On Mon, Sep 23, 2013 at 2:26 PM, Jan Kiszka <jan.kis...@siemens.com> wrote:
> On 2013-09-22 10:11, Liu Ping Fan wrote:
>> 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.
>> And the callers of qemu_clock_enable() should be sync by themselves,
>> not protected by this patch.
>>
>> Signed-off-by: Liu Ping Fan <pingf...@linux.vnet.ibm.com>
>> ---
>> include/qemu/timer.h | 4 ++++
>> qemu-timer.c | 20 +++++++++++++++++++-
>> 2 files changed, 23 insertions(+), 1 deletion(-)
>>
>> diff --git a/include/qemu/timer.h b/include/qemu/timer.h
>> index e4934dd..b26909a 100644
>> --- a/include/qemu/timer.h
>> +++ b/include/qemu/timer.h
>> @@ -185,6 +185,10 @@ 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.
>> */
>> void qemu_clock_enable(QEMUClockType type, bool enabled);
>>
>> diff --git a/qemu-timer.c b/qemu-timer.c
>> index 95ff47f..c500a76 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;
>> @@ -70,6 +71,8 @@ struct QEMUTimerList {
>> QLIST_ENTRY(QEMUTimerList) list;
>> QEMUTimerListNotifyCB *notify_cb;
>> void *notify_opaque;
>> + /* light weight method to mark the end of timerlist's running */
>> + QemuEvent ev;
>
> What about "timers_done_ev"?
>
fine, thx.
>> };
>>
>> /**
>> @@ -98,6 +101,7 @@ QEMUTimerList *timerlist_new(QEMUClockType type,
>> QEMUClock *clock = qemu_clock_ptr(type);
>>
>> timer_list = g_malloc0(sizeof(QEMUTimerList));
>> + qemu_event_init(&timer_list->ev, false);
>> timer_list->clock = clock;
>> timer_list->notify_cb = cb;
>> timer_list->notify_opaque = opaque;
>> @@ -140,13 +144,24 @@ 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.
>> + */
>> 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) {
>> + /* We rely on BQL to protect the timerlists */
>
> So the caller of qemu_clock_enable has to hold the BQL? Then please add
> that to the function description above instead.
>
Ok, thx.
Regards,
Pingfan
>> + QLIST_FOREACH(tl, &clock->timerlists, list) {
>> + qemu_event_wait(&tl->ev);
>> + }
>> }
>> }
>>
>> @@ -373,8 +388,10 @@ bool timerlist_run_timers(QEMUTimerList *timer_list)
>> QEMUTimer *ts;
>> int64_t current_time;
>> bool progress = false;
>> -
>> +
>> + qemu_event_reset(&timer_list->ev);
>> if (!timer_list->clock->enabled) {
>> + qemu_event_set(&timer_list->ev);
>> return progress;
>> }
>>
>> @@ -392,6 +409,7 @@ bool timerlist_run_timers(QEMUTimerList *timer_list)
>> ts->cb(ts->opaque);
>> progress = true;
>> }
>> + qemu_event_set(&timer_list->ev);
>> return progress;
>> }
>>
>>
>
>
> --
> Siemens AG, Corporate Technology, CT RTC ITP SES-DE
> Corporate Competence Center Embedded Linux
