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icount: make it thread-safe

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This lets threads other than the I/O thread use vm_clock even in -icount mode.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2013-10-03 15:17:25 +02:00
parent a3270e19cc
commit 17a15f1b76
1 changed files with 31 additions and 6 deletions
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37
cpus.c
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@ -132,7 +132,7 @@ typedef struct TimersState {
static TimersState timers_state;
/* Return the virtual CPU time, based on the instruction counter. */
int64_t cpu_get_icount(void)
static int64_t cpu_get_icount_locked(void)
{
int64_t icount;
CPUState *cpu = current_cpu;
@ -148,6 +148,19 @@ int64_t cpu_get_icount(void)
return qemu_icount_bias + (icount << icount_time_shift);
}
int64_t cpu_get_icount(void)
{
int64_t icount;
unsigned start;
do {
start = seqlock_read_begin(&timers_state.vm_clock_seqlock);
icount = cpu_get_icount_locked();
} while (seqlock_read_retry(&timers_state.vm_clock_seqlock, start));
return icount;
}
/* return the host CPU cycle counter and handle stop/restart */
/* Caller must hold the BQL */
int64_t cpu_get_ticks(void)
@ -249,8 +262,9 @@ static void icount_adjust(void)
return;
}
cur_time = cpu_get_clock();
cur_icount = cpu_get_icount();
seqlock_write_lock(&timers_state.vm_clock_seqlock);
cur_time = cpu_get_clock_locked();
cur_icount = cpu_get_icount_locked();
delta = cur_icount - cur_time;
/* FIXME: This is a very crude algorithm, somewhat prone to oscillation. */
@ -268,6 +282,7 @@ static void icount_adjust(void)
}
last_delta = delta;
qemu_icount_bias = cur_icount - (qemu_icount << icount_time_shift);
seqlock_write_unlock(&timers_state.vm_clock_seqlock);
}
static void icount_adjust_rt(void *opaque)
@ -292,10 +307,14 @@ static int64_t qemu_icount_round(int64_t count)
static void icount_warp_rt(void *opaque)
{
if (vm_clock_warp_start == -1) {
/* The icount_warp_timer is rescheduled soon after vm_clock_warp_start
* changes from -1 to another value, so the race here is okay.
*/
if (atomic_read(&vm_clock_warp_start) == -1) {
return;
}
seqlock_write_lock(&timers_state.vm_clock_seqlock);
if (runstate_is_running()) {
int64_t clock = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
int64_t warp_delta;
@ -306,14 +325,15 @@ static void icount_warp_rt(void *opaque)
* In adaptive mode, do not let QEMU_CLOCK_VIRTUAL run too
* far ahead of real time.
*/
int64_t cur_time = cpu_get_clock();
int64_t cur_icount = cpu_get_icount();
int64_t cur_time = cpu_get_clock_locked();
int64_t cur_icount = cpu_get_icount_locked();
int64_t delta = cur_time - cur_icount;
warp_delta = MIN(warp_delta, delta);
}
qemu_icount_bias += warp_delta;
}
vm_clock_warp_start = -1;
seqlock_write_unlock(&timers_state.vm_clock_seqlock);
if (qemu_clock_expired(QEMU_CLOCK_VIRTUAL)) {
qemu_clock_notify(QEMU_CLOCK_VIRTUAL);
@ -327,7 +347,10 @@ void qtest_clock_warp(int64_t dest)
while (clock < dest) {
int64_t deadline = qemu_clock_deadline_ns_all(QEMU_CLOCK_VIRTUAL);
int64_t warp = MIN(dest - clock, deadline);
seqlock_write_lock(&timers_state.vm_clock_seqlock);
qemu_icount_bias += warp;
seqlock_write_unlock(&timers_state.vm_clock_seqlock);
qemu_clock_run_timers(QEMU_CLOCK_VIRTUAL);
clock = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
}
@ -391,9 +414,11 @@ void qemu_clock_warp(QEMUClockType type)
* you will not be sending network packets continuously instead of
* every 100ms.
*/
seqlock_write_lock(&timers_state.vm_clock_seqlock);
if (vm_clock_warp_start == -1 || vm_clock_warp_start > clock) {
vm_clock_warp_start = clock;
}
seqlock_write_unlock(&timers_state.vm_clock_seqlock);
timer_mod_anticipate(icount_warp_timer, clock + deadline);
} else if (deadline == 0) {
qemu_clock_notify(QEMU_CLOCK_VIRTUAL);