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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
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@ -86,7 +86,7 @@ enum cpuhp_state {
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CPUHP_MM_ZSWP_POOL_PREPARE,
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CPUHP_KVM_PPC_BOOK3S_PREPARE,
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CPUHP_ZCOMP_PREPARE,
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CPUHP_TIMERS_DEAD,
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CPUHP_TIMERS_PREPARE,
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CPUHP_MIPS_SOC_PREPARE,
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CPUHP_BP_PREPARE_DYN,
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CPUHP_BP_PREPARE_DYN_END = CPUHP_BP_PREPARE_DYN + 20,
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@ -207,9 +207,11 @@ unsigned long round_jiffies_up(unsigned long j);
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unsigned long round_jiffies_up_relative(unsigned long j);
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#ifdef CONFIG_HOTPLUG_CPU
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int timers_prepare_cpu(unsigned int cpu);
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int timers_dead_cpu(unsigned int cpu);
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#else
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#define timers_dead_cpu NULL
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#define timers_prepare_cpu NULL
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#define timers_dead_cpu NULL
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#endif
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#endif
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@ -1277,9 +1277,9 @@ static struct cpuhp_step cpuhp_bp_states[] = {
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* before blk_mq_queue_reinit_notify() from notify_dead(),
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* otherwise a RCU stall occurs.
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*/
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[CPUHP_TIMERS_DEAD] = {
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[CPUHP_TIMERS_PREPARE] = {
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.name = "timers:dead",
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.startup.single = NULL,
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.startup.single = timers_prepare_cpu,
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.teardown.single = timers_dead_cpu,
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},
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/* Kicks the plugged cpu into life */
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@ -1853,6 +1853,21 @@ static void migrate_timer_list(struct timer_base *new_base, struct hlist_head *h
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}
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}
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int timers_prepare_cpu(unsigned int cpu)
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{
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struct timer_base *base;
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int b;
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for (b = 0; b < NR_BASES; b++) {
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base = per_cpu_ptr(&timer_bases[b], cpu);
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base->clk = jiffies;
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base->next_expiry = base->clk + NEXT_TIMER_MAX_DELTA;
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base->is_idle = false;
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base->must_forward_clk = true;
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}
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return 0;
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}
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int timers_dead_cpu(unsigned int cpu)
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{
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struct timer_base *old_base;
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