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authorPaolo Bonzini <pbonzini@redhat.com>2013-10-28 17:32:18 +0100
committerAnthony Liguori <aliguori@amazon.com>2013-11-06 21:47:05 -0800
commit5f3e31012e334f3410e04abae7f88565df17c91a (patch)
tree75930e80e1a4fa885717c3528054d15cbda51704 /cpus.c
parentcd5be5829c1ce87aa6b3a7806524fac07ac9a757 (diff)
downloadqemu-arm-5f3e31012e334f3410e04abae7f88565df17c91a.tar.gz
timers: fix stop/cont with -icount
Stop/cont commands are broken with -icount due to a deadlock. The real problem is that the computation of timers_state.cpu_ticks_offset makes no sense with -icount enabled: we set it to an icount clock value in cpu_disable_ticks, and subtract a TSC (or similar, whatever cpu_get_real_ticks happens to return) value in cpu_enable_ticks. The fix is simple. timers_state.cpu_ticks_offset is only used together with cpu_get_real_ticks, so we can use cpu_get_real_ticks in cpu_disable_ticks. There is no need to update cpu_ticks_prev at the time cpu_disable_ticks is called; instead, we can do it the next time cpu_get_ticks is called. The change to cpu_disable_ticks is the important part of the patch. The rest modifies the code to always check timers_state.cpu_ticks_prev, even when the ticks are not advancing (i.e. the VM is stopped). It also makes a similar change to cpu_get_clock_locked, so that the code remains similar for cpu_get_ticks and cpu_get_clock_locked. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Message-id: 1382977938-13844-1-git-send-email-pbonzini@redhat.com Signed-off-by: Anthony Liguori <aliguori@amazon.com>
Diffstat (limited to 'cpus.c')
-rw-r--r--cpus.c42
1 files changed, 22 insertions, 20 deletions
diff --git a/cpus.c b/cpus.c
index 912938cd1b..01d128d7af 100644
--- a/cpus.c
+++ b/cpus.c
@@ -165,36 +165,38 @@ int64_t cpu_get_icount(void)
/* Caller must hold the BQL */
int64_t cpu_get_ticks(void)
{
+ int64_t ticks;
+
if (use_icount) {
return cpu_get_icount();
}
- if (!timers_state.cpu_ticks_enabled) {
- return timers_state.cpu_ticks_offset;
- } else {
- int64_t ticks;
- ticks = cpu_get_real_ticks();
- if (timers_state.cpu_ticks_prev > ticks) {
- /* Note: non increasing ticks may happen if the host uses
- software suspend */
- timers_state.cpu_ticks_offset += timers_state.cpu_ticks_prev - ticks;
- }
- timers_state.cpu_ticks_prev = ticks;
- return ticks + timers_state.cpu_ticks_offset;
+
+ ticks = timers_state.cpu_ticks_offset;
+ if (timers_state.cpu_ticks_enabled) {
+ ticks += cpu_get_real_ticks();
+ }
+
+ if (timers_state.cpu_ticks_prev > ticks) {
+ /* Note: non increasing ticks may happen if the host uses
+ software suspend */
+ timers_state.cpu_ticks_offset += timers_state.cpu_ticks_prev - ticks;
+ ticks = timers_state.cpu_ticks_prev;
}
+
+ timers_state.cpu_ticks_prev = ticks;
+ return ticks;
}
static int64_t cpu_get_clock_locked(void)
{
- int64_t ti;
+ int64_t ticks;
- if (!timers_state.cpu_ticks_enabled) {
- ti = timers_state.cpu_clock_offset;
- } else {
- ti = get_clock();
- ti += timers_state.cpu_clock_offset;
+ ticks = timers_state.cpu_clock_offset;
+ if (timers_state.cpu_ticks_enabled) {
+ ticks += get_clock();
}
- return ti;
+ return ticks;
}
/* return the host CPU monotonic timer and handle stop/restart */
@@ -235,7 +237,7 @@ void cpu_disable_ticks(void)
/* Here, the really thing protected by seqlock is cpu_clock_offset. */
seqlock_write_lock(&timers_state.vm_clock_seqlock);
if (timers_state.cpu_ticks_enabled) {
- timers_state.cpu_ticks_offset = cpu_get_ticks();
+ timers_state.cpu_ticks_offset += cpu_get_real_ticks();
timers_state.cpu_clock_offset = cpu_get_clock_locked();
timers_state.cpu_ticks_enabled = 0;
}