linux-kernel - Re: [PATCH 1/5] tracing/ftrace: Types and naming corrections for sched tracer

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Date:	Wed, 22 Oct 2008 19:35:54 +0200
From:	"Frédéric Weisbecker" <fweisbec@...il.com>
To:	"Ingo Molnar" <mingo@...e.hu>,
	"Steven Rostedt" <rostedt@...dmis.org>,
	"Linux Kernel" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/5] tracing/ftrace: Types and naming corrections for sched tracer

2008/10/22 Frederic Weisbecker <fweisbec@...il.com>:
> This patch applies some corrections suggested by Steven Rostedt.
>
> Change the type of shed_ref into int since it is used
> into a Mutex, we don't need it anymore as an atomic
> variable in the sched_switch tracer.
> Also change the name of the register mutex.
>
>
> Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
> Cc: Steven Rostedt <rostedt@...dmis.org>
> ---
>  kernel/trace/trace_sched_switch.c |   30 +++++++++++++-----------------
>  1 files changed, 13 insertions(+), 17 deletions(-)
>
> diff --git a/kernel/trace/trace_sched_switch.c
> b/kernel/trace/trace_sched_switch.c
> index 9d7bdac..969953b 100644
> --- a/kernel/trace/trace_sched_switch.c
> +++ b/kernel/trace/trace_sched_switch.c
> @@ -16,8 +16,8 @@
>
>  static struct trace_array      *ctx_trace;
>  static int __read_mostly       tracer_enabled;
> -static atomic_t                sched_ref;
> -static DEFINE_MUTEX(tracepoint_mutex);
> +static int                     sched_ref;
> +static DEFINE_MUTEX(sched_register_mutex);
>
>  static void
>  probe_sched_switch(struct rq *__rq, struct task_struct *prev,
> @@ -28,7 +28,7 @@ probe_sched_switch(struct rq *__rq, struct task_struct *prev,
>        int cpu;
>        int pc;
>
> -       if (!atomic_read(&sched_ref))
> +       if (!sched_ref)
>                return;
>
>        tracing_record_cmdline(prev);
> @@ -124,26 +124,22 @@ static void tracing_sched_unregister(void)
>
>  static void tracing_start_sched_switch(void)
>  {
> -       long ref;
> -
> -       mutex_lock(&tracepoint_mutex);
> -        tracer_enabled = 1;
> -       ref = atomic_inc_return(&sched_ref);
> -       if (ref == 1)
> +       mutex_lock(&sched_register_mutex);
> +       if (!(sched_ref++)) {
> +               tracer_enabled = 1;
>                tracing_sched_register();
> -       mutex_unlock(&tracepoint_mutex);
> +       }
> +       mutex_unlock(&sched_register_mutex);
>  }
>
>  static void tracing_stop_sched_switch(void)
>  {
> -       long ref;
> -
> -       mutex_lock(&tracepoint_mutex);
> -       tracer_enabled = 0;
> -       ref = atomic_dec_and_test(&sched_ref);
> -       if (ref)
> +       mutex_lock(&sched_register_mutex);
> +       if (!(--sched_ref)) {
>                tracing_sched_unregister();
> -       mutex_unlock(&tracepoint_mutex);
> +               tracer_enabled = 0;
> +       }
> +       mutex_unlock(&sched_register_mutex);
>  }
>
>  void tracing_start_cmdline_record(void)
>

Correction, it's not anymore a 1/5, it's just a resend.
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