From cbd9463da1b12cdf9aa79e7cf470431d39131fca Mon Sep 17 00:00:00 2001 From: Ezequiel Garcia Date: Thu, 18 Oct 2018 14:02:23 -0400 Subject: [PATCH] media: v4l2-mem2mem: Avoid calling .device_run in v4l2_m2m_job_finish 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 Signed-off-by: Hans Verkuil Signed-off-by: Mauro Carvalho Chehab --- drivers/media/v4l2-core/v4l2-mem2mem.c | 25 ++++++++++++++++++++++++- 1 file changed, 24 insertions(+), 1 deletion(-) diff --git a/drivers/media/v4l2-core/v4l2-mem2mem.c b/drivers/media/v4l2-core/v4l2-mem2mem.c index 2307fcc663ec..5bbdec55b7d7 100644 --- a/drivers/media/v4l2-core/v4l2-mem2mem.c +++ b/drivers/media/v4l2-core/v4l2-mem2mem.c @@ -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; } -- 2.45.2