From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:36669) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aIzlf-0004kH-Gg for qemu-devel@nongnu.org; Tue, 12 Jan 2016 09:17:54 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1aIzlV-0004AU-QE for qemu-devel@nongnu.org; Tue, 12 Jan 2016 09:17:51 -0500 Received: from mx1.redhat.com ([209.132.183.28]:55987) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aIzlV-0004AQ-Ko for qemu-devel@nongnu.org; Tue, 12 Jan 2016 09:17:41 -0500 Message-ID: <1452608259.29014.26.camel@redhat.com> From: Gerd Hoffmann Date: Tue, 12 Jan 2016 15:17:39 +0100 In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Mime-Version: 1.0 Subject: Re: [Qemu-devel] usb-storage assertions List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Andrey Korolyov Cc: Kevin Wolf , hdegoede@redhat.com, "qemu-devel@nongnu.org" On Sa, 2016-01-09 at 20:34 +0300, Andrey Korolyov wrote: > Hello, >=20 > during regular operations within linux guest with USB EHCI frontend I > am seeing process crashes with an assert during regular operations > like dpkg install: >=20 > hw/usb/dev-storage.c:334: usb_msd_handle_reset: Assertion `s->req =3D=3D > ((void *)0)' failed. >=20 > This does happen when real block backend is an USB-attached device > itself, so we are hitting some subtle race right there, because a > single change of a backend to a raw file sitting on SSD has never > triggered this block with the linux guest (but xBSD pre-reboot flush > would trigger assertion from time to time in the usb_cancel_packet() > without regarding physical backend type: >=20 > hw/usb/core.c:508: usb_cancel_packet: Assertion > `usb_packet_is_inflight(p)' failed. > ) >=20 > Since the 2.2.0 which I am running is not exactly freshest one, I > could re-check with master today or tomorrow, but log for hw/usb/ has > no related commits for intentional fixes over one or another issue. Checking would be nice, but I likewise don't expect things being different on 2.5. Most likely these are bugs in rarely taken code paths, probably because the guest cancels requests and/or resets device due to timeouts (which in turn are triggered by slow backing storage on the host). Any chance you can rebuild qemu with DEBUG_MSD enabled (in hw/usb/dev-storage.c), then trigger the asserts again, so we hopefully get a useful trail of the events triggering the bugs? Kevin, is is possible to limit transfer rates for block devices, to simplify debugging stuff like this? Preferably in a way supported by libvirt? thanks, Gerd