Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755608Ab3EQJw3 (ORCPT ); Fri, 17 May 2013 05:52:29 -0400 Received: from smtp-vbr2.xs4all.nl ([194.109.24.22]:1094 "EHLO smtp-vbr2.xs4all.nl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754062Ab3EQJw2 (ORCPT ); Fri, 17 May 2013 05:52:28 -0400 From: Hans Verkuil To: Sander Eikelenboom Subject: Re: [media] cx25821 regression from 3.9: BUG: bad unlock balance detected! Date: Fri, 17 May 2013 11:52:17 +0200 User-Agent: KMail/1.13.7 (Linux/3.9.0-rc5-tschai; KDE/4.8.4; x86_64; ; ) Cc: linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, Mauro Carvalho Chehab References: <1139404719.20130516194142@eikelenboom.it> <201305171025.24166.hverkuil@xs4all.nl> <1756541549.20130517110450@eikelenboom.it> In-Reply-To: <1756541549.20130517110450@eikelenboom.it> MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <201305171152.17746.hverkuil@xs4all.nl> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5259 Lines: 123 On Fri May 17 2013 11:04:50 Sander Eikelenboom wrote: > > Friday, May 17, 2013, 10:25:24 AM, you wrote: > > > On Thu May 16 2013 19:41:42 Sander Eikelenboom wrote: > >> Hi Hans / Mauro, > >> > >> With 3.10.0-rc1 (including the cx25821 changes from Hans), I get the bug below which wasn't present with 3.9. > > > How do I reproduce this? I've tried to, but I can't make this happen. > > > Looking at the code I can't see how it could hit this bug anyway. > > I'm using "motion" to grab and process 6 from the video streams of the card i have (card with 8 inputs). > It seems the cx25821 underwent quite some changes between 3.9 and 3.10. It did. > And in the past there have been some more locking issues around mmap and media devices, although they seem to appear as circular locking dependencies and with different devices. > - http://www.mail-archive.com/linux-media@vger.kernel.org/msg46217.html > - Under kvm: http://www.spinics.net/lists/linux-media/msg63322.html Neither of those are related to this issue. > > - Perhaps that running in a VM could have to do with it ? > - The driver on 3.9 occasionaly gives this, probably latency related (but continues to work): > cx25821: cx25821_video_wakeup: 2 buffers handled (should be 1) > > Could it be something double unlocking in that path ? > > - Is there any extra debugging i could enable that could pinpoint the issue ? Try this patch: diff --git a/drivers/media/pci/cx25821/cx25821-core.c b/drivers/media/pci/cx25821/cx25821-core.c index b762c5b..8f8d0e0 100644 --- a/drivers/media/pci/cx25821/cx25821-core.c +++ b/drivers/media/pci/cx25821/cx25821-core.c @@ -1208,7 +1208,6 @@ void cx25821_free_buffer(struct videobuf_queue *q, struct cx25821_buffer *buf) struct videobuf_dmabuf *dma = videobuf_to_dma(&buf->vb); BUG_ON(in_interrupt()); - videobuf_waiton(q, &buf->vb, 0, 0); videobuf_dma_unmap(q->dev, dma); videobuf_dma_free(dma); btcx_riscmem_free(to_pci_dev(q->dev), &buf->risc); I don't think the waiton is really needed for this driver. What really should happen is that videobuf is replaced by videobuf2 in this driver, but that's a fair amount of work. Regards, Hans > > > -- > > Sander > > > > > Regards, > > > Hans > > >> > >> -- > >> Sander > >> > >> > >> [ 53.004968] ===================================== > >> [ 53.004968] [ BUG: bad unlock balance detected! ] > >> [ 53.004968] 3.10.0-rc1-20130516-jens+ #1 Not tainted > >> [ 53.004968] ------------------------------------- > >> [ 53.004968] motion/3328 is trying to release lock (&dev->lock) at: > >> [ 53.004968] [] mutex_unlock+0x9/0x10 > >> [ 53.004968] but there are no more locks to release! > >> [ 53.004968] > >> [ 53.004968] other info that might help us debug this: > >> [ 53.004968] 1 lock held by motion/3328: > >> [ 53.004968] #0: (&mm->mmap_sem){++++++}, at: [] vm_munmap+0x3e/0x70 > >> [ 53.004968] > >> [ 53.004968] stack backtrace: > >> [ 53.004968] CPU: 1 PID: 3328 Comm: motion Not tainted 3.10.0-rc1-20130516-jens+ #1 > >> [ 53.004968] Hardware name: Xen HVM domU, BIOS 4.3-unstable 05/16/2013 > >> [ 53.004968] ffffffff819be5f9 ffff88002ac35c58 ffffffff819b9029 ffff88002ac35c88 > >> [ 53.004968] ffffffff810e615e ffff88002ac35cb8 ffff88002b7c18a8 ffffffff819be5f9 > >> [ 53.004968] 00000000ffffffff ffff88002ac35d28 ffffffff810eb17e ffffffff810e7ba5 > >> [ 53.004968] Call Trace: > >> [ 53.004968] [] ? mutex_unlock+0x9/0x10 > >> [ 53.004968] [] dump_stack+0x19/0x1b > >> [ 53.004968] [] print_unlock_imbalance_bug+0xfe/0x110 > >> [ 53.004968] [] ? mutex_unlock+0x9/0x10 > >> [ 53.004968] [] lock_release_non_nested+0x1ce/0x320 > >> [ 53.004968] [] ? debug_check_no_locks_freed+0x105/0x1b0 > >> [ 53.353529] [] ? mutex_unlock+0x9/0x10 > >> [ 53.353529] [] lock_release+0xfc/0x250 > >> [ 53.353529] [] __mutex_unlock_slowpath+0xb2/0x1f0 > >> [ 53.353529] [] mutex_unlock+0x9/0x10 > >> [ 53.353529] [] videobuf_waiton+0x55/0x230 > >> [ 53.353529] [] ? tlb_finish_mmu+0x32/0x50 > >> [ 53.353529] [] ? unmap_region+0xc6/0x100 > >> [ 53.353529] [] ? kmem_cache_free+0x195/0x230 > >> [ 53.353529] [] cx25821_free_buffer+0x49/0xa0 > >> [ 53.353529] [] cx25821_buffer_release+0x9/0x10 > >> [ 53.353529] [] videobuf_vm_close+0xc5/0x160 > >> [ 53.353529] [] remove_vma+0x25/0x60 > >> [ 53.353529] [] do_munmap+0x307/0x410 > >> [ 53.353529] [] vm_munmap+0x4c/0x70 > >> [ 53.353529] [] SyS_munmap+0x9/0x10 > >> [ 53.353529] [] system_call_fastpath+0x16/0x1b > >> > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/