Message-ID: <bf659f27-1669-86b8-df30-f1e7f9ecf371@collabora.com>
Date:   Thu, 21 Sep 2023 15:07:05 +0200
From:   Benjamin Gaignard <benjamin.gaignard@...labora.com>
To:     Hans Verkuil <hverkuil-cisco@...all.nl>, mchehab@...nel.org,
        tfiga@...omium.org, m.szyprowski@...sung.com, ming.qian@....com,
        ezequiel@...guardiasur.com.ar, p.zabel@...gutronix.de,
        gregkh@...uxfoundation.org, nicolas.dufresne@...labora.com
Cc:     linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-arm-msm@...r.kernel.org,
        linux-rockchip@...ts.infradead.org, linux-staging@...ts.linux.dev,
        kernel@...labora.com
Subject: Re: [PATCH v7 45/49] media: core: Add bitmap manage bufs array
 entries


Le 21/09/2023 à 14:46, Benjamin Gaignard a écrit :
>
> Le 21/09/2023 à 14:13, Hans Verkuil a écrit :
>> On 21/09/2023 14:05, Benjamin Gaignard wrote:
>>> Le 21/09/2023 à 12:24, Hans Verkuil a écrit :
>>>> On 21/09/2023 11:28, Benjamin Gaignard wrote:
>>>>> Le 20/09/2023 à 16:56, Hans Verkuil a écrit :
>>>>>> On 20/09/2023 16:30, Benjamin Gaignard wrote:
>>>>>> <snip>
>>>>>>
>>>>>>>>>          num_buffers = min_t(unsigned int, num_buffers,
>>>>>>>>>                      q->max_allowed_buffers - 
>>>>>>>>> vb2_get_num_buffers(q));
>>>>>>>>>      -    first_index = vb2_get_num_buffers(q);
>>>>>>>>> +    first_index = bitmap_find_next_zero_area(q->bufs_map, 
>>>>>>>>> q->max_allowed_buffers,
>>>>>>>>> +                         0, num_buffers, 0);
>>>>>>>>>            if (first_index >= q->max_allowed_buffers)
>>>>>>>>>              return 0;
>>>>>>>>> @@ -675,7 +678,13 @@ static void __vb2_queue_free(struct 
>>>>>>>>> vb2_queue *q, unsigned int buffers)
>>>>>>>>>        struct vb2_buffer *vb2_get_buffer(struct vb2_queue *q, 
>>>>>>>>> unsigned int index)
>>>>>>>>>      {
>>>>>>>>> -    if (index < q->num_buffers)
>>>>>>>>> +    if (!q->bufs_map || !q->bufs)
>>>>>>>>> +        return NULL;
>>>>>>>> I don't think this can ever happen.
>>>>>>> I got kernel crash without them.
>>>>>>> I will keep them.
>>>>>> What is the backtrace? How can this happen? It feels wrong that 
>>>>>> this can be
>>>>>> called with a vb2_queue that apparently is not properly initialized.
>>>>> I have this log when adding dump_stack() in vb2_get_buffer() if 
>>>>> !q->bufs_bitmap:
>>>>>
>>>>> [   18.924627] Call trace:
>>>>> [   18.927090]  dump_backtrace+0x94/0xec
>>>>> [   18.930787]  show_stack+0x18/0x24
>>>>> [   18.934137]  dump_stack_lvl+0x48/0x60
>>>>> [   18.937833]  dump_stack+0x18/0x24
>>>>> [   18.941166]  __vb2_queue_cancel+0x23c/0x2f0
>>>>> [   18.945365]  vb2_core_queue_release+0x24/0x6c
>>>>> [   18.949740]  vb2_queue_release+0x10/0x1c
>>>>> [   18.953677]  v4l2_m2m_ctx_release+0x20/0x40
>>>>> [   18.957892]  hantro_release+0x20/0x54
>>>>> [   18.961584]  v4l2_release+0x74/0xec
>>>>> [   18.965110]  __fput+0xb4/0x274
>>>>> [   18.968205]  __fput_sync+0x50/0x5c
>>>>> [   18.971626]  __arm64_sys_close+0x38/0x7c
>>>>> [   18.975562]  invoke_syscall+0x48/0x114
>>>>> [   18.979329]  el0_svc_common.constprop.0+0xc0/0xe0
>>>>> [   18.984068]  do_el0_svc+0x1c/0x28
>>>>> [   18.987402]  el0_svc+0x40/0xe8
>>>>> [   18.990470]  el0t_64_sync_handler+0x100/0x12c
>>>>> [   18.994842]  el0t_64_sync+0x190/0x194
>>>>>
>>>>> This happen at boot time when hantro driver is open and close 
>>>>> without other actions.
>>>> Ah, now I see the problem. q->bufs and q->bufs_map are allocated in
>>>> vb2_core_create_bufs and vb2_core_reqbufs, but they should be 
>>>> allocated
>>>> in vb2_queue_init: that's the counterpart of vb2_core_queue_release.

Hans,
I think we are doing loops in your comment :-)
https://patchwork.kernel.org/comment/25496456/

Regards,
Benjamin

>>>>
>>>> With that change you shouldn't have to check for q->bufs/bufs_map 
>>>> anymore.
>>> It is a better solution but even like this vb2_core_queue_release() 
>>> is called
>>> at least 2 times on the same vivid queue and without testing 
>>> q->bufs_bitmap
>>> makes kernel crash.
>> Do you have a stacktrace for that? Perhaps vb2_core_queue_release 
>> should check
>> for q->bufs/q->bufs_map and return if those are NULL. But it could 
>> also be a
>> bug that it is called twice, it just was never noticed because it was 
>> harmless
>> before.
>
> I have added some printk to log that when running test-media on vivid:
>
> [  130.497426] vb2_core_queue_init queue cap-0000000050d195ab allocate 
> q->bufs 00000000dc2c15ed and q->bufs_bitmap 000000008173fc5a
> ...
> [  130.733967] vb2_core_queue_release queue cap-0000000050d195ab 
> release q->bufs and q->bufs_bitmap
> [  133.866345] vb2_get_buffer queue cap-0000000050d195ab 
> q->bufs_bitmap is NULL
> [  133.873454] CPU: 1 PID: 321 Comm: v4l2-ctl Not tainted 6.6.0-rc1+ #542
> [  133.879997] Hardware name: NXP i.MX8MQ EVK (DT)
> [  133.884536] Call trace:
> [  133.886988]  dump_backtrace+0x94/0xec
> [  133.890673]  show_stack+0x18/0x24
> [  133.894002]  dump_stack_lvl+0x48/0x60
> [  133.897681]  dump_stack+0x18/0x24
> [  133.901009]  __vb2_queue_cancel+0x250/0x31c
> [  133.905209]  vb2_core_queue_release+0x24/0x88
> [  133.909580]  _vb2_fop_release+0xb0/0xbc
> [  133.913428]  vb2_fop_release+0x2c/0x58
> [  133.917187]  vivid_fop_release+0x80/0x388 [vivid]
> [  133.921948]  v4l2_release+0x74/0xec
> [  133.925452]  __fput+0xb4/0x274
> [  133.928520]  __fput_sync+0x50/0x5c
> [  133.931934]  __arm64_sys_close+0x38/0x7c
> [  133.935868]  invoke_syscall+0x48/0x114
> [  133.939630]  el0_svc_common.constprop.0+0x40/0xe0
> [  133.944349]  do_el0_svc+0x1c/0x28
> [  133.947677]  el0_svc+0x40/0xe8
> [  133.950741]  el0t_64_sync_handler+0x100/0x12c
> [  133.955109]  el0t_64_sync+0x190/0x194
>
> and later I have a call to reqbufs on the same queue without call to 
> vb2_core_queue_init before
>
> [   58.696812] __vb2_queue_alloc queue cap- 
> 0000000050d195abq->bufs_bitmap is NULL
> [   58.704148] CPU: 1 PID: 319 Comm: v4l2-compliance Not tainted 
> 6.6.0-rc1+ #544
> [   58.711291] Hardware name: NXP i.MX8MQ EVK (DT)
> [   58.715826] Call trace:
> [   58.718274]  dump_backtrace+0x94/0xec
> [   58.721951]  show_stack+0x18/0x24
> [   58.725274]  dump_stack_lvl+0x48/0x60
> [   58.728946]  dump_stack+0x18/0x24
> [   58.732268]  __vb2_queue_alloc+0x4a8/0x50c
> [   58.736374]  vb2_core_reqbufs+0x274/0x46c
> [   58.740391]  vb2_ioctl_reqbufs+0xb0/0xe8
> [   58.744320]  vidioc_reqbufs+0x50/0x64 [vivid]
> [   58.748717]  v4l_reqbufs+0x50/0x64
> [   58.752125]  __video_do_ioctl+0x164/0x3c8
> [   58.756140]  video_usercopy+0x200/0x668
> [   58.759982]  video_ioctl2+0x18/0x28
> [   58.763475]  v4l2_ioctl+0x40/0x60
> [   58.766798]  __arm64_sys_ioctl+0xac/0xf0
> [   58.770730]  invoke_syscall+0x48/0x114
> [   58.774487]  el0_svc_common.constprop.0+0x40/0xe0
> [   58.779199]  do_el0_svc+0x1c/0x28
> [   58.782520]  el0_svc+0x40/0xe8
> [   58.785580]  el0t_64_sync_handler+0x100/0x12c
> [   58.789942]  el0t_64_sync+0x190/0x194
>
>>
>> Regards,
>>
>>     Hans
>>
>>>> Regards,
>>>>
>>>>      Hans
>>>>
>>>>>>>>> +
>>>>>>>>> +    return (bitmap_weight(q->bufs_map, 
>>>>>>>>> q->max_allowed_buffers) > 0);
>>>>>>>> How about:
>>>>>>>>
>>>>>>>>        return vb2_get_num_buffers(q) > 0;
>>>>>>> vb2_get_num_buffers is defined in videobuf2-core.c, I'm not sure 
>>>>>>> that
>>>>>>> an inline function could depend of a module function.
>>>>>> Not a problem. E.g. v4l2-ctrls.h is full of such static inlines.
>>>>>>
>>>>>> Regards,
>>>>>>
>>>>>>       Hans
>>>>>>
>>

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