linux-kernel - Re: [PATCH v1 2/2] cleanup.h: Introduce DEFINE_INACTIVE_GUARD and activate

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Message-ID: <20240902154334.GH4723@noisy.programming.kicks-ass.net>
Date: Mon, 2 Sep 2024 17:43:34 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc: Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Kees Cook <keescook@...omium.org>,
	Greg KH <gregkh@...uxfoundation.org>,
	Sean Christopherson <seanjc@...gle.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Alexei Starovoitov <ast@...nel.org>, Yonghong Song <yhs@...com>,
	"Paul E . McKenney" <paulmck@...nel.org>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Namhyung Kim <namhyung@...nel.org>, bpf@...r.kernel.org,
	Joel Fernandes <joel@...lfernandes.org>,
	linux-trace-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH v1 2/2] cleanup.h: Introduce DEFINE_INACTIVE_GUARD and
 activate_guard

On Wed, Aug 28, 2024 at 10:37:19AM -0400, Mathieu Desnoyers wrote:
> To cover scenarios where the scope of the guard differs from the scope
> of its activation, introduce DEFINE_INACTIVE_GUARD() and activate_guard().
> 
> Here is an example use for a conditionally activated guard variable:
> 
> void func(bool a)
> {
> 	DEFINE_INACTIVE_GUARD(preempt_notrace, myguard);
> 
> 	[...]
> 	if (a) {
> 		might_sleep();
> 		activate_guard(preempt_notrace, myguard)();
> 	}
> 	[ protected code ]
> }

So... I more or less proposed this much earlier:

  https://lore.kernel.org/all/20230919131038.GC39346@noisy.programming.kicks-ass.net/T/#mb7b84212619ac743dfe4d2cc81decce451586b27

and Linus took objection to similar patterns. But perhaps my naming
wasn't right.