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authorKevin Wolf <kwolf@redhat.com>2020-10-05 17:58:54 +0200
committerMarkus Armbruster <armbru@redhat.com>2020-10-09 07:08:20 +0200
commit18c6ac1c6eb7cc541249585836659d0d3ed3a539 (patch)
tree7a923644454f1b0a4c395a8a6673d453ec33f0b0 /block.c
parente336fd4c4b2fa04e5d6c7f8ee524bfd2d9e9e8f1 (diff)
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block: Add bdrv_lock()/unlock()
Inside of coroutine context, we can't directly use aio_context_acquire() for the AioContext of a block node because we already own the lock of the current AioContext and we need to avoid double locking to prevent deadlocks. This provides helper functions to lock the AioContext of a node only if it's not the same as the current AioContext. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Message-Id: <20201005155855.256490-14-kwolf@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Markus Armbruster <armbru@redhat.com>
Diffstat (limited to 'block.c')
-rw-r--r--block.c27
1 files changed, 27 insertions, 0 deletions
diff --git a/block.c b/block.c
index 8d9b901..430edf7 100644
--- a/block.c
+++ b/block.c
@@ -6326,6 +6326,33 @@ void coroutine_fn bdrv_co_leave(BlockDriverState *bs, AioContext *old_ctx)
bdrv_dec_in_flight(bs);
}
+void coroutine_fn bdrv_co_lock(BlockDriverState *bs)
+{
+ AioContext *ctx = bdrv_get_aio_context(bs);
+
+ /* In the main thread, bs->aio_context won't change concurrently */
+ assert(qemu_get_current_aio_context() == qemu_get_aio_context());
+
+ /*
+ * We're in coroutine context, so we already hold the lock of the main
+ * loop AioContext. Don't lock it twice to avoid deadlocks.
+ */
+ assert(qemu_in_coroutine());
+ if (ctx != qemu_get_aio_context()) {
+ aio_context_acquire(ctx);
+ }
+}
+
+void coroutine_fn bdrv_co_unlock(BlockDriverState *bs)
+{
+ AioContext *ctx = bdrv_get_aio_context(bs);
+
+ assert(qemu_in_coroutine());
+ if (ctx != qemu_get_aio_context()) {
+ aio_context_release(ctx);
+ }
+}
+
void bdrv_coroutine_enter(BlockDriverState *bs, Coroutine *co)
{
aio_co_enter(bdrv_get_aio_context(bs), co);