New version of the sleepable bpf_timer code, without the HID changes, as they can now go through the HID tree independantly.
For reference, the use cases I have in mind:
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Basically, I need to be able to defer a HID-BPF program for the following reasons (from the aforementioned patch): 1. defer an event: Sometimes we receive an out of proximity event, but the device can not be trusted enough, and we need to ensure that we won't receive another one in the following n milliseconds. So we need to wait those n milliseconds, and eventually re-inject that event in the stack.
2. inject new events in reaction to one given event: We might want to transform one given event into several. This is the case for macro keys where a single key press is supposed to send a sequence of key presses. But this could also be used to patch a faulty behavior, if a device forgets to send a release event.
3. communicate with the device in reaction to one event: We might want to communicate back to the device after a given event. For example a device might send us an event saying that it came back from sleeping state and needs to be re-initialized.
Currently we can achieve that by keeping a userspace program around, raise a bpf event, and let that userspace program inject the events and commands. However, we are just keeping that program alive as a daemon for just scheduling commands. There is no logic in it, so it doesn't really justify an actual userspace wakeup. So a kernel workqueue seems simpler to handle.
bpf_timers are currently running in a soft IRQ context, this patch series implements a sleppable context for them.
Cheers, Benjamin
To: Alexei Starovoitov ast@kernel.org To: Daniel Borkmann daniel@iogearbox.net To: Andrii Nakryiko andrii@kernel.org To: Martin KaFai Lau martin.lau@linux.dev To: Eduard Zingerman eddyz87@gmail.com To: Song Liu song@kernel.org To: Yonghong Song yonghong.song@linux.dev To: John Fastabend john.fastabend@gmail.com To: KP Singh kpsingh@kernel.org To: Stanislav Fomichev sdf@google.com To: Hao Luo haoluo@google.com To: Jiri Olsa jolsa@kernel.org To: Mykola Lysenko mykolal@fb.com To: Shuah Khan shuah@kernel.org Cc: Benjamin Tissoires bentiss@kernel.org Cc: bpf@vger.kernel.org Cc: linux-kernel@vger.kernel.org Cc: linux-kselftest@vger.kernel.org
--- Changes in v4: - dropped the HID changes, they can go independently from bpf-core - addressed Alexei's and Eduard's remarks - added selftests - Link to v3: https://lore.kernel.org/r/20240221-hid-bpf-sleepable-v3-0-1fb378ca6301@kerne...
Changes in v3: - fixed the crash from v2 - changed the API to have only BPF_F_TIMER_SLEEPABLE for bpf_timer_start() - split the new kfuncs/verifier patch into several sub-patches, for easier reviews - Link to v2: https://lore.kernel.org/r/20240214-hid-bpf-sleepable-v2-0-5756b054724d@kerne...
Changes in v2: - make use of bpf_timer (and dropped the custom HID handling) - implemented bpf_timer_set_sleepable_cb as a kfunc - still not implemented global subprogs - no sleepable bpf_timer selftests yet - Link to v1: https://lore.kernel.org/r/20240209-hid-bpf-sleepable-v1-0-4cc895b5adbd@kerne...
--- Benjamin Tissoires (6): bpf/helpers: introduce sleepable bpf_timers bpf/verifier: add bpf_timer as a kfunc capable type bpf/helpers: introduce bpf_timer_set_sleepable_cb() kfunc bpf/helpers: mark the callback of bpf_timer_set_sleepable_cb() as sleepable tools: sync include/uapi/linux/bpf.h selftests/bpf: add sleepable timer tests
include/linux/bpf_verifier.h | 1 + include/uapi/linux/bpf.h | 4 + kernel/bpf/helpers.c | 132 ++++++++++++++++++++- kernel/bpf/verifier.c | 92 +++++++++++++- tools/include/uapi/linux/bpf.h | 4 + tools/testing/selftests/bpf/bpf_experimental.h | 4 + .../selftests/bpf/bpf_testmod/bpf_testmod.c | 5 + .../selftests/bpf/bpf_testmod/bpf_testmod_kfunc.h | 1 + tools/testing/selftests/bpf/prog_tests/timer.c | 1 + tools/testing/selftests/bpf/progs/timer.c | 40 ++++++- tools/testing/selftests/bpf/progs/timer_failure.c | 114 +++++++++++++++++- 11 files changed, 387 insertions(+), 11 deletions(-) --- base-commit: 9187210eee7d87eea37b45ea93454a88681894a4 change-id: 20240205-hid-bpf-sleepable-c01260fd91c4
Best regards,