linux-kernel - [PATCH bpf-next] bpf: Remove preempt_disable in bpf_try_get

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Message-ID: <20250819125638.2544715-1-chen.dylane@linux.dev>
Date: Tue, 19 Aug 2025 20:56:38 +0800
From: Tao Chen <chen.dylane@...ux.dev>
To: ast@...nel.org,
	daniel@...earbox.net,
	andrii@...nel.org,
	martin.lau@...ux.dev,
	eddyz87@...il.com,
	song@...nel.org,
	yonghong.song@...ux.dev,
	john.fastabend@...il.com,
	kpsingh@...nel.org,
	sdf@...ichev.me,
	haoluo@...gle.com,
	jolsa@...nel.org
Cc: bpf@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Tao Chen <chen.dylane@...ux.dev>
Subject: [PATCH bpf-next] bpf: Remove preempt_disable in bpf_try_get_buffers

Now BPF program will run with migration disabled, so it is safe
to access this_cpu_inc_return(bpf_bprintf_nest_level).

Fixes: d9c9e4db186a ("bpf: Factorize bpf_trace_printk and bpf_seq_printf")
Signed-off-by: Tao Chen <chen.dylane@...ux.dev>
---
 kernel/bpf/helpers.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 6b4877e85a6..182886585d4 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -774,11 +774,9 @@ int bpf_try_get_buffers(struct bpf_bprintf_buffers **bufs)
 {
 	int nest_level;
 
-	preempt_disable();
 	nest_level = this_cpu_inc_return(bpf_bprintf_nest_level);
 	if (WARN_ON_ONCE(nest_level > MAX_BPRINTF_NEST_LEVEL)) {
 		this_cpu_dec(bpf_bprintf_nest_level);
-		preempt_enable();
 		return -EBUSY;
 	}
 	*bufs = this_cpu_ptr(&bpf_bprintf_bufs[nest_level - 1]);
@@ -791,7 +789,6 @@ void bpf_put_buffers(void)
 	if (WARN_ON_ONCE(this_cpu_read(bpf_bprintf_nest_level) == 0))
 		return;
 	this_cpu_dec(bpf_bprintf_nest_level);
-	preempt_enable();
 }
 
 void bpf_bprintf_cleanup(struct bpf_bprintf_data *data)
-- 
2.48.1