On Fri, 1 Sep 2023 15:26:26 +0800
Chuang Wang <nashuiliang@xxxxxxxxx> wrote:
> There is a problem in the linux-6.5 when I execute the following
> command:
>
> $ perf ftrace -t irqsoff
> failed to open trace_pipe
>
> At the same time, when I open this file, the same error occurs.
>
> Therefore, after carefully looking at the code, the open function of
> 'trace_pipe' returns -EBUSY in open_pipe_on_cpu() because no clearing
> operation was performed when 'trace_array->pipe_cpumask' was allocated.
>
> With this patch, Use zalloc_cpumask_var() to ensure that
> 'trace_array->pipe_cpumask' is reset to 0 when allocated.
Good catch. This looks good to me.
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
>
> Cc: stable@xxxxxxxxxxxxxxx
> Fixes: c2489bb7e6be ("tracing: Introduce pipe_cpumask to avoid race on trace_pipes")
> Signed-off-by: Chuang Wang <nashuiliang@xxxxxxxxx>
> ---
> 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 d8233d34b5a0..c0b8a72f3466 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -9461,7 +9461,7 @@ 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;
> @@ -10406,7 +10406,7 @@ __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 */
> --
> 2.39.2
>
--
Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
