Commit a7e172aa authored by Alexei Starovoitov's avatar Alexei Starovoitov Committed by Andrii Nakryiko
Browse files

bpf: Introduce bpf_timer_cancel_async() kfunc 



Introduce bpf_timer_cancel_async() that wraps hrtimer_try_to_cancel()
and executes it either synchronously or defers to irq_work.

Co-developed-by: default avatarMykyta Yatsenko <yatsenko@meta.com>
Signed-off-by: default avatarMykyta Yatsenko <yatsenko@meta.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20260201025403.66625-4-alexei.starovoitov@gmail.com
parent 19bd300e

kernel/bpf/helpers.c

+48 −0
Original line number Diff line number Diff line
@@ -4426,6 +4426,53 @@ __bpf_kfunc int bpf_dynptr_file_discard(struct bpf_dynptr *dynptr) 
	return 0;

}



/**

 * bpf_timer_cancel_async - try to deactivate a timer

 * @timer:	bpf_timer to stop

 *

 * Returns:

 *

 *  *  0 when the timer was not active

 *  *  1 when the timer was active

 *  * -1 when the timer is currently executing the callback function and

 *       cannot be stopped

 *  * -ECANCELED when the timer will be cancelled asynchronously

 *  * -ENOMEM when out of memory

 *  * -EINVAL when the timer was not initialized

 *  * -ENOENT when this kfunc is racing with timer deletion

 */

__bpf_kfunc int bpf_timer_cancel_async(struct bpf_timer *timer)

{

	struct bpf_async_kern *async = (void *)timer;

	struct bpf_async_cb *cb;

	int ret;



	cb = READ_ONCE(async->cb);

	if (!cb)

		return -EINVAL;



	/*

	 * Unlike hrtimer_start() it's ok to synchronously call

	 * hrtimer_try_to_cancel() when refcnt reached zero, but deferring to

	 * irq_work is not, since irq callback may execute after RCU GP and

	 * cb could be freed at that time. Check for refcnt zero for

	 * consistency.

	 */

	if (!refcount_inc_not_zero(&cb->refcnt))

		return -ENOENT;



	if (!in_hardirq()) {

		struct bpf_hrtimer *t = container_of(cb, struct bpf_hrtimer, cb);



		ret = hrtimer_try_to_cancel(&t->timer);

		bpf_async_refcount_put(cb);

		return ret;

	} else {

		ret = bpf_async_schedule_op(cb, BPF_ASYNC_CANCEL, 0, 0);

		return ret ? ret : -ECANCELED;

	}

}



__bpf_kfunc_end_defs();



static void bpf_task_work_cancel_scheduled(struct irq_work *irq_work)
@@ -4609,6 +4656,7 @@ BTF_ID_FLAGS(func, bpf_task_work_schedule_signal, KF_IMPLICIT_ARGS) 
BTF_ID_FLAGS(func, bpf_task_work_schedule_resume, KF_IMPLICIT_ARGS)

BTF_ID_FLAGS(func, bpf_dynptr_from_file)

BTF_ID_FLAGS(func, bpf_dynptr_file_discard)

BTF_ID_FLAGS(func, bpf_timer_cancel_async)

BTF_KFUNCS_END(common_btf_ids)



static const struct btf_kfunc_id_set common_kfunc_set = {