Hello Hans
Thanks for your feedback. I have send a patch to the list with your suggestion.
If I dont apply my patch, but your your branch I still get the error:
Thanks!
[ 57.567944] BUG: unable to handle kernel NULL pointer dereference
at 0000000000000260
[ 57.567980] IP: [<ffffffffa07ab963>]
__vb2_perform_fileio+0x363/0x600 [videobuf2_core]
[ 57.568013] PGD 15952a067 PUD 159519067 PMD 0
[ 57.568032] Oops: 0000 [#1] SMP
[ 57.568045] Modules linked in: nfc qtec_xform gpio_xilinx
qt5023_video videobuf2_vmalloc videobuf2_dma_sg videobuf2_memops
videobuf2_core qtec_pcie qtec_cmosis qtec_white qtec_mem fglrx(PO)
spi_xilinx spi_bitbang qt5023
[ 57.568109] CPU: 1 PID: 1213 Comm: java Tainted: P O
3.11.0-qtec-standard+ #112
[ 57.568122] Hardware name: QTechnology QT5022/QT5022, BIOS
PM_2.1.0.309 X64 05/23/2013
[ 57.568134] task: ffff88014aa98000 ti: ffff88014aa94000 task.ti:
ffff88014aa94000
[ 57.568144] RIP: 0010:[<ffffffffa07ab963>] [<ffffffffa07ab963>]
__vb2_perform_fileio+0x363/0x600 [videobuf2_core]
[ 57.568168] RSP: 0018:ffff88014aa95e48 EFLAGS: 00010246
[ 57.568178] RAX: 0000000000000000 RBX: ffff88015694e870 RCX: 0000000000000000
[ 57.568187] RDX: 0000000000000000 RSI: ffff88015694c400 RDI: ffff88015694c400
[ 57.568195] RBP: ffff88014aa95e98 R08: 0000000000000000 R09: 0000000000000001
[ 57.568204] R10: ffffea00055c2880 R11: ffff88014aa95fd8 R12: ffff88015694e800
[ 57.568213] R13: 000000000021de00 R14: ffff88015727f0b8 R15: 000000000126ae20
[ 57.568224] FS: 00007fc23bbda700(0000) GS:ffff88015ed00000(0000)
knlGS:0000000000000000
[ 57.568233] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
[ 57.568241] CR2: 0000000000000260 CR3: 0000000156931000 CR4: 00000000000007e0
[ 57.568248] Stack:
[ 57.568254] ffff880159632910 0000000000000000 ffff880100000001
0000000059bd0820
[ 57.568270] ffff88014aa95f50 ffff88015727f720 ffff880159632900
ffff88015727f340
[ 57.568285] 000000000021de00 ffff88014aa95f50 ffff88014aa95ed8
ffffffffa07abe09
[ 57.568300] Call Trace:
[ 57.568328] [<ffffffffa07abe09>] vb2_fop_read+0xb9/0x110 [videobuf2_core]
[ 57.568351] [<ffffffff81534985>] v4l2_read+0x65/0xb0
[ 57.568372] [<ffffffff81166bea>] vfs_read+0x9a/0x150
[ 57.568388] [<ffffffff81167649>] SyS_read+0x49/0xa0
[ 57.568407] [<ffffffff81760479>] tracesys+0xd0/0xd5
[ 57.568415] Code: 89 c2 44 8b 4d c0 4c 8b 45 b8 0f 8f 2d 02 00 00
85 d2 48 63 c2 0f 85 86 fd ff ff 41 83 84 24 78 03 00 00 01 31 d2 4b
8b 4c c6 48 <8b> 81 60 02 00 00 85 c0 74 05 8b 41 58 89 c2 89 43 08 80
63 10
[ 57.568566] RIP [<ffffffffa07ab963>]
__vb2_perform_fileio+0x363/0x600 [videobuf2_core]
[ 57.568587] RSP <ffff88014aa95e48>
[ 57.568594] CR2: 0000000000000260
[ 57.568606] ---[ end trace d664b8a0460e8ca5 ]---
On Sun, Oct 13, 2013 at 6:42 PM, Hans Verkuil <hverkuil@xxxxxxxxx> wrote:
> Hi Ricardo,
>
> On 10/13/2013 03:03 PM, Ricardo Ribalda Delgado wrote:
>> Hello
>>
>> These days I have been testing an app that uses the old read/write
>> API. It is interfacing a videobuf2-sg driver.
>>
>> Once in a while I get an oops on the vb2_perform_fileio function.
>>
>> After digging a while I have been able to fix the bug like this:
>>
>> int vb2_fop_release(struct file *file)
>> {
>> struct video_device *vdev = video_devdata(file);
>> + struct mutex *lock = vdev->queue->lock ? vdev->queue->lock : vdev->lock;
>>
>> + if (lock)
>> + mutex_lock(lock);
>> if (file->private_data == vdev->queue->owner) {
>> vb2_queue_release(vdev->queue);
>> vdev->queue->owner = NULL;
>> }
>> + if (lock)
>> + mutex_unlock(lock);
>> return v4l2_fh_release(file);
>> }
>> EXPORT_SYMBOL_GPL(vb2_fop_release);
>>
>> (or at least, I havent seen the oops since then).
>>
>> I was wondering if this a real bug on vb2 and I shall post a proper
>> patch or the device driver is doing something out of spec.
>>
>> vb2_perform_fileio+0x372 corresponds to
>>
>> memset(&fileio->b, 0, sizeof(fileio->b));
>>
>> My theory is that:
>>
>> fileio = q->fileio;
>> if (!fileio){
>> ...
>> q->fileio = NULL;
>>
>> can be prone to race conditions if the lock is not held on release.
>
> This would not surprise me.
>
> I have a number of vb2 patches in this branch:
>
> http://git.linuxtv.org/hverkuil/media_tree.git/shortlog/refs/heads/vb2-thread
>
> Among others it replaces the 'q->fileio = NULL' hack by a proper solution.
>
> It will be interesting to see if my patch series in that branch would fix your
> problem as well.
>
> That said, I do think vb2_fop_release should take the lock regardless, although
> I would put the mutex_lock inside the 'if' that checks the owner.
>
> Regards,
>
> Hans
>
>>
>>
>> [ 308.297741] BUG: unable to handle kernel NULL pointer dereference at
>> 0000000000000260
>> [ 308.297759] IP: [<ffffffffa07a9fd2>] vb2_perform_fileio+0x372/0x610
>> [videobuf2_core]
>> [ 308.297794] PGD 159719067 PUD 158119067 PMD 0
>> [ 308.297812] Oops: 0000 #1 SMP
>> [ 308.297826] Modules linked in: qt5023_video videobuf2_dma_sg
>> qtec_xform videobuf2_vmalloc videobuf2_memops videobuf2_core
>> qtec_white qtec_mem gpio_xilinx qtec_cmosis qtec_pcie fglrx(PO)
>> spi_xilinx spi_bitbang qt5023
>> [ 308.297888] CPU: 1 PID: 2189 Comm: java Tainted: P O 3.11.0-qtec-standard #1
>> [ 308.297919] Hardware name: QTechnology QT5022/QT5022, BIOS
>> PM_2.1.0.309 X64 05/23/2013
>> [ 308.297952] task: ffff8801564e1690 ti: ffff88014dc02000 task.ti:
>> ffff88014dc02000
>> [ 308.297962] RIP: 0010:[<ffffffffa07a9fd2>] [<ffffffffa07a9fd2>]
>> vb2_perform_fileio+0x372/0x610 [videobuf2_core]
>> [ 308.297985] RSP: 0018:ffff88014dc03df8 EFLAGS: 00010202
>> [ 308.297995] RAX: 0000000000000000 RBX: ffff880158a23000 RCX: dead000000100100
>> [ 308.298003] RDX: 0000000000000000 RSI: dead000000200200 RDI: 0000000000000000
>> [ 308.298012] RBP: ffff88014dc03e58 R08: 0000000000000000 R09: 0000000000000001
>> [ 308.298020] R10: ffffea00051e8380 R11: ffff88014dc03fd8 R12: ffff880158a23070
>> [ 308.298029] R13: ffff8801549040b8 R14: 0000000000198000 R15: 0000000001887e60
>> [ 308.298040] FS: 00007f65130d5700(0000) GS:ffff88015ed00000(0000)
>> knlGS:0000000000000000
>> [ 308.298049] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> [ 308.298057] CR2: 0000000000000260 CR3: 0000000159630000 CR4: 00000000000007e0
>> [ 308.298064] Stack:
>> [ 308.298071] ffff880156416c00 0000000000198000 0000000000000000
>> ffff880100000001
>> [ 308.298087] ffff88014dc03f50 00000000810a79ca 0002000000000001
>> ffff880154904718
>> [ 308.298101] ffff880156416c00 0000000000198000 ffff880154904338
>> ffff88014dc03f50
>> [ 308.298116] Call Trace:
>> [ 308.298143] [<ffffffffa07aa3c4>] vb2_read+0x14/0x20 [videobuf2_core]
>> [ 308.298198] [<ffffffffa07aa494>] vb2_fop_read+0xc4/0x120 [videobuf2_core]
>> [ 308.298252] [<ffffffff8154ee9e>] v4l2_read+0x7e/0xc0
>> [ 308.298296] [<ffffffff8116e639>] vfs_read+0xa9/0x160
>> [ 308.298312] [<ffffffff8116e882>] SyS_read+0x52/0xb0
>> [ 308.298328] [<ffffffff81784179>] tracesys+0xd0/0xd5
>> [ 308.298335] Code: e5 d6 ff ff 83 3d be 24 00 00 04 89 c2 4c 8b 45 b0
>> 44 8b 4d b8 0f 8f 20 02 00 00 85 d2 75 32 83 83 78 03 00 00 01 4b 8b
>> 44 c5 48 <8b> 88 60 02 00 00 85 c9 0f 84 b0 00 00 00 8b 40 58 89 c2 41
>> 89
>> [ 308.298487] RIP [<ffffffffa07a9fd2>] vb2_perform_fileio+0x372/0x610
>> [videobuf2_core]
>> [ 308.298507] RSP <ffff88014dc03df8>
>> [ 308.298514] CR2: 0000000000000260
>> [ 308.298526] ---[ end trace e8f01717c96d1e41 ]---
>>
>
--
Ricardo Ribalda
--
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