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qemu-timer: do not take the lock in timer_pending

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We can deduce the result from expire_time, by making it always -1 if
the timer is not in the active_timers list.  We need to check against
negative times passed to timer_mod_ns; clamping them to zero is not
a problem because the only clock that has a zero value at VM startup
is QEMU_CLOCK_VIRTUAL, and it is monotonic so it cannot be non-zero.
QEMU_CLOCK_HOST, instead, is not monotonic but it cannot go to negative
values unless the host time is seriously screwed up and points to
the 1960s.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Paolo Bonzini 2013-09-12 11:02:20 +02:00 committed by Stefan Hajnoczi
parent 978f2205c7
commit 3db1ee7c2a
1 changed files with 5 additions and 14 deletions
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19
qemu-timer.c
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@ -312,6 +312,7 @@ void timer_init(QEMUTimer *ts,
ts->cb = cb;
ts->opaque = opaque;
ts->scale = scale;
ts->expire_time = -1;
}
void timer_free(QEMUTimer *ts)
@ -323,6 +324,7 @@ static void timer_del_locked(QEMUTimerList *timer_list, QEMUTimer *ts)
{
QEMUTimer **pt, *t;
ts->expire_time = -1;
pt = &timer_list->active_timers;
for(;;) {
t = *pt;
@ -365,7 +367,7 @@ void timer_mod_ns(QEMUTimer *ts, int64_t expire_time)
}
pt = &t->next;
}
ts->expire_time = expire_time;
ts->expire_time = MAX(expire_time, 0);
ts->next = *pt;
*pt = ts;
qemu_mutex_unlock(&timer_list->active_timers_lock);
@ -385,19 +387,7 @@ void timer_mod(QEMUTimer *ts, int64_t expire_time)
bool timer_pending(QEMUTimer *ts)
{
QEMUTimerList *timer_list = ts->timer_list;
QEMUTimer *t;
bool found = false;
qemu_mutex_lock(&timer_list->active_timers_lock);
for (t = timer_list->active_timers; t != NULL; t = t->next) {
if (t == ts) {
found = true;
break;
}
}
qemu_mutex_unlock(&timer_list->active_timers_lock);
return found;
return ts->expire_time >= 0;
}
bool timer_expired(QEMUTimer *timer_head, int64_t current_time)
@ -429,6 +419,7 @@ bool timerlist_run_timers(QEMUTimerList *timer_list)
/* remove timer from the list before calling the callback */
timer_list->active_timers = ts->next;
ts->next = NULL;
ts->expire_time = -1;
cb = ts->cb;
opaque = ts->opaque;
qemu_mutex_unlock(&timer_list->active_timers_lock);