This series goal is to avoid drivers from having ad-hoc code to call .device_run in non-atomic context. Currently, .device_run can be called via v4l2_m2m_job_finish(), potentially running in interrupt context.
This series will be useful for the upcoming Request API, where drivers typically require .device_run to be called in non-atomic context for v4l2_ctrl_request_setup() calls.
The solution is to add a per-device worker that is scheduled by v4l2_m2m_job_finish, which replaces drivers having a threaded interrupt or similar.
This change allows v4l2_m2m_job_finish() to be called in interrupt context, separating .device_run and v4l2_m2m_job_finish() contexts.
It's worth mentioning that v4l2_m2m_cancel_job() doesn't need to flush or cancel the new worker, because the job_spinlock synchronizes both and also because the core prevents simultaneous jobs. Either v4l2_m2m_cancel_job() will wait for the worker, or the worker will be unable to run a new job.
While working on this series, I found a bug recently introduced on commit "media: mem2mem: Remove excessive try_run call". The first patch fixes the bug.
In order to test the change, and make sure no regressions are introduced, a kselftest test is added to stress the mem2mem framework.
Patches are based on v4.18-rc4 plus:
34dbb848d5e47 "media: mem2mem: Remove excessive try_run call"
Ezequiel Garcia (4): v4l2-mem2mem: Fix missing v4l2_m2m_try_run call v4l2-mem2mem: Avoid v4l2_m2m_prepare_buf from scheduling a job v4l2-mem2mem: Avoid calling .device_run in v4l2_m2m_job_finish selftests: media_tests: Add a memory-to-memory concurrent stress test
Sakari Ailus (1): v4l2-mem2mem: Simplify exiting the function in __v4l2_m2m_try_schedule
drivers/media/v4l2-core/v4l2-mem2mem.c | 104 +++++-- tools/testing/selftests/media_tests/Makefile | 4 +- .../selftests/media_tests/m2m_job_test.c | 283 ++++++++++++++++++ 3 files changed, 362 insertions(+), 29 deletions(-) create mode 100644 tools/testing/selftests/media_tests/m2m_job_test.c