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bpf: Introduce bpf_timer_cancel_async() kfunc

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

Co-developed-by: Mykyta Yatsenko <yatsenko@meta.com>
Signed-off-by: Mykyta Yatsenko <yatsenko@meta.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20260201025403.66625-4-alexei.starovoitov@gmail.com
This commit is contained in:
Alexei Starovoitov
2026-01-31 18:53:57 -08:00
committed by Andrii Nakryiko
parent 19bd300e22
commit a7e172aa4c
1 changed files with 48 additions and 0 deletions
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48
kernel/bpf/helpers.c
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@@ -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 = {