Re: [PATCH 1/2] break out page allocation warning code

From: David Rientjes
Date: Tue Apr 19 2011 - 17:23:49 EST


On Mon, 18 Apr 2011, Dave Hansen wrote:

> > It shouldn't be a follow-on patch since you're introducing a new feature
> > here (vmalloc allocation failure warnings) and what I'm identifying is a
> > race in the access to current->comm. A bug fix for a race should always
> > preceed a feature that touches the same code.
>
> Dude. Seriously. Glass house! a63d83f4
>

Not sure what you're implying here. The commit you've identified is the
oom killer rewrite and the oom killer is very specific about making sure
to always hold task_lock() whenever dereferencing ->comm, even for
current, to guard against /proc/pid/comm or prctl(). The oom killer is
different from your usecase, however, because we can always take
task_lock(current) in the oom killer because it's in a blockable context,
whereas page allocation warnings can occur in a superset.
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