New version of the sleepable bpf_timer code. I'm posting this as this is the result of the previous review, so we can have a baseline to compare to. The plan is now to introduce a new user API struct bpf_wq, as the timer API working on softIRQ seems to be quite far away from a wq. For reference, the use cases I have in mind: --- 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@xxxxxxxxxx> To: Daniel Borkmann <daniel@xxxxxxxxxxxxx> To: Andrii Nakryiko <andrii@xxxxxxxxxx> To: Martin KaFai Lau <martin.lau@xxxxxxxxx> To: Eduard Zingerman <eddyz87@xxxxxxxxx> To: Song Liu <song@xxxxxxxxxx> To: Yonghong Song <yonghong.song@xxxxxxxxx> To: John Fastabend <john.fastabend@xxxxxxxxx> To: KP Singh <kpsingh@xxxxxxxxxx> To: Stanislav Fomichev <sdf@xxxxxxxxxx> To: Hao Luo <haoluo@xxxxxxxxxx> To: Jiri Olsa <jolsa@xxxxxxxxxx> To: Mykola Lysenko <mykolal@xxxxxx> To: Shuah Khan <shuah@xxxxxxxxxx> Cc: Benjamin Tissoires <bentiss@xxxxxxxxxx> Cc: <bpf@xxxxxxxxxxxxxxx> Cc: <linux-kernel@xxxxxxxxxxxxxxx> Cc: <linux-kselftest@xxxxxxxxxxxxxxx> --- Changes in v6: - Use of a workqueue to clean up sleepable timers - integrated Kumar's patch instead of mine - Link to v5: https://lore.kernel.org/r/20240322-hid-bpf-sleepable-v5-0-179c7b59eaaa@xxxxxxxxxx Changes in v5: - took various reviews into account - rewrote the tests to be separated to not have a uggly include - Link to v4: https://lore.kernel.org/r/20240315-hid-bpf-sleepable-v4-0-5658f2540564@xxxxxxxxxx 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@xxxxxxxxxx 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@xxxxxxxxxx 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@xxxxxxxxxx --- Benjamin Tissoires (5): bpf/helpers: introduce sleepable bpf_timers 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 Kumar Kartikeya Dwivedi (1): bpf: Add support for KF_ARG_PTR_TO_TIMER include/linux/bpf_verifier.h | 1 + include/uapi/linux/bpf.h | 13 ++ kernel/bpf/helpers.c | 202 ++++++++++++++++--- kernel/bpf/verifier.c | 98 +++++++++- tools/include/uapi/linux/bpf.h | 20 +- tools/testing/selftests/bpf/bpf_experimental.h | 5 + .../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 | 34 ++++ .../testing/selftests/bpf/progs/timer_sleepable.c | 213 +++++++++++++++++++++ 10 files changed, 553 insertions(+), 39 deletions(-) --- base-commit: 61df575632d6b39213f47810c441bddbd87c3606 change-id: 20240205-hid-bpf-sleepable-c01260fd91c4 Best regards, -- Benjamin Tissoires <bentiss@xxxxxxxxxx>
