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From: Steven Rostedt <rostedt@goodmis.org>
To: Nam Cao <namcao@linutronix.de>
Cc: Masami Hiramatsu <mhiramat@kernel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	linux-trace-kernel@vger.kernel.org, linux-kernel@vger.kernel.org,
	Gabriele Monaco <gmonaco@redhat.com>,
	john.ogness@linutronix.de
Subject: Re: [PATCH] tracing: Remove pointless memory barriers
Date: Mon, 21 Jul 2025 20:49:32 -0400	[thread overview]
Message-ID: <20250721204932.306da76c@gandalf.local.home> (raw)
In-Reply-To: <20250626160459.soHxOROG@linutronix.de>

On Thu, 26 Jun 2025 18:04:59 +0200
Nam Cao <namcao@linutronix.de> wrote:

> > The above three interact with each other. Without the barriers, the
> > tr->buffer_disabled = 0, can be set on one CPU, and the other CPU can think
> > the buffer is still enabled and do work that will end up doing nothing. Or
> > it can be set to 1, and the other CPU still sees it disabled and will not
> > do work when it can.  
> 
> (I'm not that experienced with memory barrier, so I may be writing nonsense
> here)

So I did some git archeology and realized that the buffer_disabled is just
a cache to make irqsoff tracing faster. The commit even said it's not going
to be accurate.

OK, I'll just take this patch.

Thanks,

-- Steve

      parent reply	other threads:[~2025-07-22  0:49 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-06-26 15:19 [PATCH] tracing: Remove pointless memory barriers Nam Cao
2025-06-26 15:35 ` Steven Rostedt
2025-06-26 15:37   ` Steven Rostedt
2025-06-26 16:04   ` Nam Cao
2025-06-26 16:34     ` Steven Rostedt
2025-06-26 17:41       ` John Ogness
2025-07-03  8:05         ` Gabriele Monaco
2025-07-08  7:42           ` Nam Cao
2025-07-09 15:08             ` Steven Rostedt
2025-07-11  8:29               ` David Laight
2025-07-11 16:07                 ` Steven Rostedt
2025-07-09  8:22       ` David Laight
2025-07-22  0:49     ` Steven Rostedt [this message]

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