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timers: Reinitialize per cpu bases on hotplug

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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 <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: Sebastian Siewior <[email protected]>
Cc: Anna-Maria Gleixner <[email protected]>
Cc: [email protected]
Link: https://lkml.kernel.org/r/alpine.DEB.2.20.1712272152200.2431@nanos
This commit is contained in:
Thomas Gleixner 2017-12-27 21:37:25 +01:00
commit 26456f87ac
4 changed files with 21 additions and 4 deletions
Download patch file Download diff file Expand all files Collapse all files

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;