Commit 7e792d39 authored by Hou Tao's avatar Hou Tao Committed by Xiaomeng Zhang
Browse files

bpf: Use preempt_count() directly in bpf_send_signal_common() 

maillist inclusion
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/IBQWD8

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git/commit/?id=b4a8b5bba712



--------------------------------

bpf_send_signal_common() uses preemptible() to check whether or not the
current context is preemptible. If it is preemptible, it will use
irq_work to send the signal asynchronously instead of trying to hold a
spin-lock, because spin-lock is sleepable under PREEMPT_RT.

However, preemptible() depends on CONFIG_PREEMPT_COUNT. When
CONFIG_PREEMPT_COUNT is turned off (e.g., CONFIG_PREEMPT_VOLUNTARY=y),
!preemptible() will be evaluated as 1 and bpf_send_signal_common() will
use irq_work unconditionally.

Fix it by unfolding "!preemptible()" and using "preempt_count() != 0 ||
irqs_disabled()" instead.

Fixes: 87c544108b61 ("bpf: Send signals asynchronously if !preemptible")
Signed-off-by: default avatarHou Tao <houtao1@huawei.com>
Link: https://lore.kernel.org/r/20250220042259.1583319-1-houtao@huaweicloud.com


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatarXiaomeng Zhang <zhangxiaomeng13@huawei.com&gt;z>
parent 9d87efb3

kernel/trace/bpf_trace.c

+1 −1
Original line number Diff line number Diff line
@@ -1081,7 +1081,7 @@ static int bpf_send_signal_common(u32 sig, enum pid_type type) 
	if (unlikely(is_global_init(current)))

		return -EPERM;



	if (!preemptible()) {

	if (preempt_count() != 0 || irqs_disabled()) {

		/* Do an early check on signal validity. Otherwise,

		 * the error is lost in deferred irq_work.

		 */