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timers: Reinitialize per cpu bases on hotplug 

The timer wheel bases are not (re)initialized on CPU hotplug. That leaves
them with a potentially stale clk and next_expiry valuem, which can cause
trouble then the CPU is plugged.

Add a prepare callback which forwards the clock, sets next_expiry to far in
the future and reset the control flags to a known state.

Set base->must_forward_clk so the first timer which is queued will try to
forward the clock to current jiffies.

Fixes: 500462a9de ("timers: Switch to a non-cascading wheel")
Reported-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Anna-Maria Gleixner <anna-maria@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/alpine.DEB.2.20.1712272152200.2431@nanos
zero-colors
Thomas Gleixner 2017-12-27 21:37:25 +01:00
parent ced6d5c11d
commit 26456f87ac
4 changed files with 21 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/linux/cpuhotplug.h
View File

@ -86,7 +86,7 @@ enum cpuhp_state {
CPUHP_MM_ZSWP_POOL_PREPARE,
CPUHP_KVM_PPC_BOOK3S_PREPARE,
CPUHP_ZCOMP_PREPARE,
CPUHP_TIMERS_DEAD,
CPUHP_TIMERS_PREPARE,
CPUHP_MIPS_SOC_PREPARE,
CPUHP_BP_PREPARE_DYN,
CPUHP_BP_PREPARE_DYN_END = CPUHP_BP_PREPARE_DYN + 20,

4
include/linux/timer.h
View File

@ -207,9 +207,11 @@ unsigned long round_jiffies_up(unsigned long j);
unsigned long round_jiffies_up_relative(unsigned long j);
#ifdef CONFIG_HOTPLUG_CPU
int timers_prepare_cpu(unsigned int cpu);
int timers_dead_cpu(unsigned int cpu);
#else
#define timers_dead_cpu NULL
#define timers_prepare_cpu NULL
#define timers_dead_cpu NULL
#endif
#endif

4
kernel/cpu.c
View File

@ -1277,9 +1277,9 @@ static struct cpuhp_step cpuhp_bp_states[] = {
* before blk_mq_queue_reinit_notify() from notify_dead(),
* otherwise a RCU stall occurs.
*/
[CPUHP_TIMERS_DEAD] = {
[CPUHP_TIMERS_PREPARE] = {
.name = "timers:dead",
.startup.single = NULL,
.startup.single = timers_prepare_cpu,
.teardown.single = timers_dead_cpu,
},
/* Kicks the plugged cpu into life */

15
kernel/time/timer.c
View File

@ -1853,6 +1853,21 @@ static void migrate_timer_list(struct timer_base *new_base, struct hlist_head *h
}
}
int timers_prepare_cpu(unsigned int cpu)
{
struct timer_base *base;
int b;
for (b = 0; b < NR_BASES; b++) {
base = per_cpu_ptr(&timer_bases[b], cpu);
base->clk = jiffies;
base->next_expiry = base->clk + NEXT_TIMER_MAX_DELTA;
base->is_idle = false;
base->must_forward_clk = true;
}
return 0;
}
int timers_dead_cpu(unsigned int cpu)
{
struct timer_base *old_base;