From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753383AbdJMXOB (ORCPT ); Fri, 13 Oct 2017 19:14:01 -0400 Received: from osg.samsung.com ([64.30.133.232]:35434 "EHLO osg.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751571AbdJMXNq (ORCPT ); Fri, 13 Oct 2017 19:13:46 -0400 X-Amavis-Alert: BAD HEADER SECTION, Duplicate header field: "References" From: Shuah Khan To: mchehab@kernel.org, hansverk@cisco.com, kgene@kernel.org, krzk@kernel.org, s.nawrocki@samsung.com, shailendra.v@samsung.com, shuah@kernel.org, Julia.Lawall@lip6.fr, kyungmin.park@samsung.com, kamil@wypas.org, jtp.park@samsung.com, a.hajda@samsung.com Cc: Shuah Khan , linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: [PATCH 2/2] media: s5p-mfc: fix lockdep warning Date: Fri, 13 Oct 2017 17:13:37 -0600 Message-Id: <4887afc17a24fbd103e8616b463269cef8482bf3.1507935819.git.shuahkh@osg.samsung.com> X-Mailer: git-send-email 2.11.0 In-Reply-To: References: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The driver mmap functions shouldn't take lock when calling vb2_mmap(). Fix it to not take the lock. The following lockdep warning is fixed with this change. [ 2106.181412] ====================================================== [ 2106.187563] WARNING: possible circular locking dependency detected [ 2106.193718] 4.14.0-rc2-00002-gfab205f-dirty #4 Not tainted [ 2106.199175] ------------------------------------------------------ [ 2106.205328] qtdemux0:sink/2614 is trying to acquire lock: [ 2106.210701] (&dev->mfc_mutex){+.+.}, at: [] s5p_mfc_mmap+0x28/0xd4 [s5p_mfc] [ 2106.218672] [ 2106.218672] but task is already holding lock: [ 2106.224477] (&mm->mmap_sem){++++}, at: [] vm_mmap_pgoff+0x44/0xb8 [ 2106.231497] [ 2106.231497] which lock already depends on the new lock. [ 2106.231497] [ 2106.239642] [ 2106.239642] the existing dependency chain (in reverse order) is: [ 2106.247095] [ 2106.247095] -> #1 (&mm->mmap_sem){++++}: [ 2106.252473] __might_fault+0x80/0xb0 [ 2106.256567] video_usercopy+0x1cc/0x510 [videodev] [ 2106.261845] v4l2_ioctl+0xa4/0xdc [videodev] [ 2106.266596] do_vfs_ioctl+0xa0/0xa18 [ 2106.270667] SyS_ioctl+0x34/0x5c [ 2106.274395] ret_fast_syscall+0x0/0x28 [ 2106.278637] [ 2106.278637] -> #0 (&dev->mfc_mutex){+.+.}: [ 2106.284186] lock_acquire+0x6c/0x88 [ 2106.288173] __mutex_lock+0x68/0xa34 [ 2106.292244] mutex_lock_interruptible_nested+0x1c/0x24 [ 2106.297893] s5p_mfc_mmap+0x28/0xd4 [s5p_mfc] [ 2106.302747] v4l2_mmap+0x54/0x88 [videodev] [ 2106.307409] mmap_region+0x3a8/0x638 [ 2106.311480] do_mmap+0x330/0x3a4 [ 2106.315207] vm_mmap_pgoff+0x90/0xb8 [ 2106.319279] SyS_mmap_pgoff+0x90/0xc0 [ 2106.323439] ret_fast_syscall+0x0/0x28 [ 2106.327683] [ 2106.327683] other info that might help us debug this: [ 2106.327683] [ 2106.335656] Possible unsafe locking scenario: [ 2106.335656] [ 2106.341548] CPU0 CPU1 [ 2106.346053] ---- ---- [ 2106.350559] lock(&mm->mmap_sem); [ 2106.353939] lock(&dev->mfc_mutex); [ 2106.353939] lock(&dev->mfc_mutex); [ 2106.365897] lock(&dev->mfc_mutex); [ 2106.369450] [ 2106.369450] *** DEADLOCK *** [ 2106.369450] [ 2106.375344] 1 lock held by qtdemux0:sink/2614: [ 2106.379762] #0: (&mm->mmap_sem){++++}, at: [] vm_mmap_pgoff+0x44/0xb8 [ 2106.387214] [ 2106.387214] stack backtrace: [ 2106.391550] CPU: 7 PID: 2614 Comm: qtdemux0:sink Not tainted 4.14.0-rc2-00002-gfab205f-dirty #4 [ 2106.400213] Hardware name: SAMSUNG EXYNOS (Flattened Device Tree) [ 2106.406285] [] (unwind_backtrace) from [] (show_stack+0x10/0x14) [ 2106.413995] [] (show_stack) from [] (dump_stack+0x98/0xc4) [ 2106.421187] [] (dump_stack) from [] (print_circular_bug+0x254/0x410) [ 2106.429245] [] (print_circular_bug) from [] (check_prev_add+0x468/0x938) [ 2106.437651] [] (check_prev_add) from [] (__lock_acquire+0x1314/0x14fc) [ 2106.445883] [] (__lock_acquire) from [] (lock_acquire+0x6c/0x88) [ 2106.453596] [] (lock_acquire) from [] (__mutex_lock+0x68/0xa34) [ 2106.461221] [] (__mutex_lock) from [] (mutex_lock_interruptible_nested+0x1c/0x24) [ 2106.470425] [] (mutex_lock_interruptible_nested) from [] (s5p_mfc_mmap+0x28/0xd4 [s5p_mfc]) [ 2106.480494] [] (s5p_mfc_mmap [s5p_mfc]) from [] (v4l2_mmap+0x54/0x88 [videodev]) [ 2106.489575] [] (v4l2_mmap [videodev]) from [] (mmap_region+0x3a8/0x638) [ 2106.497875] [] (mmap_region) from [] (do_mmap+0x330/0x3a4) [ 2106.505068] [] (do_mmap) from [] (vm_mmap_pgoff+0x90/0xb8) [ 2106.512260] [] (vm_mmap_pgoff) from [] (SyS_mmap_pgoff+0x90/0xc0) [ 2106.520059] [] (SyS_mmap_pgoff) from [] (ret_fast_syscall+0x0/0x28) Signed-off-by: Shuah Khan Suggested-by: Hans Verkuil --- drivers/media/platform/s5p-mfc/s5p_mfc.c | 3 --- 1 file changed, 3 deletions(-) diff --git a/drivers/media/platform/s5p-mfc/s5p_mfc.c b/drivers/media/platform/s5p-mfc/s5p_mfc.c index 4c253fb..40c18b4 100644 --- a/drivers/media/platform/s5p-mfc/s5p_mfc.c +++ b/drivers/media/platform/s5p-mfc/s5p_mfc.c @@ -1047,8 +1047,6 @@ static int s5p_mfc_mmap(struct file *file, struct vm_area_struct *vma) unsigned long offset = vma->vm_pgoff << PAGE_SHIFT; int ret; - if (mutex_lock_interruptible(&dev->mfc_mutex)) - return -ERESTARTSYS; if (offset < DST_QUEUE_OFF_BASE) { mfc_debug(2, "mmaping source\n"); ret = vb2_mmap(&ctx->vq_src, vma); @@ -1057,7 +1055,6 @@ static int s5p_mfc_mmap(struct file *file, struct vm_area_struct *vma) vma->vm_pgoff -= (DST_QUEUE_OFF_BASE >> PAGE_SHIFT); ret = vb2_mmap(&ctx->vq_dst, vma); } - mutex_unlock(&dev->mfc_mutex); return ret; } -- 2.7.4