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Message-ID: <20230902115119.470238399@goodmis.org>
Date: Sat, 02 Sep 2023 07:50:42 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: linux-kernel@...r.kernel.org
Cc: Masami Hiramatsu <mhiramat@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Andrew Morton <akpm@...ux-foundation.org>,
stable@...r.kernel.org, Zheng Yejian <zhengyejian1@...wei.com>,
Brian Foster <bfoster@...hat.com>
Subject: [for-linus][PATCH 07/11] tracing: Zero the pipe cpumask on alloc to avoid spurious -EBUSY
From: Brian Foster <bfoster@...hat.com>
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@redhat.com
Cc: stable@...r.kernel.org
Fixes: c2489bb7e6be ("tracing: Introduce pipe_cpumask to avoid race on trace_pipes")
Reviewed-by: Zheng Yejian <zhengyejian1@...wei.com>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
Signed-off-by: Brian Foster <bfoster@...hat.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
---
kernel/trace/trace.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 23579fba1a57..35783a7baf15 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -9474,7 +9474,7 @@ static struct trace_array *trace_array_create(const char *name)
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;
@@ -10419,7 +10419,7 @@ __init static int tracer_alloc_buffers(void)
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 */
--
2.40.1
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