From: Xiao Guangrong <xiaoguangr...@tencent.com>
Try to hold src_page_req_mutex only if the queue is not
empty
Reviewed-by: Dr. David Alan Gilbert <dgilb...@redhat.com>
Signed-off-by: Xiao Guangrong <xiaoguangr...@tencent.com>
---
include/qemu/queue.h | 1 +
migration/ram.c | 4 ++++
2 files changed, 5 insertions(+)
diff --git a/include/qemu/queue.h b/include/qemu/queue.h
index 59fd1203a1..ac418efc43 100644
--- a/include/qemu/queue.h
+++ b/include/qemu/queue.h
@@ -341,6 +341,7 @@ struct {
\
/*
* Simple queue access methods.
*/
+#define QSIMPLEQ_EMPTY_ATOMIC(head) (atomic_read(&((head)->sqh_first)) == NULL)
#define QSIMPLEQ_EMPTY(head) ((head)->sqh_first == NULL)
#define QSIMPLEQ_FIRST(head) ((head)->sqh_first)
#define QSIMPLEQ_NEXT(elm, field) ((elm)->field.sqe_next)
diff --git a/migration/ram.c b/migration/ram.c
index e1909502da..89305c7af5 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -2062,6 +2062,10 @@ static RAMBlock *unqueue_page(RAMState *rs, ram_addr_t
*offset)
{
RAMBlock *block = NULL;
+ if (QSIMPLEQ_EMPTY_ATOMIC(&rs->src_page_requests)) {
+ return NULL;
+ }
+
qemu_mutex_lock(&rs->src_page_req_mutex);
if (!QSIMPLEQ_EMPTY(&rs->src_page_requests)) {
struct RAMSrcPageRequest *entry =
--
2.14.4
