From: Hans Verkuil <hverkuil@xs4all.nl>
To: Eugen.Hristev@microchip.com, linux-media@vger.kernel.org,
jacopo@jmondi.org
Cc: devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
Claudiu.Beznea@microchip.com, robh+dt@kernel.org,
Nicolas.Ferre@microchip.com
Subject: Re: [PATCH v9 06/13] media: atmel: atmel-isc-base: use mutex to lock awb workqueue from streaming
Date: Fri, 29 Apr 2022 10:18:23 +0200 [thread overview]
Message-ID: <20fd8dc0-bcb4-d18b-a143-5e658391474d@xs4all.nl> (raw)
In-Reply-To: <2510d479-5eef-6ef6-5d32-41f70217eb52@microchip.com>
On 29/04/2022 10:08, Eugen.Hristev@microchip.com wrote:
> On 4/29/22 10:41 AM, Hans Verkuil wrote:
>> Hi Eugen,
>>
>> On 10/03/2022 10:51, Eugen Hristev wrote:
>>> The AWB workqueue runs in a kernel thread and needs to be synchronized
>>> w.r.t. the streaming status.
>>> It is possible that streaming is stopped while the AWB workq is running.
>>> In this case it is likely that the check for vb2_start_streaming_called is done
>>> at one point in time, but the AWB computations are done later, including a call
>>> to isc_update_profile, which requires streaming to be started.
>>> Thus , isc_update_profile will fail if during this operation sequence the
>>> streaming was stopped.
>>> To solve this issue, a mutex is added, that will serialize the awb work and
>>> streaming stopping, with the mention that either streaming is stopped
>>> completely including termination of the last frame is done, and after that
>>> the AWB work can check stream status and stop; either first AWB work is
>>> completed and after that the streaming can stop correctly.
>>> The awb spin lock cannot be used since this spinlock is taken in the same
>>> context and using it in the stop streaming will result in a recursion BUG.
>>
>> Please keep the line length in a commit log to no more than 75.
>>
>>>
>>> Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
>>> Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
>>> ---
>>> drivers/media/platform/atmel/atmel-isc-base.c | 29 ++++++++++++++++---
>>> drivers/media/platform/atmel/atmel-isc.h | 2 ++
>>> 2 files changed, 27 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/drivers/media/platform/atmel/atmel-isc-base.c b/drivers/media/platform/atmel/atmel-isc-base.c
>>
>> <snip>
>>
>>> @@ -1548,6 +1564,7 @@ static int isc_s_awb_ctrl(struct v4l2_ctrl *ctrl)
>>> */
>>> v4l2_ctrl_activate(isc->do_wb_ctrl, false);
>>> }
>>> + mutex_unlock(&isc->awb_mutex);
>>
>> Huh? What is this unlock doing here? Am I missing something?
>
> Hello Hans,
>
> Sorry. It looks like the corresponding mutex_lock was lost when I
> rebased the series over the patch to use 'is_streaming' instead of
> 'stop' variable.
> In version 3, the mutex_lock was there :
>
> https://www.spinics.net/lists/linux-media/msg204059.html
>
> Somehow a race problem did not occur in this specific critical area in
> my tests.
>
> I will resend this patch as a v10 , or the whole series if you have
> other comments on the other patches? How would you prefer ?
I have more comments (just finished the full review), so a v10 is definitely
needed.
Regards,
Hans
>
> Thanks,
> Eugen
>
>>
>> Regards,
>>
>> Hans
>>
>>>
>>> /* if we have autowhitebalance on, start histogram procedure */
>>> if (ctrls->awb == ISC_WB_AUTO &&
>>> @@ -1740,6 +1757,7 @@ static void isc_async_unbind(struct v4l2_async_notifier *notifier,
>>> {
>>> struct isc_device *isc = container_of(notifier->v4l2_dev,
>>> struct isc_device, v4l2_dev);
>>> + mutex_destroy(&isc->awb_mutex);
>>> cancel_work_sync(&isc->awb_work);
>>> video_unregister_device(&isc->video_dev);
>>> v4l2_ctrl_handler_free(&isc->ctrls.handler);
>>> @@ -1850,6 +1868,8 @@ static int isc_async_complete(struct v4l2_async_notifier *notifier)
>>> isc->current_subdev = container_of(notifier,
>>> struct isc_subdev_entity, notifier);
>>> mutex_init(&isc->lock);
>>> + mutex_init(&isc->awb_mutex);
>>> +
>>> init_completion(&isc->comp);
>>>
>>> /* Initialize videobuf2 queue */
>>> @@ -1930,6 +1950,7 @@ static int isc_async_complete(struct v4l2_async_notifier *notifier)
>>> video_unregister_device(vdev);
>>>
>>> isc_async_complete_err:
>>> + mutex_destroy(&isc->awb_mutex);
>>> mutex_destroy(&isc->lock);
>>> return ret;
>>> }
>>> diff --git a/drivers/media/platform/atmel/atmel-isc.h b/drivers/media/platform/atmel/atmel-isc.h
>>> index 9cc69c3ae26d..f98f25a55e73 100644
>>> --- a/drivers/media/platform/atmel/atmel-isc.h
>>> +++ b/drivers/media/platform/atmel/atmel-isc.h
>>> @@ -229,6 +229,7 @@ enum isc_scaler_pads {
>>> *
>>> * @lock: lock for serializing userspace file operations
>>> * with ISC operations
>>> + * @awb_mutex: serialize access to streaming status from awb work queue
>>> * @awb_lock: lock for serializing awb work queue operations
>>> * with DMA/buffer operations
>>> *
>>> @@ -307,6 +308,7 @@ struct isc_device {
>>> struct work_struct awb_work;
>>>
>>> struct mutex lock;
>>> + struct mutex awb_mutex;
>>> spinlock_t awb_lock;
>>>
>>> struct regmap_field *pipeline[ISC_PIPE_LINE_NODE_NUM];
>>
>
next prev parent reply other threads:[~2022-04-29 8:18 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-10 9:51 [PATCH v9 00/13] media: atmel: atmel-isc: implement media controller Eugen Hristev
2022-03-10 9:51 ` [PATCH v9 01/13] media: atmel: atmel-isc-base: use streaming status when queueing buffers Eugen Hristev
2022-03-10 9:51 ` [PATCH v9 02/13] media: atmel: atmel-isc-base: replace is_streaming call in s_fmt_vid_cap Eugen Hristev
2022-03-10 9:51 ` [PATCH v9 03/13] media: atmel: atmel-isc: remove redundant comments Eugen Hristev
2022-03-10 9:51 ` [PATCH v9 04/13] media: atmel: atmel-isc: implement media controller Eugen Hristev
2022-03-10 9:51 ` [PATCH v9 05/13] media: atmel: atmel-sama5d2-isc: fix wrong mask in YUYV format check Eugen Hristev
2022-03-10 9:51 ` [PATCH v9 06/13] media: atmel: atmel-isc-base: use mutex to lock awb workqueue from streaming Eugen Hristev
2022-04-29 7:41 ` Hans Verkuil
2022-04-29 8:08 ` Eugen.Hristev
2022-04-29 8:18 ` Hans Verkuil [this message]
2022-03-10 9:51 ` [PATCH v9 07/13] media: atmel: atmel-isc: compact the controller formats list Eugen Hristev
2022-03-10 9:51 ` [PATCH v9 08/13] media: atmel: atmel-isc: change format propagation to subdev into only verification Eugen Hristev
2022-04-29 8:17 ` Hans Verkuil
2022-04-29 8:28 ` Eugen.Hristev
2022-04-29 8:43 ` Hans Verkuil
2022-04-29 9:58 ` Jacopo Mondi
2022-04-29 10:03 ` Hans Verkuil
2022-04-29 10:09 ` Eugen.Hristev
2022-04-29 10:07 ` Laurent Pinchart
2022-04-29 10:13 ` Hans Verkuil
2022-04-29 10:20 ` Laurent Pinchart
2022-04-29 11:17 ` Hans Verkuil
2022-04-29 12:02 ` Laurent Pinchart
2022-04-29 12:23 ` Hans Verkuil
2022-04-29 12:28 ` Laurent Pinchart
2022-04-29 12:38 ` Jacopo Mondi
2022-04-29 12:47 ` Laurent Pinchart
2022-04-29 12:50 ` Hans Verkuil
2022-04-29 12:59 ` Eugen.Hristev
2022-03-10 9:51 ` [PATCH v9 09/13] media: atmel: atmel-sama7g5-isc: remove stray line Eugen Hristev
2022-03-10 9:51 ` [PATCH v9 10/13] dt-bindings: media: microchip,xisc: add bus-width of 14 Eugen Hristev
2022-03-10 9:52 ` [PATCH v9 11/13] ARM: dts: at91: sama7g5: add nodes for video capture Eugen Hristev
2022-03-10 9:52 ` [PATCH v9 12/13] ARM: configs: at91: sama7: add xisc and csi2dc Eugen Hristev
2022-03-10 9:52 ` [PATCH v9 13/13] ARM: multi_v7_defconfig: add atmel video pipeline modules Eugen Hristev
2022-04-29 8:05 ` [PATCH v9 00/13] media: atmel: atmel-isc: implement media controller Hans Verkuil
2022-04-29 8:20 ` Eugen.Hristev
2022-04-29 8:33 ` Hans Verkuil
2022-04-29 8:39 ` Eugen.Hristev
2022-04-29 8:45 ` Hans Verkuil
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