[Qemu-devel] [PATCH 02/18] block: access quiesce_counter with atomic ops

[Paolo Bonzini <pbonzini@redhat.com>]

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 block/io.c                | 4 ++--
 include/block/block_int.h | 1 +
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/block/io.c b/block/io.c
index a0de60acbc..3204e08c8f 100644
--- a/block/io.c
+++ b/block/io.c
@@ -241,7 +241,7 @@ void bdrv_drained_begin(BlockDriverState *bs)
         return;
     }
 
-    if (!bs->quiesce_counter++) {
+    if (atomic_fetch_inc(&bs->quiesce_counter) == 0) {
         aio_disable_external(bdrv_get_aio_context(bs));
         bdrv_parent_drained_begin(bs);
     }
@@ -252,7 +252,7 @@ void bdrv_drained_begin(BlockDriverState *bs)
 void bdrv_drained_end(BlockDriverState *bs)
 {
     assert(bs->quiesce_counter > 0);
-    if (--bs->quiesce_counter > 0) {
+    if (atomic_fetch_dec(&bs->quiesce_counter) > 1) {
         return;
     }
 
diff --git a/include/block/block_int.h b/include/block/block_int.h
index eb90c529cd..b529f894be 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -623,6 +623,7 @@ struct BlockDriverState {
     /* do we need to tell the quest if we have a volatile write cache? */
     int enable_write_cache;
 
+    /* Accessed with atomic ops.  */
     int quiesce_counter;
 };
 
-- 
2.12.2