From: Mykyta Yatsenko <yatsenko@xxxxxxxx> This patch introduces a new mechanism for BPF programs to schedule deferred execution in the context of a specific task using the kernel’s task_work infrastructure. The new bpf_task_work interface enables BPF use cases that require sleepable subprogram execution within task context, for example, scheduling sleepable function from the context that does not allow sleepable, such as NMI. Introduced kfuncs bpf_task_work_schedule_signal() and bpf_task_work_schedule_resume() for scheduling BPF callbacks correspond to different modes used by task_work (TWA_SIGNAL or TWA_RESUME). The implementation manages scheduling state via metadata objects (struct bpf_task_work_context). Pointers to bpf_task_work_context are stored in BPF map values. State transitions are handled via an atomic state machine (bpf_task_work_state) to ensure correctness under concurrent usage and deletion, lifetime is guarded by refcounting and RCU Tasks Trace. Kfuncs call task_work_add() indirectly via irq_work to avoid locking in potentially NMI context. v2 -> v3 * Introduce ref counting * Add patches with minor verifier and btf.c refactorings to avoid code duplication * Rework initiation of the task work scheduling to handle race with map usercnt dropping to zero Mykyta Yatsenko (7): bpf: refactor special field-type detection bpf: extract generic helper from process_timer_func() bpf: htab: extract helper for freeing special structs bpf: bpf task work plumbing bpf: extract map key pointer calculation bpf: task work scheduling kfuncs selftests/bpf: BPF task work scheduling tests include/linux/bpf.h | 11 + include/uapi/linux/bpf.h | 4 + kernel/bpf/arraymap.c | 8 +- kernel/bpf/btf.c | 63 ++- kernel/bpf/hashtab.c | 43 +- kernel/bpf/helpers.c | 386 +++++++++++++++++- kernel/bpf/syscall.c | 16 +- kernel/bpf/verifier.c | 136 +++++- tools/include/uapi/linux/bpf.h | 4 + .../selftests/bpf/prog_tests/test_task_work.c | 149 +++++++ tools/testing/selftests/bpf/progs/task_work.c | 108 +++++ .../selftests/bpf/progs/task_work_fail.c | 98 +++++ 12 files changed, 932 insertions(+), 94 deletions(-) create mode 100644 tools/testing/selftests/bpf/prog_tests/test_task_work.c create mode 100644 tools/testing/selftests/bpf/progs/task_work.c create mode 100644 tools/testing/selftests/bpf/progs/task_work_fail.c -- 2.51.0
