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Date: Tue, 10 Mar 2026 15:12:45 +0000
From: Dmitry Ilvokhin <d@ilvokhin.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Dennis Zhou <dennis@kernel.org>, Tejun Heo <tj@kernel.org>,
	Christoph Lameter <cl@gentwo.org>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>, Will Deacon <will@kernel.org>,
	Boqun Feng <boqun@kernel.org>, Waiman Long <longman@redhat.com>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	linux-trace-kernel@vger.kernel.org, kernel-team@meta.com
Subject: Re: [PATCH RFC 3/3] locking: Wire up contended_release tracepoint
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In-Reply-To: <20260305105924.7069eb23@gandalf.local.home>

On Thu, Mar 05, 2026 at 10:59:24AM -0500, Steven Rostedt wrote:
> On Wed,  4 Mar 2026 16:56:17 +0000
> Dmitry Ilvokhin <d@ilvokhin.com> wrote:
> 
> > @@ -204,6 +206,8 @@ static inline void rwbase_write_unlock(struct rwbase_rt *rwb)
> >  	unsigned long flags;
> >  
> >  	raw_spin_lock_irqsave(&rtm->wait_lock, flags);
> > +	if (rt_mutex_has_waiters(rtm))
> > +		trace_contended_release(rwb);
> 
> Hmm, if statements should never be used just for tracepoints without a
> static branch. The above should be:
> 
> 	if (trace_contended_release_enabled() && rt_mutex_has_waiters(rtm))
> 		trace_contended_release(rwb);
> 
> The above "trace_contened_release_enabled()" is a static_branch where it
> turns the if statement into a nop when the tracepoint is not enabled, and a
> jmp when it is.

Thanks for catching this, Steven. Fixed locally.