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Message-Id: <20240420-bpf_wq-v2-0-6c986a5a741f@kernel.org>
Date: Sat, 20 Apr 2024 11:09:00 +0200
From: Benjamin Tissoires <bentiss@...nel.org>
To: Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>, Andrii Nakryiko <andrii@...nel.org>,
Martin KaFai Lau <martin.lau@...ux.dev>,
Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>,
Yonghong Song <yonghong.song@...ux.dev>,
John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>,
Stanislav Fomichev <sdf@...gle.com>, Hao Luo <haoluo@...gle.com>,
Jiri Olsa <jolsa@...nel.org>, Mykola Lysenko <mykolal@...com>,
Shuah Khan <shuah@...nel.org>
Cc: bpf@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-kselftest@...r.kernel.org, Benjamin Tissoires <bentiss@...nel.org>
Subject: [PATCH bpf-next v2 00/16] Introduce bpf_wq
This is a followup of sleepable bpf_timer[0].
When discussing sleepable bpf_timer, it was thought that we should give
a try to bpf_wq, as the 2 APIs are similar but distinct enough to
justify a new one.
So here it is.
I tried to keep as much as possible common code in kernel/bpf/helpers.c
but I couldn't get away with code duplication in kernel/bpf/verifier.c.
This series introduces a basic bpf_wq support:
- creation is supported
- assignment is supported
- running a simple bpf_wq is also supported.
We will probably need to extend the API further with:
- a full delayed_work API (can be piggy backed on top with a correct
flag)
- bpf_wq_cancel() <- apparently not, this is shooting ourself in the
foot
- bpf_wq_cancel_sync() (for sleepable programs)
- documentation
---
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@...nel.org>
To: Daniel Borkmann <daniel@...earbox.net>
To: Andrii Nakryiko <andrii@...nel.org>
To: Martin KaFai Lau <martin.lau@...ux.dev>
To: Eduard Zingerman <eddyz87@...il.com>
To: Song Liu <song@...nel.org>
To: Yonghong Song <yonghong.song@...ux.dev>
To: John Fastabend <john.fastabend@...il.com>
To: KP Singh <kpsingh@...nel.org>
To: Stanislav Fomichev <sdf@...gle.com>
To: Hao Luo <haoluo@...gle.com>
To: Jiri Olsa <jolsa@...nel.org>
To: Mykola Lysenko <mykolal@...com>
To: Shuah Khan <shuah@...nel.org>
Cc: <bpf@...r.kernel.org>
Cc: <linux-kernel@...r.kernel.org>
Cc: <linux-kselftest@...r.kernel.org>
Signed-off-by: Benjamin Tissoires <bentiss@...nel.org>
[0] https://lore.kernel.org/all/20240408-hid-bpf-sleepable-v6-0-0499ddd91b94@kernel.org/
---
Changes in v2:
- took previous review into account
- mainly dropped BPF_F_WQ_SLEEPABLE
- Link to v1: https://lore.kernel.org/r/20240416-bpf_wq-v1-0-c9e66092f842@kernel.org
---
Benjamin Tissoires (16):
bpf: make timer data struct more generic
bpf: replace bpf_timer_init with a generic helper
bpf: replace bpf_timer_set_callback with a generic helper
bpf: replace bpf_timer_cancel_and_free with a generic helper
bpf: add support for bpf_wq user type
tools: sync include/uapi/linux/bpf.h
bpf: verifier: bail out if the argument is not a map
bpf: add support for KF_ARG_PTR_TO_WORKQUEUE
bpf: allow struct bpf_wq to be embedded in arraymaps and hashmaps
selftests/bpf: add bpf_wq tests
bpf: wq: add bpf_wq_init
selftests/bpf: wq: add bpf_wq_init() checks
bpf: wq: add bpf_wq_set_callback_impl
selftests/bpf: add checks for bpf_wq_set_callback()
bpf: add bpf_wq_start
selftests/bpf: wq: add bpf_wq_start() checks
include/linux/bpf.h | 13 +-
include/linux/bpf_verifier.h | 1 +
include/uapi/linux/bpf.h | 4 +
kernel/bpf/arraymap.c | 18 +-
kernel/bpf/btf.c | 17 +
kernel/bpf/hashtab.c | 55 +++-
kernel/bpf/helpers.c | 348 ++++++++++++++++-----
kernel/bpf/syscall.c | 15 +-
kernel/bpf/verifier.c | 154 ++++++++-
tools/include/uapi/linux/bpf.h | 4 +
tools/testing/selftests/bpf/bpf_experimental.h | 7 +
.../selftests/bpf/bpf_testmod/bpf_testmod.c | 5 +
.../selftests/bpf/bpf_testmod/bpf_testmod_kfunc.h | 1 +
tools/testing/selftests/bpf/prog_tests/wq.c | 41 +++
tools/testing/selftests/bpf/progs/wq.c | 186 +++++++++++
tools/testing/selftests/bpf/progs/wq_failures.c | 144 +++++++++
16 files changed, 910 insertions(+), 103 deletions(-)
---
base-commit: ffa6b26b4d8a0520b78636ca9373ab842cb3b1a8
change-id: 20240411-bpf_wq-fe24e8d24f5e
Best regards,
--
Benjamin Tissoires <bentiss@...nel.org>
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