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media: v4l2-mem2mem: Avoid calling .device_run in v4l2_m2m_job_finish

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v4l2_m2m_job_finish() is typically called when
DMA operations complete, in interrupt handlers or DMA
completion callbacks. Calling .device_run from v4l2_m2m_job_finish
creates a nasty re-entrancy path into the driver.

Moreover, some implementation of .device_run might need to sleep,
as is the case for drivers supporting the Request API,
where controls are applied via v4l2_ctrl_request_setup,
which takes the ctrl handler mutex.

This commit adds a deferred context that calls v4l2_m2m_try_run,
and gets scheduled by v4l2_m2m_job_finish().

Before this change, device_run would be called from these
paths:

vb2_m2m_request_queue, or
v4l2_m2m_streamon, or
v4l2_m2m_qbuf
  v4l2_m2m_try_schedule
    v4l2_m2m_try_run
      .device_run

v4l2_m2m_job_finish
  v4l2_m2m_try_run
    .device_run

After this change, the latter is now gone and instead:

v4l2_m2m_device_run_work
  v4l2_m2m_try_run
    .device_run

Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
This commit is contained in:
Ezequiel Garcia 2018-10-18 14:02:23 -04:00 committed by Mauro Carvalho Chehab
parent cbec2836f8
commit cbd9463da1
1 changed files with 24 additions and 1 deletions
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25
drivers/media/v4l2-core/v4l2-mem2mem.c
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@ -87,6 +87,7 @@ static const char * const m2m_entity_name[] = {
* @curr_ctx: currently running instance
* @job_queue: instances queued to run
* @job_spinlock: protects job_queue
* @job_work: worker to run queued jobs.
* @m2m_ops: driver callbacks
*/
struct v4l2_m2m_dev {
@ -103,6 +104,7 @@ struct v4l2_m2m_dev {
struct list_head job_queue;
spinlock_t job_spinlock;
struct work_struct job_work;
const struct v4l2_m2m_ops *m2m_ops;
};
@ -244,6 +246,9 @@ EXPORT_SYMBOL(v4l2_m2m_get_curr_priv);
* @m2m_dev: per-device context
*
* Get next transaction (if present) from the waiting jobs list and run it.
*
* Note that this function can run on a given v4l2_m2m_ctx context,
* but call .device_run for another context.
*/
static void v4l2_m2m_try_run(struct v4l2_m2m_dev *m2m_dev)
{
@ -362,6 +367,18 @@ void v4l2_m2m_try_schedule(struct v4l2_m2m_ctx *m2m_ctx)
}
EXPORT_SYMBOL_GPL(v4l2_m2m_try_schedule);
/**
* v4l2_m2m_device_run_work() - run pending jobs for the context
* @work: Work structure used for scheduling the execution of this function.
*/
static void v4l2_m2m_device_run_work(struct work_struct *work)
{
struct v4l2_m2m_dev *m2m_dev =
container_of(work, struct v4l2_m2m_dev, job_work);
v4l2_m2m_try_run(m2m_dev);
}
/**
* v4l2_m2m_cancel_job() - cancel pending jobs for the context
* @m2m_ctx: m2m context with jobs to be canceled
@ -421,7 +438,12 @@ void v4l2_m2m_job_finish(struct v4l2_m2m_dev *m2m_dev,
/* This instance might have more buffers ready, but since we do not
* allow more than one job on the job_queue per instance, each has
* to be scheduled separately after the previous one finishes. */
v4l2_m2m_try_schedule(m2m_ctx);
__v4l2_m2m_try_queue(m2m_dev, m2m_ctx);
/* We might be running in atomic context,
* but the job must be run in non-atomic context.
*/
schedule_work(&m2m_dev->job_work);
}
EXPORT_SYMBOL(v4l2_m2m_job_finish);
@ -863,6 +885,7 @@ struct v4l2_m2m_dev *v4l2_m2m_init(const struct v4l2_m2m_ops *m2m_ops)
m2m_dev->m2m_ops = m2m_ops;
INIT_LIST_HEAD(&m2m_dev->job_queue);
spin_lock_init(&m2m_dev->job_spinlock);
INIT_WORK(&m2m_dev->job_work, v4l2_m2m_device_run_work);
return m2m_dev;
}