From 68265b080cec07c5a6ba6b1c6fbd867f4d9cf9ba Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Fri, 14 Sep 2018 10:55:34 +0200 Subject: [PATCH 43/49] block-backend: Decrease in_flight only after callback RH-Author: Kevin Wolf Message-id: <20180914105540.18077-37-kwolf@redhat.com> Patchwork-id: 82187 O-Subject: [RHV-7.6 qemu-kvm-rhev PATCH 36/42] block-backend: Decrease in_flight only after callback Bugzilla: 1601212 RH-Acked-by: John Snow RH-Acked-by: Max Reitz RH-Acked-by: Fam Zheng Request callbacks can do pretty much anything, including operations that will yield from the coroutine (such as draining the backend). In that case, a decreased in_flight would be visible to other code and could lead to a drain completing while the callback hasn't actually completed yet. Signed-off-by: Kevin Wolf Reviewed-by: Fam Zheng Reviewed-by: Max Reitz Signed-off-by: Miroslav Rezanina --- block/block-backend.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/block/block-backend.c b/block/block-backend.c index 1adf76b..466bc27 100644 --- a/block/block-backend.c +++ b/block/block-backend.c @@ -1341,8 +1341,16 @@ static const AIOCBInfo blk_aio_em_aiocb_info = { static void blk_aio_complete(BlkAioEmAIOCB *acb) { if (acb->has_returned) { - blk_dec_in_flight(acb->rwco.blk); + if (qemu_get_current_aio_context() == qemu_get_aio_context()) { + /* If we are in the main thread, the callback is allowed to unref + * the BlockBackend, so we have to hold an additional reference */ + blk_ref(acb->rwco.blk); + } acb->common.cb(acb->common.opaque, acb->rwco.ret); + blk_dec_in_flight(acb->rwco.blk); + if (qemu_get_current_aio_context() == qemu_get_aio_context()) { + blk_unref(acb->rwco.blk); + } qemu_aio_unref(acb); } } -- 1.8.3.1