This is a note to let you know that I've just added the patch titled
ring-buffer: use READ_ONCE() to read cpu_buffer->commit_page in concurrent environment
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
ring-buffer-use-read_once-to-read-cpu_buffer-commit_.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 99e144ff7837af75ef05a020b17b9857d52c185a
Author: linke li <lilinke99@xxxxxx>
Date: Sat Mar 2 12:42:21 2024 +0800
ring-buffer: use READ_ONCE() to read cpu_buffer->commit_page in concurrent environment
[ Upstream commit f1e30cb6369251c03f63c564006f96a54197dcc4 ]
In function ring_buffer_iter_empty(), cpu_buffer->commit_page is read
while other threads may change it. It may cause the time_stamp that read
in the next line come from a different page. Use READ_ONCE() to avoid
having to reason about compiler optimizations now and in future.
Link: https://lore.kernel.org/linux-trace-kernel/tencent_DFF7D3561A0686B5E8FC079150A02505180A@xxxxxx
Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
Signed-off-by: linke li <lilinke99@xxxxxx>
Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 80ec515ae81e7..c6bcb80785d8f 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -4390,7 +4390,7 @@ int ring_buffer_iter_empty(struct ring_buffer_iter *iter)
cpu_buffer = iter->cpu_buffer;
reader = cpu_buffer->reader_page;
head_page = cpu_buffer->head_page;
- commit_page = cpu_buffer->commit_page;
+ commit_page = READ_ONCE(cpu_buffer->commit_page);
commit_ts = commit_page->page->time_stamp;
/*
