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authorArtem Pisarenko <artem.k.pisarenko@gmail.com>2018-10-17 14:24:20 +0600
committerPaolo Bonzini <pbonzini@redhat.com>2018-10-19 13:44:03 +0200
commite81f86790f561437b70549aff05433731b464e62 (patch)
tree360c0913976ed5aca468c4bd7d1490758395d9ce /util
parent89a603a0c80ae3d6a8711571550b2ae9a01ea909 (diff)
qemu-timer: avoid checkpoints for virtual clock timers in external subsystems
Adds EXTERNAL attribute definition to qemu timers subsystem and assigns it to virtual clock timers, used in slirp (ICMP IPv6) and ui (key queue). Virtual clock processing in rr mode can use this attribute instead of a separate clock type. Fixes: 87f4fe7653baf55b5c2f2753fe6003f473c07342 Fixes: 775a412bf83f6bc0c5c02091ee06cf649b34c593 Fixes: 9888091404a702d7ec79d51b088d994b9fc121bd Signed-off-by: Artem Pisarenko <artem.k.pisarenko@gmail.com> Message-Id: <e771f96ab94e86b54b9a783c974f2af3009fe5d1.1539764043.git.artem.k.pisarenko@gmail.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'util')
-rw-r--r--util/qemu-timer.c50
1 files changed, 43 insertions, 7 deletions
diff --git a/util/qemu-timer.c b/util/qemu-timer.c
index 04527a343f..1cc1b2f2c3 100644
--- a/util/qemu-timer.c
+++ b/util/qemu-timer.c
@@ -489,6 +489,7 @@ bool timerlist_run_timers(QEMUTimerList *timer_list)
bool progress = false;
QEMUTimerCB *cb;
void *opaque;
+ bool need_replay_checkpoint = false;
if (!atomic_read(&timer_list->active_timers)) {
return false;
@@ -504,8 +505,15 @@ bool timerlist_run_timers(QEMUTimerList *timer_list)
break;
default:
case QEMU_CLOCK_VIRTUAL:
- if (!replay_checkpoint(CHECKPOINT_CLOCK_VIRTUAL)) {
- goto out;
+ if (replay_mode != REPLAY_MODE_NONE) {
+ /* Checkpoint for virtual clock is redundant in cases where
+ * it's being triggered with only non-EXTERNAL timers, because
+ * these timers don't change guest state directly.
+ * Since it has conditional dependence on specific timers, it is
+ * subject to race conditions and requires special handling.
+ * See below.
+ */
+ need_replay_checkpoint = true;
}
break;
case QEMU_CLOCK_HOST:
@@ -520,14 +528,39 @@ bool timerlist_run_timers(QEMUTimerList *timer_list)
break;
}
+ /*
+ * Extract expired timers from active timers list and and process them.
+ *
+ * In rr mode we need "filtered" checkpointing for virtual clock. The
+ * checkpoint must be recorded/replayed before processing any non-EXTERNAL timer,
+ * and that must only be done once since the clock value stays the same. Because
+ * non-EXTERNAL timers may appear in the timers list while it being processed,
+ * the checkpoint can be issued at a time until no timers are left and we are
+ * done".
+ */
current_time = qemu_clock_get_ns(timer_list->clock->type);
- for(;;) {
- qemu_mutex_lock(&timer_list->active_timers_lock);
- ts = timer_list->active_timers;
+ qemu_mutex_lock(&timer_list->active_timers_lock);
+ while ((ts = timer_list->active_timers)) {
if (!timer_expired_ns(ts, current_time)) {
- qemu_mutex_unlock(&timer_list->active_timers_lock);
+ /* No expired timers left. The checkpoint can be skipped
+ * if no timers fired or they were all external.
+ */
break;
}
+ if (need_replay_checkpoint
+ && !(ts->attributes & QEMU_TIMER_ATTR_EXTERNAL)) {
+ /* once we got here, checkpoint clock only once */
+ need_replay_checkpoint = false;
+ qemu_mutex_unlock(&timer_list->active_timers_lock);
+ if (!replay_checkpoint(CHECKPOINT_CLOCK_VIRTUAL)) {
+ goto out;
+ }
+ qemu_mutex_lock(&timer_list->active_timers_lock);
+ /* The lock was released; start over again in case the list was
+ * modified.
+ */
+ continue;
+ }
/* remove timer from the list before calling the callback */
timer_list->active_timers = ts->next;
@@ -535,12 +568,15 @@ bool timerlist_run_timers(QEMUTimerList *timer_list)
ts->expire_time = -1;
cb = ts->cb;
opaque = ts->opaque;
- qemu_mutex_unlock(&timer_list->active_timers_lock);
/* run the callback (the timer list can be modified) */
+ qemu_mutex_unlock(&timer_list->active_timers_lock);
cb(opaque);
+ qemu_mutex_lock(&timer_list->active_timers_lock);
+
progress = true;
}
+ qemu_mutex_unlock(&timer_list->active_timers_lock);
out:
qemu_event_set(&timer_list->timers_done_ev);