Re: [PATCH 07/10] rt-utils: Decouple writting trace-marks with trace stopping

[John Kacur <jkacur@redhat.com>]

On Wed, 3 Sep 2025, Sebastian Andrzej Siewior wrote:

> Most users write a trace mark and expect that the trace stops afterwads.
> Decoupling writting and stopping the trace so it can be used in context
> where trace stopping is not needed.
> 
> Make tracemark() writting just to the tracemark file.
> Add tracing_stop() which stops tracing and let current users of
> tracemark() use it.
> 
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> ---
>  src/cyclictest/cyclictest.c         | 1 +
>  src/include/rt-utils.h              | 1 +
>  src/lib/rt-utils.c                  | 8 ++++++--
>  src/oslat/oslat.c                   | 1 +
>  src/sched_deadline/cyclicdeadline.c | 1 +
>  5 files changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/src/cyclictest/cyclictest.c b/src/cyclictest/cyclictest.c
> index 890da5d869c92..b4bce8915b432 100644
> --- a/src/cyclictest/cyclictest.c
> +++ b/src/cyclictest/cyclictest.c
> @@ -852,6 +852,7 @@ static void *timerthread(void *param)
>  				break_thread_id = stat->tid;
>  				tracemark("hit latency threshold (%llu > %d)",
>  					  (unsigned long long) diff, tracelimit);
> +				tracing_stop();
>  				break_thread_value = diff;
>  			}
>  			pthread_mutex_unlock(&break_thread_id_lock);
> diff --git a/src/include/rt-utils.h b/src/include/rt-utils.h
> index 569023c5d3051..e148dd77fd7d8 100644
> --- a/src/include/rt-utils.h
> +++ b/src/include/rt-utils.h
> @@ -31,6 +31,7 @@ int parse_mem_string(char *str, uint64_t *val);
>  
>  void enable_trace_mark(void);
>  void tracemark(char *fmt, ...) __attribute__((format(printf, 1, 2)));
> +void tracing_stop(void);
>  void disable_trace_mark(void);
>  
>  #define MSEC_PER_SEC		1000
> diff --git a/src/lib/rt-utils.c b/src/lib/rt-utils.c
> index 294fc9683a122..e504b17738411 100644
> --- a/src/lib/rt-utils.c
> +++ b/src/lib/rt-utils.c
> @@ -427,7 +427,7 @@ void tracemark(char *fmt, ...)
>  
>  	/* bail out if we're not tracing */
>  	/* or if the kernel doesn't support trace_mark */
> -	if (tracemark_fd < 0 || trace_fd < 0)
> +	if (tracemark_fd < 0)
>  		return;
>  
>  	va_start(ap, fmt);
> @@ -436,8 +436,12 @@ void tracemark(char *fmt, ...)
>  
>  	/* write the tracemark message */
>  	write(tracemark_fd, tracebuf, len);
> +}
>  
> -	/* now stop any trace */
> +void tracing_stop(void)
> +{
> +	if (trace_fd < 0)
> +		return;
>  	write(trace_fd, "0\n", 2);
>  }
>  
> diff --git a/src/oslat/oslat.c b/src/oslat/oslat.c
> index 9e5a08a2fbd92..4291221dc6521 100644
> --- a/src/oslat/oslat.c
> +++ b/src/oslat/oslat.c
> @@ -340,6 +340,7 @@ static void insert_bucket(struct thread *t, stamp_t value)
>  		char *line = "%s: Trace threshold (%d us) triggered on cpu %d with %.*f us!\n";
>  		tracemark(line, g.app_name, g.trace_threshold, t->core_i,
>  			  g.precision, us);
> +		tracing_stop();
>  		err_quit(line, g.app_name, g.trace_threshold, t->core_i,
>  			 g.precision, us);
>  	}
> diff --git a/src/sched_deadline/cyclicdeadline.c b/src/sched_deadline/cyclicdeadline.c
> index 04e61edc68d83..e2f827deb275a 100644
> --- a/src/sched_deadline/cyclicdeadline.c
> +++ b/src/sched_deadline/cyclicdeadline.c
> @@ -885,6 +885,7 @@ void *run_deadline(void *data)
>  				break_thread_value = stat->max;
>  				tracemark("hit latency threshold (%lld > %d)",
>  						 (unsigned long long) stat->max, tracelimit);
> +				tracing_stop();
>  			}
>  			pthread_mutex_unlock(&break_thread_id_lock);
>  			break;
> -- 
> 2.51.0
> 
> 
    - Fixed spelling of "writing" and "afterwards"
    Signed-off-by: John Kacur <jkacur@redhat.com>