From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:59531) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dcZrT-0004Iz-Q0 for qemu-devel@nongnu.org; Tue, 01 Aug 2017 12:17:37 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dcZrR-00079p-Rt for qemu-devel@nongnu.org; Tue, 01 Aug 2017 12:17:35 -0400 Received: from mail-wr0-x242.google.com ([2a00:1450:400c:c0c::242]:35344) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1dcZrR-00078v-LB for qemu-devel@nongnu.org; Tue, 01 Aug 2017 12:17:33 -0400 Received: by mail-wr0-x242.google.com with SMTP id c24so1805028wra.2 for ; Tue, 01 Aug 2017 09:17:32 -0700 (PDT) Sender: Paolo Bonzini From: Paolo Bonzini Date: Tue, 1 Aug 2017 18:17:09 +0200 Message-Id: <1501604245-33460-2-git-send-email-pbonzini@redhat.com> In-Reply-To: <1501604245-33460-1-git-send-email-pbonzini@redhat.com> References: <1501604245-33460-1-git-send-email-pbonzini@redhat.com> Subject: [Qemu-devel] [PULL 01/17] vl.c/exit: pause cpus before closing block devices List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: "Dr. David Alan Gilbert" From: "Dr. David Alan Gilbert" There's a rare exit seg if the guest is accessing IO during exit. It's always hitting the atomic_inc(&bs->in_flight) with a NULL bs. This was added recently in 99723548 but I don't see it as the cause. Flip vl.c around so we pause the cpus before closing the block devices, that way we shouldn't have anything trying to access them when they're gone. This was originally Red Hat bz https://bugzilla.redhat.com/show_bug.cgi?id=1451015 Signed-off-by: Dr. David Alan Gilbert Reported-by: Cong Li -- This is a very rare race, I'll leave it running in a loop to see if we hit anything else and to check this really fixes it. I do worry if there are other cases that can trigger this - e.g. hot-unplug or ejecting a CD. Message-Id: <20170713190116.21608-1-dgilbert@redhat.com> Signed-off-by: Paolo Bonzini --- vl.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/vl.c b/vl.c index fb6b2ef..dd803fc 100644 --- a/vl.c +++ b/vl.c @@ -4787,8 +4787,8 @@ int main(int argc, char **argv, char **envp) replay_disable_events(); iothread_stop_all(); - bdrv_close_all(); pause_all_vcpus(); + bdrv_close_all(); res_free(); /* vhost-user must be cleaned up before chardevs. */ -- 1.8.3.1