diff options
| -rw-r--r-- | block.c | 4 | ||||
| -rw-r--r-- | block/graph-lock.c | 23 | ||||
| -rw-r--r-- | include/block/graph-lock.h | 6 |
3 files changed, 28 insertions, 5 deletions
@@ -2854,7 +2854,7 @@ uint64_t bdrv_qapi_perm_to_blk_perm(BlockPermission qapi_perm) * Replaces the node that a BdrvChild points to without updating permissions. * * If @new_bs is non-NULL, the parent of @child must already be drained through - * @child. + * @child and the caller must hold the AioContext lock for @new_bs. */ static void bdrv_replace_child_noperm(BdrvChild *child, BlockDriverState *new_bs) @@ -2893,7 +2893,7 @@ static void bdrv_replace_child_noperm(BdrvChild *child, } /* TODO Pull this up into the callers to avoid polling here */ - bdrv_graph_wrlock(); + bdrv_graph_wrlock(new_bs); if (old_bs) { if (child->klass->detach) { child->klass->detach(child); diff --git a/block/graph-lock.c b/block/graph-lock.c index a92c6ae219..3bf2591dc4 100644 --- a/block/graph-lock.c +++ b/block/graph-lock.c @@ -110,8 +110,10 @@ static uint32_t reader_count(void) } #endif -void bdrv_graph_wrlock(void) +void bdrv_graph_wrlock(BlockDriverState *bs) { + AioContext *ctx = NULL; + GLOBAL_STATE_CODE(); /* * TODO Some callers hold an AioContext lock when this is called, which @@ -120,7 +122,22 @@ void bdrv_graph_wrlock(void) */ #if 0 assert(!qatomic_read(&has_writer)); +#endif + + /* + * Release only non-mainloop AioContext. The mainloop often relies on the + * BQL and doesn't lock the main AioContext before doing things. + */ + if (bs) { + ctx = bdrv_get_aio_context(bs); + if (ctx != qemu_get_aio_context()) { + aio_context_release(ctx); + } else { + ctx = NULL; + } + } +#if 0 /* Make sure that constantly arriving new I/O doesn't cause starvation */ bdrv_drain_all_begin_nopoll(); @@ -150,6 +167,10 @@ void bdrv_graph_wrlock(void) bdrv_drain_all_end(); #endif + + if (ctx) { + aio_context_acquire(bdrv_get_aio_context(bs)); + } } void bdrv_graph_wrunlock(void) diff --git a/include/block/graph-lock.h b/include/block/graph-lock.h index 7574a2de5b..7e04f98ff0 100644 --- a/include/block/graph-lock.h +++ b/include/block/graph-lock.h @@ -111,10 +111,12 @@ void unregister_aiocontext(AioContext *ctx); * The wrlock can only be taken from the main loop, with BQL held, as only the * main loop is allowed to modify the graph. * + * If @bs is non-NULL, its AioContext is temporarily released. + * * This function polls. Callers must not hold the lock of any AioContext other - * than the current one. + * than the current one and the one of @bs. */ -void bdrv_graph_wrlock(void) TSA_ACQUIRE(graph_lock) TSA_NO_TSA; +void bdrv_graph_wrlock(BlockDriverState *bs) TSA_ACQUIRE(graph_lock) TSA_NO_TSA; /* * bdrv_graph_wrunlock: |