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[Qemu-devel] [PATCH v1 1/2] cpus: don't use atomic_read for vm_clock_war
From: |
Alex Bennée |
Subject: |
[Qemu-devel] [PATCH v1 1/2] cpus: don't use atomic_read for vm_clock_warp_start |
Date: |
Mon, 21 Mar 2016 16:23:05 +0000 |
As vm_clock_warp_start is a 64 bit value this causes problems for the
compiler trying to come up with a suitable atomic operation on 32 bit
hosts. The variable documentation says this is meant to be protected by
vm_clock_seqlock so lets just move the code into that section.
All other references to vm_clock_warp_start are already protected by the
seqlock.
Signed-off-by: Alex Bennée <address@hidden>
---
cpus.c | 12 ++++--------
1 file changed, 4 insertions(+), 8 deletions(-)
diff --git a/cpus.c b/cpus.c
index 23cf7aa..2fd5381 100644
--- a/cpus.c
+++ b/cpus.c
@@ -338,15 +338,10 @@ static int64_t qemu_icount_round(int64_t count)
static void icount_warp_rt(void)
{
- /* 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;
- }
+ bool check_clock = false;
seqlock_write_lock(&timers_state.vm_clock_seqlock);
- if (runstate_is_running()) {
+ if (vm_clock_warp_start != -1 && runstate_is_running()) {
int64_t clock = REPLAY_CLOCK(REPLAY_CLOCK_VIRTUAL_RT,
cpu_get_clock_locked());
int64_t warp_delta;
@@ -362,11 +357,12 @@ static void icount_warp_rt(void)
warp_delta = MIN(warp_delta, delta);
}
timers_state.qemu_icount_bias += warp_delta;
+ check_clock = true;
}
vm_clock_warp_start = -1;
seqlock_write_unlock(&timers_state.vm_clock_seqlock);
- if (qemu_clock_expired(QEMU_CLOCK_VIRTUAL)) {
+ if (check_clock && qemu_clock_expired(QEMU_CLOCK_VIRTUAL)) {
qemu_clock_notify(QEMU_CLOCK_VIRTUAL);
}
}
--
2.7.3