| Message ID | 20180907161520.26349-11-kwolf@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Fix some jobs/drain/aio_poll related hangs | expand |
On Fri, 09/07 18:15, Kevin Wolf wrote: > 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 <kwolf@redhat.com> Reviewed-by: Fam Zheng <famz@redhat.com>
diff --git a/block/block-backend.c b/block/block-backend.c index 1b2d7a6ff5..2efaf0c968 100644 --- a/block/block-backend.c +++ b/block/block-backend.c @@ -1338,8 +1338,16 @@ 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); } }
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 <kwolf@redhat.com> --- block/block-backend.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-)