linux-kernel - [PATCH AUTOSEL 5.4 6/7] ring-buffer: Avoid softlockup in ring_buffer

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Message-Id: <20230924132015.1276811-6-sashal@kernel.org>
Date:   Sun, 24 Sep 2023 09:20:13 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Zheng Yejian <zhengyejian1@...wei.com>, mhiramat@...nel.org,
        Steven Rostedt <rostedt@...dmis.org>,
        Sasha Levin <sashal@...nel.org>,
        linux-trace-kernel@...r.kernel.org
Subject: [PATCH AUTOSEL 5.4 6/7] ring-buffer: Avoid softlockup in ring_buffer_resize()

From: Zheng Yejian <zhengyejian1@...wei.com>

[ Upstream commit f6bd2c92488c30ef53b5bd80c52f0a7eee9d545a ]

When user resize all trace ring buffer through file 'buffer_size_kb',
then in ring_buffer_resize(), kernel allocates buffer pages for each
cpu in a loop.

If the kernel preemption model is PREEMPT_NONE and there are many cpus
and there are many buffer pages to be allocated, it may not give up cpu
for a long time and finally cause a softlockup.

To avoid it, call cond_resched() after each cpu buffer allocation.

Link: https://lore.kernel.org/linux-trace-kernel/20230906081930.3939106-1-zhengyejian1@huawei.com

Cc: <mhiramat@...nel.org>
Signed-off-by: Zheng Yejian <zhengyejian1@...wei.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 kernel/trace/ring_buffer.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 445475c229b3a..2a4fb4f1e3cad 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -1821,6 +1821,8 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size,
 				err = -ENOMEM;
 				goto out_err;
 			}
+
+			cond_resched();
 		}
 
 		get_online_cpus();
-- 
2.40.1