timers: Reinitialize per cpu bases on hotplug
commit 26456f87aca7157c057de65c9414b37f1ab881d1 upstream.
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 <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>
Link: https://lkml.kernel.org/r/alpine.DEB.2.20.1712272152200.2431@nanos
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index 965cc56..c9447a6 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -48,7 +48,7 @@
CPUHP_ARM_SHMOBILE_SCU_PREPARE,
CPUHP_SH_SH3X_PREPARE,
CPUHP_BLK_MQ_PREPARE,
- CPUHP_TIMERS_DEAD,
+ CPUHP_TIMERS_PREPARE,
CPUHP_NOTF_ERR_INJ_PREPARE,
CPUHP_MIPS_SOC_PREPARE,
CPUHP_BRINGUP_CPU,
diff --git a/include/linux/timer.h b/include/linux/timer.h
index 51d601f..ec86e4e 100644
--- a/include/linux/timer.h
+++ b/include/linux/timer.h
@@ -274,9 +274,11 @@
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 e1436ca..802eb33 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -1309,9 +1309,9 @@
* 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 26c2f65..e872f7f 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -1851,6 +1851,21 @@
}
}
+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;