Re: [PATCH v4 05/12] perf record: start threads in the beginning of trace streaming

[Andi Kleen]

> +	err = write(thread->pipes.ack[1], &msg, sizeof(msg));
> +	if (err == -1)
> +		pr_err("threads[%d]: failed to notify on start. Error %m", thread->tid);

It might be safer to not use %m. I'm not sure if all the non glibc
libcs that people use support it.