From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:59728) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WrpW7-0001hN-3J for qemu-devel@nongnu.org; Tue, 03 Jun 2014 10:16:52 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1WrpVx-0002pT-Sj for qemu-devel@nongnu.org; Tue, 03 Jun 2014 10:16:43 -0400 Received: from mail-we0-x22d.google.com ([2a00:1450:400c:c03::22d]:63677) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WrpVx-0002pN-Lm for qemu-devel@nongnu.org; Tue, 03 Jun 2014 10:16:33 -0400 Received: by mail-we0-f173.google.com with SMTP id u57so6950404wes.32 for ; Tue, 03 Jun 2014 07:16:32 -0700 (PDT) Sender: Paolo Bonzini From: Paolo Bonzini Date: Tue, 3 Jun 2014 16:16:27 +0200 Message-Id: <1401804987-31085-1-git-send-email-pbonzini@redhat.com> Subject: [Qemu-devel] [PATCH] block: asynchronously stop the VM on I/O errors List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: kwolf@redhat.com, famz@redhat.com, stefanha@redhat.com With virtio-blk dataplane, I/O errors might occur while QEMU is not in the main I/O thread. However, it's invalid to call vm_stop when we're neither in a VCPU thread nor in the main I/O thread, even if we were to take the iothread mutex around it. To avoid this problem, simply raise a request to the main I/O thread, similar to what QEMU does when vm_stop is called from a CPU thread. We know that bdrv_error_action is called from an AIO callback, and the moment at which the callback will fire is not well-defined; it depends on the moment at which the disk or OS finishes the operation, which can happen at any time. Note that QEMU is certainly not in a CPU thread and we do not need to call cpu_stop_current() like vm_stop() does. This makes bdrv_error_action() thread safe. Signed-off-by: Paolo Bonzini --- block.c | 2 +- stubs/vm-stop.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/block.c b/block.c index fc2edd3..fa41598 100644 --- a/block.c +++ b/block.c @@ -3515,7 +3515,7 @@ void bdrv_error_action(BlockDriverState *bs, BlockErrorAction action, assert(error >= 0); bdrv_emit_qmp_error_event(bs, QEVENT_BLOCK_IO_ERROR, action, is_read); if (action == BDRV_ACTION_STOP) { - vm_stop(RUN_STATE_IO_ERROR); + qemu_system_vmstop_request(RUN_STATE_IO_ERROR); bdrv_iostatus_set_err(bs, error); } } diff --git a/stubs/vm-stop.c b/stubs/vm-stop.c index f82c897..7fbeefd 100644 --- a/stubs/vm-stop.c +++ b/stubs/vm-stop.c @@ -1,7 +1,7 @@ #include "qemu-common.h" #include "sysemu/sysemu.h" -int vm_stop(RunState state) +void qemu_system_vmstop_request(RunState state) { abort(); } -- 1.8.3.1