Commit 34dbb848d5e4 ("media: mem2mem: Remove excessive try_run call")
removed a redundant call to v4l2_m2m_try_run but instead introduced
a bug. Consider the following case:
1) Context A schedules, queues and runs job A.
2) While the m2m device is running, context B schedules
and queues job B. Job B cannot run, because it has to
wait for job A.
3) Job A completes, calls v4l2_m2m_job_finish, and tries
to queue a job for context A, but since the context is
empty it won't do anything.
In this scenario, queued job B will never run. Fix this by calling
v4l2_m2m_try_run from v4l2_m2m_try_schedule.
While here, add more documentation to these functions.
Fixes: 34dbb848d5e4 ("media: mem2mem: Remove excessive try_run call")
Signed-off-by: Ezequiel Garcia <ezequiel@xxxxxxxxxxxxx>
---
drivers/media/v4l2-core/v4l2-mem2mem.c | 32 +++++++++++++++++++++++---
1 file changed, 29 insertions(+), 3 deletions(-)
diff --git a/drivers/media/v4l2-core/v4l2-mem2mem.c b/drivers/media/v4l2-core/v4l2-mem2mem.c
index 5f9cd5b74cda..dfd796621b06 100644
--- a/drivers/media/v4l2-core/v4l2-mem2mem.c
+++ b/drivers/media/v4l2-core/v4l2-mem2mem.c
@@ -209,15 +209,23 @@ static void v4l2_m2m_try_run(struct v4l2_m2m_dev *m2m_dev)
m2m_dev->curr_ctx->job_flags |= TRANS_RUNNING;
spin_unlock_irqrestore(&m2m_dev->job_spinlock, flags);
+ dprintk("Running job on m2m_ctx: %p\n", m2m_dev->curr_ctx);
m2m_dev->m2m_ops->device_run(m2m_dev->curr_ctx->priv);
}
-void v4l2_m2m_try_schedule(struct v4l2_m2m_ctx *m2m_ctx)
+/*
+ * __v4l2_m2m_try_queue() - queue a job
+ * @m2m_dev: m2m device
+ * @m2m_ctx: m2m context
+ *
+ * Check if this context is ready to queue a job.
+ *
+ * This function can run in interrupt context.
+ */
+static void __v4l2_m2m_try_queue(struct v4l2_m2m_dev *m2m_dev, struct v4l2_m2m_ctx *m2m_ctx)
{
- struct v4l2_m2m_dev *m2m_dev;
unsigned long flags_job, flags_out, flags_cap;
- m2m_dev = m2m_ctx->m2m_dev;
dprintk("Trying to schedule a job for m2m_ctx: %p\n", m2m_ctx);
if (!m2m_ctx->out_q_ctx.q.streaming
@@ -275,7 +283,25 @@ void v4l2_m2m_try_schedule(struct v4l2_m2m_ctx *m2m_ctx)
m2m_ctx->job_flags |= TRANS_QUEUED;
spin_unlock_irqrestore(&m2m_dev->job_spinlock, flags_job);
+}
+
+/**
+ * v4l2_m2m_try_schedule() - schedule and possibly run a job for any context
+ * @m2m_ctx: m2m context
+ *
+ * Check if this context is ready to queue a job. If suitable,
+ * run the next queued job on the mem2mem device.
+ *
+ * This function shouldn't run in interrupt context.
+ *
+ * Note that v4l2_m2m_try_schedule() can schedule one job for this context,
+ * and then run another job for another context.
+ */
+void v4l2_m2m_try_schedule(struct v4l2_m2m_ctx *m2m_ctx)
+{
+ struct v4l2_m2m_dev *m2m_dev = m2m_ctx->m2m_dev;
+ __v4l2_m2m_try_queue(m2m_dev, m2m_ctx);
v4l2_m2m_try_run(m2m_dev);
}
EXPORT_SYMBOL_GPL(v4l2_m2m_try_schedule);
--
2.18.0
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