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Message-ID: <c8b7db47-3875-a10b-8d81-a0b3dcbc564a@collabora.com>
Date: Thu, 21 Sep 2023 14:46:40 +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 14:13, 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.
>>>
>>> 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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