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| author | Brian Foster <bfoster@redhat.com> | 2023-08-31 08:55:00 -0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2023-09-13 09:43:05 +0200 |
| commit | 1dd387668d5bd911df0b21716fff6f5180b11e42 (patch) | |
| tree | ffb257b6a1f0e0bcc541db50ec1feac7ecc78c4a | |
| parent | e43a7ae58d003a93b1adcabfd7e0a1f81472c4cf (diff) | |
| download | linux-stable-1dd387668d5bd911df0b21716fff6f5180b11e42.tar.gz linux-stable-1dd387668d5bd911df0b21716fff6f5180b11e42.tar.bz2 linux-stable-1dd387668d5bd911df0b21716fff6f5180b11e42.zip | |
tracing: Zero the pipe cpumask on alloc to avoid spurious -EBUSY
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@redhat.com
Cc: stable@vger.kernel.org
Fixes: c2489bb7e6be ("tracing: Introduce pipe_cpumask to avoid race on trace_pipes")
Reviewed-by: Zheng Yejian <zhengyejian1@huawei.com>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | kernel/trace/trace.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 5d0465ae7be8..54ccdca39531 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -9395,7 +9395,7 @@ 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; @@ -10267,7 +10267,7 @@ __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 */ |