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authorJan Kiszka <jan.kiszka@siemens.com>2011-06-20 14:06:27 +0200
committerAnthony Liguori <aliguori@us.ibm.com>2011-07-23 11:26:12 -0500
commit691a0c9c9b71360271220c12f20a7238bc302503 (patch)
treedd73ff536345dad4741b6fab3ccd4112d9fe8215 /qemu-timer.c
parent9e8dd45164af05a5dab00324dd10b037f5bd1e2a (diff)
downloadqemu-arm-691a0c9c9b71360271220c12f20a7238bc302503.tar.gz
qemu-timer: Introduce clock reset notifier
QEMU_CLOCK_HOST is based on the system time which may jump backward in case the admin or NTP adjusts it. RTC emulations and other device models can suffer in this case as timers will stall for the period the clock was tuned back. This adds a detection mechanism that checks on every host clock readout if the new time is before the last result. If that is the case a notifier list is informed. Device models interested in this event can register a notifier with the clock. Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com> Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Diffstat (limited to 'qemu-timer.c')
-rw-r--r--qemu-timer.c29
1 files changed, 28 insertions, 1 deletions
diff --git a/qemu-timer.c b/qemu-timer.c
index 67c2974959..f95374c7c1 100644
--- a/qemu-timer.c
+++ b/qemu-timer.c
@@ -150,6 +150,9 @@ struct QEMUClock {
int enabled;
QEMUTimer *warp_timer;
+
+ NotifierList reset_notifiers;
+ int64_t last;
};
struct QEMUTimer {
@@ -376,9 +379,15 @@ static QEMUTimer *active_timers[QEMU_NUM_CLOCKS];
static QEMUClock *qemu_new_clock(int type)
{
QEMUClock *clock;
+
clock = qemu_mallocz(sizeof(QEMUClock));
clock->type = type;
clock->enabled = 1;
+ notifier_list_init(&clock->reset_notifiers);
+ /* required to detect & report backward jumps */
+ if (type == QEMU_CLOCK_HOST) {
+ clock->last = get_clock_realtime();
+ }
return clock;
}
@@ -593,6 +602,8 @@ static void qemu_run_timers(QEMUClock *clock)
int64_t qemu_get_clock_ns(QEMUClock *clock)
{
+ int64_t now, last;
+
switch(clock->type) {
case QEMU_CLOCK_REALTIME:
return get_clock();
@@ -604,10 +615,26 @@ int64_t qemu_get_clock_ns(QEMUClock *clock)
return cpu_get_clock();
}
case QEMU_CLOCK_HOST:
- return get_clock_realtime();
+ now = get_clock_realtime();
+ last = clock->last;
+ clock->last = now;
+ if (now < last) {
+ notifier_list_notify(&clock->reset_notifiers, &now);
+ }
+ return now;
}
}
+void qemu_register_clock_reset_notifier(QEMUClock *clock, Notifier *notifier)
+{
+ notifier_list_add(&clock->reset_notifiers, notifier);
+}
+
+void qemu_unregister_clock_reset_notifier(QEMUClock *clock, Notifier *notifier)
+{
+ notifier_list_remove(&clock->reset_notifiers, notifier);
+}
+
void init_clocks(void)
{
rt_clock = qemu_new_clock(QEMU_CLOCK_REALTIME);