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timers/core: Convert to hotplug state machine 

When tearing down, call timers_dead_cpu() before notify_dead().
There is a hidden dependency between:

 - timers
 - block multiqueue
 - rcutree

If timers_dead_cpu() comes later than blk_mq_queue_reinit_notify()
that latter function causes a RCU stall.

Signed-off-by: Richard Cochran <rcochran@linutronix.de>
Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160713153337.566790058@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Richard Cochran 2016-07-13 17:16:59 +00:00 committed by Ingo Molnar
parent 27590dc17b
commit 24f73b9971
4 changed files with 14 additions and 23 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
include/linux/cpuhotplug.h
View File

@ -16,6 +16,7 @@ enum cpuhp_state {
CPUHP_X86_APB_DEAD,
CPUHP_WORKQUEUE_PREP,
CPUHP_HRTIMERS_PREPARE,
CPUHP_TIMERS_DEAD,
CPUHP_NOTIFY_PREPARE,
CPUHP_BRINGUP_CPU,
CPUHP_AP_IDLE_DEAD,

6
include/linux/timer.h
View File

@ -273,4 +273,10 @@ unsigned long __round_jiffies_up_relative(unsigned long j, int cpu);
unsigned long round_jiffies_up(unsigned long j);
unsigned long round_jiffies_up_relative(unsigned long j);
#ifdef CONFIG_HOTPLUG_CPU
int timers_dead_cpu(unsigned int cpu);
#else
#define timers_dead_cpu NULL
#endif
#endif

5
kernel/cpu.c
View File

@ -1195,6 +1195,11 @@ static struct cpuhp_step cpuhp_bp_states[] = {
.startup = hrtimers_prepare_cpu,
.teardown = hrtimers_dead_cpu,
},
[CPUHP_TIMERS_DEAD] = {
.name = "timers dead",
.startup = NULL,
.teardown = timers_dead_cpu,
},
/*
* Preparatory and dead notifiers. Will be replaced once the notifiers
* are converted to states.

25
kernel/time/timer.c
View File

@ -1804,7 +1804,7 @@ static void migrate_timer_list(struct timer_base *new_base, struct hlist_head *h
}
}
static void migrate_timers(int cpu)
int timers_dead_cpu(unsigned int cpu)
{
struct timer_base *old_base;
struct timer_base *new_base;
@ -1831,29 +1831,9 @@ static void migrate_timers(int cpu)
spin_unlock_irq(&new_base->lock);
put_cpu_ptr(&timer_bases);
}
return 0;
}
static int timer_cpu_notify(struct notifier_block *self,
unsigned long action, void *hcpu)
{
switch (action) {
case CPU_DEAD:
case CPU_DEAD_FROZEN:
migrate_timers((long)hcpu);
break;
default:
break;
}
return NOTIFY_OK;
}
static inline void timer_register_cpu_notifier(void)
{
cpu_notifier(timer_cpu_notify, 0);
}
#else
static inline void timer_register_cpu_notifier(void) { }
#endif /* CONFIG_HOTPLUG_CPU */
static void __init init_timer_cpu(int cpu)
@ -1881,7 +1861,6 @@ void __init init_timers(void)
{
init_timer_cpus();
init_timer_stats();
timer_register_cpu_notifier();
open_softirq(TIMER_SOFTIRQ, run_timer_softirq);
}