312 clockevents_exchange_device(dev, NULL);
298 td->evtdev = NULL; 313 td->evtdev = NULL;
299 } 314 }
300 /* Transfer the do_timer job away from this cpu */
301 if (*cpup == tick_do_timer_cpu) {
302 int cpu = cpumask_first(cpu_online_mask);
303
304 tick_do_timer_cpu = (cpu < nr_cpu_ids) ? cpu :
305 TICK_DO_TIMER_NONE;
306 }
307 spin_unlock_irqrestore(&tick_device_lock, flags); 315 spin_unlock_irqrestore(&tick_device_lock, flags);
308} 316}
309 317
@@ -357,6 +365,10 @@ static int tick_notify(struct notifier_block *nb, unsigned long reason,
357 tick_broadcast_oneshot_control(reason); 365 tick_broadcast_oneshot_control(reason);
358 break; 366 break;
359 367
368 case CLOCK_EVT_NOTIFY_CPU_DYING:
369 tick_handover_do_timer(dev);
370 break;
371
360 case CLOCK_EVT_NOTIFY_CPU_DEAD: 372 case CLOCK_EVT_NOTIFY_CPU_DEAD:
361 tick_shutdown_broadcast_oneshot(dev); 373 tick_shutdown_broadcast_oneshot(dev);
362 tick_shutdown_broadcast(dev); 374 tick_shutdown_broadcast(dev);