linux-kernel - Re: [PATCH 3/4] tracing: Add stack_tracer

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Message-ID: <20170406172348.6df0201b@gandalf.local.home>
Date:   Thu, 6 Apr 2017 17:23:48 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:     linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 3/4] tracing: Add stack_tracer_disable/enable()
 functions

On Thu, 6 Apr 2017 13:21:17 -0700
"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> wrote:

> > My worry is that we add another caller that doesn't disable interrupts
> > or preemption.
> > 
> > I could add a __stack_trace_disable() that skips the disabling of
> > preemption, as the "__" usually denotes the call is "special".  
> 
> Given that interrupts are disabled at that point, and given also that
> NMI skips stack tracing if growth is required, could we just leave
> out the stack_tracer_disable() and stack_tracer_enable()?

There may be other use cases. Hmm, maybe I'll just have it do a check
to make sure preemption is disabled. Something like:

	if (IS_ENABLED(CONFIG_DEBUG_PREEMPT))
		WARN_ON_ONCE(!preempt_count());

-- Steve