If stop_timer() is called between when a timer interrupt
arrives (and TIMER_SOFTIRQ is raised) and when softirqs are
checked and handled, the timer that has fire is (right in
stop_timer()) deactivated, and the handler for that
occurrence of the interrupt never executed.
This happens, e.g. to timers stopped during the wakeup
from idle (e.g., C-states, on x86) path.
To fix that, don't deactivate a timer, while stopping it,
if it has expired. On the contrary, when that happens,
(re-)raise the timer softirq, to make sure the handler is
invoked.
Signed-off-by: Dario Faggioli <dario.faggi...@citrix.com>
---
Cc: Andrew Cooper <andrew.coop...@citrix.com>
Cc: George Dunlap <george.dun...@eu.citrix.com>
Cc: Jan Beulich <jbeul...@suse.com>
Cc: Stefano Stabellini <sstabell...@kernel.org>
Cc: Julien Grall <julien.gr...@arm.com>
Cc: Tim Deegan <t...@xen.org>
---
xen/common/timer.c | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)
diff --git a/xen/common/timer.c b/xen/common/timer.c
index d9ff669..b1d1511 100644
--- a/xen/common/timer.c
+++ b/xen/common/timer.c
@@ -217,7 +217,7 @@ static inline void activate_timer(struct timer *timer)
timer->status = TIMER_STATUS_invalid;
list_del(&timer->inactive);
- if ( add_entry(timer) )
+ if ( add_entry(timer) || timer->expires <= NOW() )
cpu_raise_softirq(timer->cpu, TIMER_SOFTIRQ);
}
@@ -326,7 +326,17 @@ void stop_timer(struct timer *timer)
return;
if ( active_timer(timer) )
- deactivate_timer(timer);
+ {
+ /*
+ * If the timer is expired already, 'call' the softirq handler to
+ * execute it (it will leave it inactive after that). If not, just
+ * deactivate it.
+ */
+ if ( timer->expires <= NOW() )
+ cpu_raise_softirq(timer->cpu, TIMER_SOFTIRQ);
+ else
+ deactivate_timer(timer);
+ }
timer_unlock_irqrestore(timer, flags);
}
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