Re: [PATCH v4] lockdep: check that no locks held at freeze time

From: Andrew Morton
Date: Wed Feb 20 2013 - 19:43:20 EST

On Wed, 20 Feb 2013 16:28:07 -0800
Mandeep Singh Baines <msb@xxxxxxxxxxxx> wrote:

> > Backtraces aren't *that* bad. We'll easily be able to tell which of
> > the two callsites triggered the trace.
> >
> Let's say there was a try_to_freeze() that got inlined indirectly
> (multiple levels of inline) into do_exit. Wouldn't the backtraces for
> the regular exit check and the try_to_freeze check be identical except
> for the offset (do_exit+0x45 versus do_exit+0x88)? So unless you had
> an object file you wouldn't know which check you hit.

Mutter. Spose so. Vaguely possible. Yes, if we want to avoid a
wont-happen, use __FILE__ and __LINE__. Or, probably more sanely,

Or uninline try_to_freeze(). If anything's calling that at high
frequency, we have a problem. And given the number of callsites,
getting it into icache might result in a faster kernel...

(Someone needs to teach __might_sleep() about __ratelimit())
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