hrtimers: Move SMP function call to thread context
smp_call_function_* must not be called from softirq context.
But clock_was_set() which calls on_each_cpu() is called from softirq
context to implement a delayed clock_was_set() for the timer interrupt
handler. Though that almost never gets invoked. A recent change in the
resume code uses the softirq based delayed clock_was_set to support
Xens resume mechanism.
linux-next contains a new warning which warns if smp_call_function_*
is called from softirq context which gets triggered by that Xen
change.
Fix this by moving the delayed clock_was_set() call to a work context.
Reported-and-tested-by: Artem Savkov <artem.savkov@gmail.com>
Reported-by: Sasha Levin <sasha.levin@oracle.com>
Cc: David Vrabel <david.vrabel@citrix.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: H. Peter Anvin <hpa@zytor.com>,
Cc: Konrad Wilk <konrad.wilk@oracle.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: xen-devel@lists.xen.org
Cc: stable@vger.kernel.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index e86827e..b9b9420 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -721,17 +721,20 @@
return 1;
}
+static void clock_was_set_work(struct work_struct *work)
+{
+ clock_was_set();
+}
+
+static DECLARE_WORK(hrtimer_work, clock_was_set_work);
+
/*
- * Called from timekeeping code to reprogramm the hrtimer interrupt
- * device. If called from the timer interrupt context we defer it to
- * softirq context.
+ * Called from timekeeping and resume code to reprogramm the hrtimer
+ * interrupt device on all cpus.
*/
void clock_was_set_delayed(void)
{
- struct hrtimer_cpu_base *cpu_base = &__get_cpu_var(hrtimer_bases);
-
- cpu_base->clock_was_set = 1;
- __raise_softirq_irqoff(HRTIMER_SOFTIRQ);
+ schedule_work(&hrtimer_work);
}
#else
@@ -775,12 +778,7 @@
* During resume we might have to reprogram the high resolution timer
* interrupt on all online CPUs. However, all other CPUs will be
* stopped with IRQs interrupts disabled so the clock_was_set() call
- * must be deferred to the softirq.
- *
- * The one-shot timer has already been programmed to fire immediately
- * (see tick_resume_oneshot()) and this interrupt will trigger the
- * softirq to run early enough to correctly reprogram the timers on
- * all CPUs.
+ * must be deferred.
*/
void hrtimers_resume(void)
{
@@ -789,8 +787,10 @@
WARN_ONCE(!irqs_disabled(),
KERN_INFO "hrtimers_resume() called with IRQs enabled!");
- cpu_base->clock_was_set = 1;
- __raise_softirq_irqoff(HRTIMER_SOFTIRQ);
+ /* Retrigger on the local CPU */
+ retrigger_next_event(NULL);
+ /* And schedule a retrigger for all others */
+ clock_was_set_delayed();
}
static inline void timer_stats_hrtimer_set_start_info(struct hrtimer *timer)
@@ -1441,13 +1441,6 @@
static void run_hrtimer_softirq(struct softirq_action *h)
{
- struct hrtimer_cpu_base *cpu_base = &__get_cpu_var(hrtimer_bases);
-
- if (cpu_base->clock_was_set) {
- cpu_base->clock_was_set = 0;
- clock_was_set();
- }
-
hrtimer_peek_ahead_timers();
}