Re: [PATCH] tracing: Wait for marker writers when copy_trace_marker is cleared

[Masami Hiramatsu (Google)]

On Sat,  7 Nov 2026 19:07:22 +0800, Pengfei Li <ljdlns1987@xxxxxxxxx> wrote:
> Clearing copy_trace_marker removes the instance from marker_copies
> without waiting for trace_marker writers still walking the list. If the
> option is set again right away, a writer on that entry can revisit
> instances and write the same marker twice.
> 
> Fixes: 7b382efd5e8a ("tracing: Allow the top level trace_marker to write into another instances")
> Assisted-by: LLM
> Signed-off-by: Pengfei Li <lipengfei28@xxxxxxxxxx>

Looks good to me.

Reviewed-by: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>

Thanks,

> ---
>  kernel/trace/trace.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index 18710c190c92..b0357f1b5a69 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -4016,7 +4016,9 @@ int set_tracer_flag(struct trace_array *tr, u64 mask, int enabled)
>  		break;
>  
>  	case TRACE_ITER(COPY_MARKER):
> -		update_marker_trace(tr, enabled);
> +		/* Writers of the top level trace_marker may still be on this instance */
> +		if (update_marker_trace(tr, enabled) && !enabled)
> +			synchronize_rcu();
>  		/* update_marker_trace updates the tr->trace_flags */
>  		return 0;
>  	}
> 
> base-commit: 4539944e515183668109bdf4d0c3d7d228383d88
> -- 
> 2.34.1
> 
>

-- 
Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>