1 files changed, 19 insertions, 24 deletions

diff --git a/block/graph-lock.c b/block/graph-lock.c
index a92c6ae219..5e66f01ae8 100644
--- a/block/graph-lock.c
+++ b/block/graph-lock.c
@@ -30,10 +30,8 @@ BdrvGraphLock graph_lock;
 /* Protects the list of aiocontext and orphaned_reader_count */
 static QemuMutex aio_context_list_lock;
 
-#if 0
 /* Written and read with atomic operations. */
 static int has_writer;
-#endif
 
 /*
  * A reader coroutine could move from an AioContext to another.
@@ -90,7 +88,6 @@ void unregister_aiocontext(AioContext *ctx)
     g_free(ctx->bdrv_graph);
 }
 
-#if 0
 static uint32_t reader_count(void)
 {
     BdrvGraphRWlock *brdv_graph;
@@ -108,18 +105,26 @@ static uint32_t reader_count(void)
     assert((int32_t)rd >= 0);
     return rd;
 }
-#endif
 
-void bdrv_graph_wrlock(void)
+void bdrv_graph_wrlock(BlockDriverState *bs)
 {
+    AioContext *ctx = NULL;
+
     GLOBAL_STATE_CODE();
+    assert(!qatomic_read(&has_writer));
+
     /*
-     * TODO Some callers hold an AioContext lock when this is called, which
-     * causes deadlocks. Reenable once the AioContext locking is cleaned up (or
-     * AioContext locks are gone).
+     * Release only non-mainloop AioContext. The mainloop often relies on the
+     * BQL and doesn't lock the main AioContext before doing things.
      */
-#if 0
-    assert(!qatomic_read(&has_writer));
+    if (bs) {
+        ctx = bdrv_get_aio_context(bs);
+        if (ctx != qemu_get_aio_context()) {
+            aio_context_release(ctx);
+        } else {
+            ctx = NULL;
+        }
+    }
 
     /* Make sure that constantly arriving new I/O doesn't cause starvation */
     bdrv_drain_all_begin_nopoll();
@@ -149,13 +154,15 @@ void bdrv_graph_wrlock(void)
     } while (reader_count() >= 1);
 
     bdrv_drain_all_end();
-#endif
+
+    if (ctx) {
+        aio_context_acquire(bdrv_get_aio_context(bs));
+    }
 }
 
 void bdrv_graph_wrunlock(void)
 {
     GLOBAL_STATE_CODE();
-#if 0
     QEMU_LOCK_GUARD(&aio_context_list_lock);
     assert(qatomic_read(&has_writer));
 
@@ -167,13 +174,10 @@ void bdrv_graph_wrunlock(void)
 
     /* Wake up all coroutine that are waiting to read the graph */
     qemu_co_enter_all(&reader_queue, &aio_context_list_lock);
-#endif
 }
 
 void coroutine_fn bdrv_graph_co_rdlock(void)
 {
-    /* TODO Reenable when wrlock is reenabled */
-#if 0
     BdrvGraphRWlock *bdrv_graph;
     bdrv_graph = qemu_get_current_aio_context()->bdrv_graph;
 
@@ -233,12 +237,10 @@ void coroutine_fn bdrv_graph_co_rdlock(void)
             qemu_co_queue_wait(&reader_queue, &aio_context_list_lock);
         }
     }
-#endif
 }
 
 void coroutine_fn bdrv_graph_co_rdunlock(void)
 {
-#if 0
     BdrvGraphRWlock *bdrv_graph;
     bdrv_graph = qemu_get_current_aio_context()->bdrv_graph;
 
@@ -256,7 +258,6 @@ void coroutine_fn bdrv_graph_co_rdunlock(void)
     if (qatomic_read(&has_writer)) {
         aio_wait_kick();
     }
-#endif
 }
 
 void bdrv_graph_rdlock_main_loop(void)
@@ -274,19 +275,13 @@ void bdrv_graph_rdunlock_main_loop(void)
 void assert_bdrv_graph_readable(void)
 {
     /* reader_count() is slow due to aio_context_list_lock lock contention */
-    /* TODO Reenable when wrlock is reenabled */
-#if 0
 #ifdef CONFIG_DEBUG_GRAPH_LOCK
     assert(qemu_in_main_thread() || reader_count());
 #endif
-#endif
 }
 
 void assert_bdrv_graph_writable(void)
 {
     assert(qemu_in_main_thread());
-    /* TODO Reenable when wrlock is reenabled */
-#if 0
     assert(qatomic_read(&has_writer));
-#endif
 }