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Date:   Wed, 29 May 2019 10:29:45 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Daniel Bristot de Oliveira <bristot@redhat.com>
Cc:     linux-kernel@vger.kernel.org, williams@redhat.com,
        daniel@bristot.me, "Steven Rostedt (VMware)" <rostedt@goodmis.org>,
        Ingo Molnar <mingo@redhat.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        Matthias Kaehlcke <mka@chromium.org>,
        "Joel Fernandes (Google)" <joel@joelfernandes.org>,
        Frederic Weisbecker <frederic@kernel.org>,
        Yangtao Li <tiny.windzz@gmail.com>,
        Tommaso Cucinotta <tommaso.cucinotta@santannapisa.it>
Subject: Re: [RFC 1/3] softirq: Use preempt_latency_stop/start to trace
 preemption
Message-ID: <20190529082945.GE2623@hirez.programming.kicks-ass.net>
References: <cover.1559051152.git.bristot@redhat.com>
 <b6bb4705efb0c01c11008ae3c46bc74555245303.1559051152.git.bristot@redhat.com>
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On Tue, May 28, 2019 at 05:16:22PM +0200, Daniel Bristot de Oliveira wrote:
> prempt_disable/enable tracepoints occurs only in the preemption
> enabled <-> disable transition. As preempt_latency_stop() and
> preempt_latency_start() already do this control, avoid code
> duplication by using these functions in the softirq code as well.
> 
> RFC: Should we move preempt_latency_start/preempt_latency_stop
> to a trace source file... or even a header?

Yeah, a header might not be a bad idea.

> @@ -130,12 +132,8 @@ void __local_bh_disable_ip(unsigned long ip, unsigned int cnt)
>  		trace_softirqs_off(ip);
>  	raw_local_irq_restore(flags);
>  
> -	if (preempt_count() == cnt) {
> -#ifdef CONFIG_DEBUG_PREEMPT
> -		current->preempt_disable_ip = get_lock_parent_ip();
> -#endif
> -		trace_preempt_off(CALLER_ADDR0, get_lock_parent_ip());
> -	}
> +	preempt_latency_start(cnt);
> +

I'm thinking we can do without that empty line.

>  }
>  EXPORT_SYMBOL(__local_bh_disable_ip);
>  #endif /* CONFIG_TRACE_IRQFLAGS */