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Benjamin Tissoires says: ==================== 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 [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 ==================== Link: https://lore.kernel.org/r/20240420-bpf_wq-v2-0-6c986a5a741f@kernel.org Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.