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

[Benjamin Gaignard]

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