qcow2: Take locks for accessing bs->file

[mirror_qemu.git] / block / graph-lock.c

diff --git a/block/graph-lock.c b/block/graph-lock.c
index f357a2c0b17031f111f77fd813880fe67dc61eb2..e5525ee2db4474c70a68a70be81edd2efa23d0c6 100644 (file)
--- a/block/graph-lock.c
+++ b/block/graph-lock.c
@@ -106,12 +106,13 @@ static uint32_t reader_count(void)
     return rd;
 }
 
-void bdrv_graph_wrlock(BlockDriverState *bs)
+void no_coroutine_fn bdrv_graph_wrlock(BlockDriverState *bs)
 {
     AioContext *ctx = NULL;
 
     GLOBAL_STATE_CODE();
     assert(!qatomic_read(&has_writer));
+    assert(!qemu_in_coroutine());
 
     /*
      * Release only non-mainloop AioContext. The mainloop often relies on the
@@ -163,17 +164,29 @@ void bdrv_graph_wrlock(BlockDriverState *bs)
 void bdrv_graph_wrunlock(void)
 {
     GLOBAL_STATE_CODE();
-    QEMU_LOCK_GUARD(&aio_context_list_lock);
     assert(qatomic_read(&has_writer));
 
+    WITH_QEMU_LOCK_GUARD(&aio_context_list_lock) {
+        /*
+         * No need for memory barriers, this works in pair with
+         * the slow path of rdlock() and both take the lock.
+         */
+        qatomic_store_release(&has_writer, 0);
+
+        /* Wake up all coroutines that are waiting to read the graph */
+        qemu_co_enter_all(&reader_queue, &aio_context_list_lock);
+    }
+
     /*
-     * No need for memory barriers, this works in pair with
-     * the slow path of rdlock() and both take the lock.
+     * Run any BHs that were scheduled during the wrlock section and that
+     * callers might expect to have finished (in particular, this is important
+     * for bdrv_schedule_unref()).
+     *
+     * Do this only after restarting coroutines so that nested event loops in
+     * BHs don't deadlock if their condition relies on the coroutine making
+     * progress.
      */
-    qatomic_store_release(&has_writer, 0);
-
-    /* Wake up all coroutine that are waiting to read the graph */
-    qemu_co_enter_all(&reader_queue, &aio_context_list_lock);
+    aio_bh_poll(qemu_get_aio_context());
 }
 
 void coroutine_fn bdrv_graph_co_rdlock(void)