Re: [PATCH v7 45/49] media: core: Add bitmap manage bufs array entries

Benjamin Gaignard
2023-09-21T09:28:13Z

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.

>
>>>> +
>>>> +    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
>