linux-kernel - Re: [PATCH 05/48] percpu: Add preemption checks to __this

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Message-ID: <alpine.DEB.2.10.1403042125060.3742@nuc>
Date:	Tue, 4 Mar 2014 21:27:14 -0600 (CST)
From:	Christoph Lameter <cl@...ux.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
cc:	Tejun Heo <tj@...nel.org>, akpm@...uxfoundation.org,
	rostedt@...dmis.org, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 05/48] percpu: Add preemption checks to __this_cpu ops

On Tue, 4 Mar 2014, Andrew Morton wrote:

> >  	print_symbol("caller is %s\n", (long)__builtin_return_address(0));
> >  	dump_stack();
>
> I wonder if there's any point in printing __builtin_return_address.
> Doesn't dump_stack() tell us the same thing?

Yes it does. However, it was there before and software may scan the logs
for it.

> > +notrace void __this_cpu_preempt_check(const char *op)
> > +{
> > +	char text[40];
> > +
> > +	snprintf(text, sizeof(text), "__this_cpu_%s()", op);
> > +	check_preemption_disabled(text);
> > +}
>
> I'd like to see a comment here telling scared readers why this can
> never overflow text[].

Ok. I can also add VM_BUG_ON(strlen(op) >= sizeof(text)) ?

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