This is a note to let you know that I've just added the patch titled
tracing: Zero the pipe cpumask on alloc to avoid spurious -EBUSY
to the 6.4-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:
tracing-zero-the-pipe-cpumask-on-alloc-to-avoid-spurious-ebusy.patch
and it can be found in the queue-6.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 3d07fa1dd19035eb0b13ae6697efd5caa9033e74 Mon Sep 17 00:00:00 2001
From: Brian Foster <bfoster@xxxxxxxxxx>
Date: Thu, 31 Aug 2023 08:55:00 -0400
Subject: tracing: Zero the pipe cpumask on alloc to avoid spurious -EBUSY
From: Brian Foster <bfoster@xxxxxxxxxx>
commit 3d07fa1dd19035eb0b13ae6697efd5caa9033e74 upstream.
The pipe cpumask used to serialize opens between the main and percpu
trace pipes is not zeroed or initialized. This can result in
spurious -EBUSY returns if underlying memory is not fully zeroed.
This has been observed by immediate failure to read the main
trace_pipe file on an otherwise newly booted and idle system:
# cat /sys/kernel/debug/tracing/trace_pipe
cat: /sys/kernel/debug/tracing/trace_pipe: Device or resource busy
Zero the allocation of pipe_cpumask to avoid the problem.
Link: https://lore.kernel.org/linux-trace-kernel/20230831125500.986862-1-bfoster@xxxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx
Fixes: c2489bb7e6be ("tracing: Introduce pipe_cpumask to avoid race on trace_pipes")
Reviewed-by: Zheng Yejian <zhengyejian1@xxxxxxxxxx>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
Signed-off-by: Brian Foster <bfoster@xxxxxxxxxx>
Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/trace/trace.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -9465,7 +9465,7 @@ static struct trace_array *trace_array_c
if (!alloc_cpumask_var(&tr->tracing_cpumask, GFP_KERNEL))
goto out_free_tr;
- if (!alloc_cpumask_var(&tr->pipe_cpumask, GFP_KERNEL))
+ if (!zalloc_cpumask_var(&tr->pipe_cpumask, GFP_KERNEL))
goto out_free_tr;
tr->trace_flags = global_trace.trace_flags & ~ZEROED_TRACE_FLAGS;
@@ -10410,7 +10410,7 @@ __init static int tracer_alloc_buffers(v
if (trace_create_savedcmd() < 0)
goto out_free_temp_buffer;
- if (!alloc_cpumask_var(&global_trace.pipe_cpumask, GFP_KERNEL))
+ if (!zalloc_cpumask_var(&global_trace.pipe_cpumask, GFP_KERNEL))
goto out_free_savedcmd;
/* TODO: make the number of buffers hot pluggable with CPUS */
Patches currently in stable-queue which might be from bfoster@xxxxxxxxxx are
queue-6.4/tracing-zero-the-pipe-cpumask-on-alloc-to-avoid-spurious-ebusy.patch
