From 26456f87aca7157c057de65c9414b37f1ab881d1 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Wed, 27 Dec 2017 21:37:25 +0100 Subject: 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: 500462a9de65 ("timers: Switch to a non-cascading wheel") Reported-by: Paul E. McKenney Signed-off-by: Thomas Gleixner Cc: Peter Zijlstra Cc: Frederic Weisbecker Cc: Sebastian Siewior Cc: Anna-Maria Gleixner Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/alpine.DEB.2.20.1712272152200.2431@nanos --- include/linux/cpuhotplug.h | 2 +- include/linux/timer.h | 4 +++- kernel/cpu.c | 4 ++-- kernel/time/timer.c | 15 +++++++++++++++ 4 files changed, 21 insertions(+), 4 deletions(-) diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h index 201ab7267986..1a32e558eb11 100644 --- a/include/linux/cpuhotplug.h +++ b/include/linux/cpuhotplug.h @@ -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, diff --git a/include/linux/timer.h b/include/linux/timer.h index 04af640ea95b..2448f9cc48a3 100644 --- a/include/linux/timer.h +++ b/include/linux/timer.h @@ -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 diff --git a/kernel/cpu.c b/kernel/cpu.c index 41376c3ac93b..97858477e586 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -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 */ diff --git a/kernel/time/timer.c b/kernel/time/timer.c index 19a9c3da7698..6be576e02209 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -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; -- cgit v1.2.3