On 04/15/10 01:08, Paolo Bonzini wrote:
On 04/14/2010 06:52 PM, Blue Swirl wrote:
On 4/14/10, Gerd Hoffmann<kra...@redhat.com> wrote:
+static inline void atomic_or(uint32_t *var, uint32_t add)
+{
+ __asm__ __volatile__ ("lock; orl %1, %0" : "+m" (*var) : "r" (add)
: "memory");
+}
This will break on non-x86 hosts.
I'd just use __sync_fetch_and_or here.
Good idea. I think we can zap the memory barrier and fix a small race
while being at it, see the incremental fix below.
cheers,
Gerd
diff --git a/hw/qxl.c b/hw/qxl.c
index 7ac06f6..8cbd9a3 100644
--- a/hw/qxl.c
+++ b/hw/qxl.c
@@ -6,7 +6,6 @@
#include <pthread.h>
#include "qemu-common.h"
-#include "qemu-barrier.h"
#include "qemu-spice.h"
#include "qemu-timer.h"
#include "qemu-queue.h"
@@ -176,11 +175,6 @@ static inline uint32_t msb_mask(uint32_t val)
return mask;
}
-static inline void atomic_or(uint32_t *var, uint32_t add)
-{
- __asm__ __volatile__ ("lock; orl %1, %0" : "+m" (*var) : "r" (add) :
"memory");
-}
-
static ram_addr_t qxl_rom_size(void)
{
uint32_t rom_size = sizeof(QXLRom) + sizeof(QXLModes) + sizeof(qxl_modes);
@@ -892,12 +886,13 @@ static void pipe_read(void *opaque)
static void qxl_send_events(PCIQXLDevice *d, uint32_t events)
{
+ uint32_t old_pending;
+
assert(d->ssd.running);
- smp_wmb();
- if ((d->ram->int_pending & events) == events) {
+ old_pending = __sync_fetch_and_or(&d->ram->int_pending, events);
+ if ((old_pending & events) == events) {
return;
}
- atomic_or(&d->ram->int_pending, events);
if (pthread_self() == d->main) {
qxl_set_irq(d);
} else {
