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[Qemu-devel] [RFC 4/8] timer: protect timers_state with lock
From: |
Liu Ping Fan |
Subject: |
[Qemu-devel] [RFC 4/8] timer: protect timers_state with lock |
Date: |
Sun, 21 Jul 2013 16:43:01 +0800 |
In kvm mode, vm_clock may be read on AioContexts outside BQL(next
patch). This will make timers_state --the foundation of vm_clock
exposed to race condition. Using private lock to protect it.
Note in tcg mode, vm_clock still read inside BQL, so icount is
left without change.
Lock rule: private lock innermost, ie BQL->"this lock"
Signed-off-by: Liu Ping Fan <address@hidden>
---
cpus.c | 27 +++++++++++++++++++++++----
1 file changed, 23 insertions(+), 4 deletions(-)
diff --git a/cpus.c b/cpus.c
index 4254ca9..22df5fb 100644
--- a/cpus.c
+++ b/cpus.c
@@ -113,6 +113,8 @@ typedef struct TimersState {
} TimersState;
static TimersState timers_state;
+/* lock rule: innermost */
+static QemuMutex timers_state_lock;
/* Return the virtual CPU time, based on the instruction counter. */
int64_t cpu_get_icount(void)
@@ -134,11 +136,15 @@ int64_t cpu_get_icount(void)
/* return the host CPU cycle counter and handle stop/restart */
int64_t cpu_get_ticks(void)
{
+ int64_t ret;
+
if (use_icount) {
return cpu_get_icount();
}
+ qemu_mutex_lock(&timers_state_lock);
if (!timers_state.cpu_ticks_enabled) {
- return timers_state.cpu_ticks_offset;
+ ret = timers_state.cpu_ticks_offset;
+ goto out;
} else {
int64_t ticks;
ticks = cpu_get_real_ticks();
@@ -148,41 +154,53 @@ int64_t cpu_get_ticks(void)
timers_state.cpu_ticks_offset += timers_state.cpu_ticks_prev -
ticks;
}
timers_state.cpu_ticks_prev = ticks;
- return ticks + timers_state.cpu_ticks_offset;
+ ret = ticks + timers_state.cpu_ticks_offset;
+ goto out;
}
+out:
+ qemu_mutex_lock(&timers_state_lock);
+ return ret;
}
/* return the host CPU monotonic timer and handle stop/restart */
int64_t cpu_get_clock(void)
{
int64_t ti;
+
+ qemu_mutex_lock(&timers_state_lock);
if (!timers_state.cpu_ticks_enabled) {
- return timers_state.cpu_clock_offset;
+ ti = timers_state.cpu_clock_offset;
} else {
ti = get_clock();
- return ti + timers_state.cpu_clock_offset;
+ ti += timers_state.cpu_clock_offset;
}
+ qemu_mutex_unlock(&timers_state_lock);
+ return ti;
}
/* enable cpu_get_ticks() */
void cpu_enable_ticks(void)
{
+ qemu_mutex_lock(&timers_state_lock);
if (!timers_state.cpu_ticks_enabled) {
timers_state.cpu_ticks_offset -= cpu_get_real_ticks();
timers_state.cpu_clock_offset -= get_clock();
timers_state.cpu_ticks_enabled = 1;
}
+ qemu_mutex_unlock(&timers_state_lock);
}
/* disable cpu_get_ticks() : the clock is stopped. You must not call
cpu_get_ticks() after that. */
void cpu_disable_ticks(void)
{
+ qemu_mutex_lock(&timers_state_lock);
if (timers_state.cpu_ticks_enabled) {
timers_state.cpu_ticks_offset = cpu_get_ticks();
timers_state.cpu_clock_offset = cpu_get_clock();
timers_state.cpu_ticks_enabled = 0;
}
+ qemu_mutex_unlock(&timers_state_lock);
}
/* Correlation between real and virtual time is always going to be
@@ -353,6 +371,7 @@ static const VMStateDescription vmstate_timers = {
void configure_icount(const char *option)
{
+ qemu_mutex_init(&timers_state_lock);
vmstate_register(NULL, 0, &vmstate_timers, &timers_state);
if (!option) {
return;
--
1.8.1.4
- [Qemu-devel] [RFC 0/8] arm AioContext with its own timer stuff, Liu Ping Fan, 2013/07/21
- [Qemu-devel] [RFC 1/8] timer: associate alarm_timer with AioContext, Liu Ping Fan, 2013/07/21
- [Qemu-devel] [RFC 2/8] timer: pick out timer list info from QemuClock, Liu Ping Fan, 2013/07/21
- [Qemu-devel] [RFC 3/8] timer: make timers_state static, Liu Ping Fan, 2013/07/21
- [Qemu-devel] [RFC 4/8] timer: protect timers_state with lock,
Liu Ping Fan <=
- [Qemu-devel] [RFC 5/8] timer: associate timer with AioContext, Liu Ping Fan, 2013/07/21
- [Qemu-devel] [RFC 6/8] timer: run timers on aio_poll, Liu Ping Fan, 2013/07/21
- [Qemu-devel] [RFC 7/8] block: associate BlockDriverState with AioContext, Liu Ping Fan, 2013/07/21
- [Qemu-devel] [RFC 8/8] block: enable throttle with aiocontext, Liu Ping Fan, 2013/07/21
- Re: [Qemu-devel] [RFC 0/8] arm AioContext with its own timer stuff, Alex Bligh, 2013/07/21