linux-kernel - Re: [PATCH v5 1/4] ftrace: Implement fs notification for tracing_max

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20190904073915.4a145a91@oasis.local.home>
Date:   Wed, 4 Sep 2019 07:39:15 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Viktor Rosendahl <viktor.rosendahl@...il.com>
Cc:     Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        Joel Fernandes <joel@...lfernandes.org>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v5 1/4] ftrace: Implement fs notification for
 tracing_max_latency

On Tue,  3 Sep 2019 15:25:59 +0200
Viktor Rosendahl <viktor.rosendahl@...il.com> wrote:

> +void latency_fsnotify_stop(void)
> +{
> +	/* Make sure all CPUs see caller's previous actions to stop tracer */
> +	smp_wmb();

These memory barriers just look wrong. What exactly are you trying to protect here?

Where's the matching rmbs?

-- Steve

> +	static_branch_disable(&latency_notify_key);
> +	latency_fsnotify_process();
> +}
> +
> +void latency_fsnotify_start(void)
> +{
> +	static_branch_enable(&latency_notify_key);
> +	/* Make sure all CPUs see key value before caller continue */
> +	smp_wmb();
> +}
> +