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

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Message-ID: <20190904082046.GB2349@hirez.programming.kicks-ass.net>
Date:   Wed, 4 Sep 2019 10:20:46 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Viktor Rosendahl <viktor.rosendahl@...il.com>
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        Joel Fernandes <joel@...lfernandes.org>
Subject: Re: [PATCH v5 1/4] ftrace: Implement fs notification for
 tracing_max_latency

On Tue, Sep 03, 2019 at 03:25:59PM +0200, Viktor Rosendahl wrote:

> It seems like it would be possible to simply replace the calls to
> latency_fsnotify_enable/disable() with calls to
> start/stop_critical_timings(). However, the main problem is that it
> would not work for the wakup tracer. The wakeup tracer needs a
> facility that postpones the notifications, not one that prevents the
> measurements because all its measurements takes place in the middle
> of __schedule(). On the other hand, in some places, like in idle and
> the console we need start stop functions that prevents the
> measurements from being make.

Like Joel already mentioned; you can use irq_work here.