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.
Testing -------
In order to test the change, and make sure no regressions are introduced, a kselftest test is added to stress the mem2mem framework.
Note that this series rework the kselftest media_tests target. Those tests that need hardware and human intervention are now marked as _EXTENDED, and a frontend script is added to run those tests that can run without hardware or human intervention.
This will allow the media_tests target to be included in automatic regression testing setups.
Hopefully, we will be able to introduce more and more automatic regression tests. Currently, our self-test run looks like:
$ make TARGETS=media_tests kselftest make[1]: Entering directory '/home/zeta/repos/builds/virtme-x86_64' make[3]: warning: jobserver unavailable: using -j1. Add '+' to parent make rule. make[3]: Nothing to be done for 'all'. make[3]: warning: jobserver unavailable: using -j1. Add '+' to parent make rule. TAP version 13 selftests: media_tests: m2m_job_test.sh ======================================== ------------------- running media tests ------------------- media_device : no video4linux drivers loaded, vim2m is needed not ok 1..1 selftests: media_tests: m2m_job_test.sh [SKIP] make[1]: Leaving directory '/home/zeta/repos/builds/virtme-x86_64'
Ezequiel Garcia (3): 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 | 72 +++-- .../testing/selftests/media_tests/.gitignore | 1 + tools/testing/selftests/media_tests/Makefile | 5 +- .../selftests/media_tests/m2m_job_test.c | 287 ++++++++++++++++++ .../selftests/media_tests/m2m_job_test.sh | 32 ++ 5 files changed, 371 insertions(+), 26 deletions(-) create mode 100644 tools/testing/selftests/media_tests/m2m_job_test.c create mode 100755 tools/testing/selftests/media_tests/m2m_job_test.sh