From: Zheng Yejian <zhengyejian1@huawei.com>
Date: Wed, 6 Sep 2023 08:19:30 +0000 (+0800)
Subject: ring-buffer: Avoid softlockup in ring_buffer_resize()
X-Git-Tag: v6.6-rc2~33^2~9
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=f6bd2c92488c30ef53b5bd80c52f0a7eee9d545a;p=thirdparty%2Fkernel%2Flinux.git

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.

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

Cc: <mhiramat@kernel.org>
Signed-off-by: Zheng Yejian <zhengyejian1@huawei.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 78502d4c7214e..72ccf75defd0f 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();