linux-kernel - Re: [PATCH v2 15/18] rtla: Make stop

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Message-ID: <d40f598776e7995c9f1559514e89ccff51d91f9c.camel@redhat.com>
Date: Tue, 06 Jan 2026 11:47:56 -0600
From: Crystal Wood <crwood@...hat.com>
To: Steven Rostedt <rostedt@...dmis.org>, Wander Lairson Costa
	 <wander@...hat.com>
Cc: Tomas Glozar <tglozar@...hat.com>, Ivan Pravdin	
 <ipravdin.official@...il.com>, Costa Shulyupin <costa.shul@...hat.com>,
 John Kacur <jkacur@...hat.com>, Tiezhu Yang <yangtiezhu@...ngson.cn>, "open
 list:Real-time Linux Analysis (RTLA) tools"
 <linux-trace-kernel@...r.kernel.org>, "open list:Real-time Linux Analysis
 (RTLA) tools"	 <linux-kernel@...r.kernel.org>, "open list:BPF
 [MISC]:Keyword:(?:\\b|_)bpf(?:\\b|_)"	 <bpf@...r.kernel.org>
Subject: Re: [PATCH v2 15/18] rtla: Make stop_tracing variable volatile

On Tue, 2026-01-06 at 11:05 -0500, Steven Rostedt wrote:
> On Tue,  6 Jan 2026 08:49:51 -0300
> Wander Lairson Costa <wander@...hat.com> wrote:
> 
> > Add the volatile qualifier to stop_tracing in both common.c and
> > common.h to ensure all accesses to this variable bypass compiler
> > optimizations and read directly from memory. This guarantees that
> > when the signal handler sets stop_tracing, the change is immediately
> > visible to the main program loop, preventing potential hangs or
> > delayed shutdown when termination signals are received.
> 
> In the kernel, this is handled via the READ_ONCE() macro. Perhaps rtla
> should implement that too.

Or just get it from tools/include/linux/compiler.h.  No need to reinvent
the wheel (even though several other tools do).

That said, signal safety is a pretty routine use for volatile.

-Crystal