Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752819AbcJKLWy (ORCPT ); Tue, 11 Oct 2016 07:22:54 -0400 Received: from mailapp02.imgtec.com ([217.156.133.132]:63078 "EHLO mailapp01.imgtec.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752015AbcJKLWw (ORCPT ); Tue, 11 Oct 2016 07:22:52 -0400 From: Matt Redfearn To: Amit Shah CC: Matt Redfearn , , "Greg Kroah-Hartman" , Arnd Bergmann , , Subject: [PATCH] virtio: console: Unlock vqs while freeing buffers Date: Tue, 11 Oct 2016 12:05:15 +0100 Message-ID: <1476183915-13625-1-git-send-email-matt.redfearn@imgtec.com> X-Mailer: git-send-email 2.7.4 MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.150.130.83] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2837 Lines: 80 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 --- drivers/char/virtio_console.c | 22 ++++++++++++++++------ 1 file changed, 16 insertions(+), 6 deletions(-) diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c index 5da47e26a012..4aae0d27e382 100644 --- a/drivers/char/virtio_console.c +++ b/drivers/char/virtio_console.c @@ -1540,19 +1540,29 @@ static void remove_port_data(struct port *port) spin_lock_irq(&port->inbuf_lock); /* Remove unused data this port might have received. */ discard_port_data(port); + spin_unlock_irq(&port->inbuf_lock); /* Remove buffers we queued up for the Host to send us data in. */ - while ((buf = virtqueue_detach_unused_buf(port->in_vq))) - free_buf(buf, true); - spin_unlock_irq(&port->inbuf_lock); + do { + spin_lock_irq(&port->inbuf_lock); + buf = virtqueue_detach_unused_buf(port->in_vq); + spin_unlock_irq(&port->inbuf_lock); + if (buf) + free_buf(buf, true); + } while (buf); spin_lock_irq(&port->outvq_lock); reclaim_consumed_buffers(port); + spin_unlock_irq(&port->outvq_lock); /* Free pending buffers from the out-queue. */ - while ((buf = virtqueue_detach_unused_buf(port->out_vq))) - free_buf(buf, true); - spin_unlock_irq(&port->outvq_lock); + do { + spin_lock_irq(&port->outvq_lock); + buf = virtqueue_detach_unused_buf(port->out_vq); + spin_unlock_irq(&port->outvq_lock); + if (buf) + free_buf(buf, true); + } while (buf); } /* -- 2.7.4