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[Qemu-devel] [PULL 09/17] timer: make qemu_clock_enable sync between dis
From: |
Paolo Bonzini |
Subject: |
[Qemu-devel] [PULL 09/17] timer: make qemu_clock_enable sync between disable and timer's cb |
Date: |
Thu, 17 Oct 2013 17:48:47 +0200 |
From: Liu Ping Fan <address@hidden>
After disabling the QemuClock, we should make sure that no QemuTimers
are still in flight. To implement that with light overhead, we resort
to QemuEvent. The caller of disabling will wait on QemuEvent of each
timerlist.
Note, qemu_clock_enable(foo,false) can _not_ be called from timer's cb.
Also, the callers of qemu_clock_enable() should be protected by the BQL.
Signed-off-by: Liu Ping Fan <address@hidden>
Signed-off-by: Paolo Bonzini <address@hidden>
---
include/qemu/timer.h | 6 ++++++
qemu-timer.c | 23 ++++++++++++++++++++++-
2 files changed, 28 insertions(+), 1 deletion(-)
diff --git a/include/qemu/timer.h b/include/qemu/timer.h
index 016e29a..1254ef7 100644
--- a/include/qemu/timer.h
+++ b/include/qemu/timer.h
@@ -189,6 +189,12 @@ void qemu_clock_notify(QEMUClockType type);
* @enabled: true to enable, false to disable
*
* Enable or disable a clock
+ * Disabling the clock will wait for related timerlists to stop
+ * executing qemu_run_timers. Thus, this functions should not
+ * be used from the callback of a timer that is based on @clock.
+ * Doing so would cause a deadlock.
+ *
+ * Caller should hold BQL.
*/
void qemu_clock_enable(QEMUClockType type, bool enabled);
diff --git a/qemu-timer.c b/qemu-timer.c
index 6b62e88..2b533da 100644
--- a/qemu-timer.c
+++ b/qemu-timer.c
@@ -45,6 +45,7 @@
/* timers */
typedef struct QEMUClock {
+ /* We rely on BQL to protect the timerlists */
QLIST_HEAD(, QEMUTimerList) timerlists;
NotifierList reset_notifiers;
@@ -71,6 +72,9 @@ struct QEMUTimerList {
QLIST_ENTRY(QEMUTimerList) list;
QEMUTimerListNotifyCB *notify_cb;
void *notify_opaque;
+
+ /* lightweight method to mark the end of timerlist's running */
+ QemuEvent timers_done_ev;
};
/**
@@ -99,6 +103,7 @@ QEMUTimerList *timerlist_new(QEMUClockType type,
QEMUClock *clock = qemu_clock_ptr(type);
timer_list = g_malloc0(sizeof(QEMUTimerList));
+ qemu_event_init(&timer_list->timers_done_ev, false);
timer_list->clock = clock;
timer_list->notify_cb = cb;
timer_list->notify_opaque = opaque;
@@ -143,13 +148,25 @@ void qemu_clock_notify(QEMUClockType type)
}
}
+/* Disabling the clock will wait for related timerlists to stop
+ * executing qemu_run_timers. Thus, this functions should not
+ * be used from the callback of a timer that is based on @clock.
+ * Doing so would cause a deadlock.
+ *
+ * Caller should hold BQL.
+ */
void qemu_clock_enable(QEMUClockType type, bool enabled)
{
QEMUClock *clock = qemu_clock_ptr(type);
+ QEMUTimerList *tl;
bool old = clock->enabled;
clock->enabled = enabled;
if (enabled && !old) {
qemu_clock_notify(type);
+ } else if (!enabled && old) {
+ QLIST_FOREACH(tl, &clock->timerlists, list) {
+ qemu_event_wait(&tl->timers_done_ev);
+ }
}
}
@@ -403,8 +420,9 @@ bool timerlist_run_timers(QEMUTimerList *timer_list)
QEMUTimerCB *cb;
void *opaque;
+ qemu_event_reset(&timer_list->timers_done_ev);
if (!timer_list->clock->enabled) {
- return progress;
+ goto out;
}
current_time = qemu_clock_get_ns(timer_list->clock->type);
@@ -428,6 +446,9 @@ bool timerlist_run_timers(QEMUTimerList *timer_list)
cb(opaque);
progress = true;
}
+
+out:
+ qemu_event_set(&timer_list->timers_done_ev);
return progress;
}
--
1.8.3.1
- [Qemu-devel] [PULL 02/17] compatfd: switch to QemuThread, (continued)
- [Qemu-devel] [PULL 02/17] compatfd: switch to QemuThread, Paolo Bonzini, 2013/10/17
- [Qemu-devel] [PULL 04/17] cirrus: Mark vga io region as coalesced MMIO flushing, Paolo Bonzini, 2013/10/17
- [Qemu-devel] [PULL 05/17] vga: Mark relevant portio lists regions as coalesced MMIO flushing, Paolo Bonzini, 2013/10/17
- [Qemu-devel] [PULL 03/17] portio: Allow to mark portio lists as coalesced MMIO flushing, Paolo Bonzini, 2013/10/17
- [Qemu-devel] [PULL 10/17] timer: extract timer_mod_ns_locked and timerlist_rearm, Paolo Bonzini, 2013/10/17
- [Qemu-devel] [PULL 11/17] timer: add timer_mod_anticipate and timer_mod_anticipate_ns, Paolo Bonzini, 2013/10/17
- [Qemu-devel] [PULL 07/17] timer: protect timers_state's clock with seqlock, Paolo Bonzini, 2013/10/17
- [Qemu-devel] [PULL 06/17] seqlock: introduce read-write seqlock, Paolo Bonzini, 2013/10/17
- [Qemu-devel] [PULL 08/17] qemu-thread: add QemuEvent, Paolo Bonzini, 2013/10/17
- [Qemu-devel] [PULL 12/17] icount: use cpu_get_icount() directly, Paolo Bonzini, 2013/10/17
- [Qemu-devel] [PULL 09/17] timer: make qemu_clock_enable sync between disable and timer's cb,
Paolo Bonzini <=
- [Qemu-devel] [PULL 15/17] icount: document (future) locking rules for icount, Paolo Bonzini, 2013/10/17
- [Qemu-devel] [PULL 13/17] icount: reorganize icount_warp_rt, Paolo Bonzini, 2013/10/17
- [Qemu-devel] [PULL 14/17] icount: prepare the code for future races in calling qemu_clock_warp, Paolo Bonzini, 2013/10/17
- [Qemu-devel] [PULL 16/17] icount: make it thread-safe, Paolo Bonzini, 2013/10/17
- [Qemu-devel] [PULL 17/17] exec: remove qemu_safe_ram_ptr, Paolo Bonzini, 2013/10/17