From 78c81a3f108870d325b0a39d88711366afe6f703 Mon Sep 17 00:00:00 2001 From: Max Reitz Date: Wed, 22 Jan 2020 17:45:28 +0100 Subject: [PATCH] block/nbd: Fix hang in .bdrv_close() When nbd_close() is called from a coroutine, the connection_co never gets to run, and thus nbd_teardown_connection() hangs. This is because aio_co_enter() only puts the connection_co into the main coroutine's wake-up queue, so this main coroutine needs to yield and wait for connection_co to terminate. Suggested-by: Kevin Wolf Signed-off-by: Max Reitz Message-Id: <20200122164532.178040-2-mreitz@redhat.com> Reviewed-by: Eric Blake Reviewed-by: Maxim Levitsky Signed-off-by: Max Reitz --- block/nbd.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) diff --git a/block/nbd.c b/block/nbd.c index d085554f21..6d3b22f844 100644 --- a/block/nbd.c +++ b/block/nbd.c @@ -70,6 +70,7 @@ typedef struct BDRVNBDState { CoMutex send_mutex; CoQueue free_sema; Coroutine *connection_co; + Coroutine *teardown_co; QemuCoSleepState *connection_co_sleep_ns_state; bool drained; bool wait_drained_end; @@ -203,7 +204,15 @@ static void nbd_teardown_connection(BlockDriverState *bs) qemu_co_sleep_wake(s->connection_co_sleep_ns_state); } } - BDRV_POLL_WHILE(bs, s->connection_co); + if (qemu_in_coroutine()) { + s->teardown_co = qemu_coroutine_self(); + /* connection_co resumes us when it terminates */ + qemu_coroutine_yield(); + s->teardown_co = NULL; + } else { + BDRV_POLL_WHILE(bs, s->connection_co); + } + assert(!s->connection_co); } static bool nbd_client_connecting(BDRVNBDState *s) @@ -395,6 +404,9 @@ static coroutine_fn void nbd_connection_entry(void *opaque) s->ioc = NULL; } + if (s->teardown_co) { + aio_co_wake(s->teardown_co); + } aio_wait_kick(); }