linux-kernel - [PATCH] ring-buffer: Avoid softlockup in ring_buffer

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Date:   Wed, 6 Sep 2023 16:19:30 +0800
From:   Zheng Yejian <zhengyejian1@...wei.com>
To:     <rostedt@...dmis.org>, <mhiramat@...nel.org>
CC:     <linux-kernel@...r.kernel.org>,
        <linux-trace-kernel@...r.kernel.org>, <yeweihua4@...wei.com>,
        <zhengyejian1@...wei.com>
Subject: [PATCH] ring-buffer: Avoid softlockup in ring_buffer_resize()

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.

Signed-off-by: Zheng Yejian <zhengyejian1@...wei.com>
---
 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 78502d4c7214..72ccf75defd0 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -2198,6 +2198,8 @@ int ring_buffer_resize(struct trace_buffer *buffer, unsigned long size,
 				err = -ENOMEM;
 				goto out_err;
 			}
+
+			cond_resched();
 		}

 		cpus_read_lock();
-- 
2.25.1