Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965899AbcJYNTI (ORCPT ); Tue, 25 Oct 2016 09:19:08 -0400 Received: from mx1.redhat.com ([209.132.183.28]:43264 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935081AbcJYNTG (ORCPT ); Tue, 25 Oct 2016 09:19:06 -0400 Date: Tue, 25 Oct 2016 16:19:03 +0300 From: "Michael S. Tsirkin" To: Amit Shah Cc: Matt Redfearn , stable@vger.kernel.org, Greg Kroah-Hartman , Arnd Bergmann , linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org Subject: Re: [PATCH] virtio: console: Unlock vqs while freeing buffers Message-ID: <20161025161247-mutt-send-email-mst@kernel.org> References: <1476183915-13625-1-git-send-email-matt.redfearn@imgtec.com> <20161025071803.GG2138@amit-lp.rh> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20161025071803.GG2138@amit-lp.rh> X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.32]); Tue, 25 Oct 2016 13:19:05 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1799 Lines: 45 On Tue, Oct 25, 2016 at 12:48:03PM +0530, Amit Shah wrote: > On (Tue) 11 Oct 2016 [12:05:15], Matt Redfearn wrote: > > Commit c6017e793b93 ("virtio: console: add locks around buffer removal > > in port unplug path") added locking around the freeing of buffers in the > > vq. However, when free_buf() is called with can_sleep = true and rproc > > is enabled, it calls dma_free_coherent() directly, requiring interrupts > > to be enabled. Currently a WARNING is triggered due to the spin locking > > around free_buf, with a call stack like this: > > > > WARNING: CPU: 3 PID: 121 at ./include/linux/dma-mapping.h:433 > > free_buf+0x1a8/0x288 > > Call Trace: > > [<8040c538>] show_stack+0x74/0xc0 > > [<80757240>] dump_stack+0xd0/0x110 > > [<80430d98>] __warn+0xfc/0x130 > > [<80430ee0>] warn_slowpath_null+0x2c/0x3c > > [<807e7c6c>] free_buf+0x1a8/0x288 > > [<807ea590>] remove_port_data+0x50/0xac > > [<807ea6a0>] unplug_port+0xb4/0x1bc > > [<807ea858>] virtcons_remove+0xb0/0xfc > > [<807b6734>] virtio_dev_remove+0x58/0xc0 > > [<807f918c>] __device_release_driver+0xac/0x134 > > [<807f924c>] device_release_driver+0x38/0x50 > > [<807f7edc>] bus_remove_device+0xfc/0x130 > > [<807f4b74>] device_del+0x17c/0x21c > > [<807f4c38>] device_unregister+0x24/0x38 > > [<807b6b50>] unregister_virtio_device+0x28/0x44 > > > > Fix this by restructuring the loops to allow the locks to only be taken > > where it is necessary to protect the vqs, and release it while the > > buffer is being freed. > > > > Fixes: c6017e793b93 ("virtio: console: add locks around buffer removal in port unplug path") > > Cc: stable@vger.kernel.org > > Signed-off-by: Matt Redfearn > > Reviewed-by: Amit Shah > > Michael, can you pick this up? > > Thanks, > > Amit Sure.