From: Peter Zijlstra <peterz@infradead.org>
To: frank.rowand@am.sony.com
Cc: "tglx@linutronix.de" <tglx@linutronix.de>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] PREEMPT_RT_FULL: arm coredump fails for cpu >= 4
Date: Wed, 28 Sep 2011 15:03:13 +0200 [thread overview]
Message-ID: <1317214993.24040.16.camel@twins> (raw)
In-Reply-To: <4E828E35.6070801@am.sony.com>
On Tue, 2011-09-27 at 20:02 -0700, Frank Rowand wrote:
>
> ARM can not use SPLIT_PTLOCK_CPUS if PREEMPT_RT_FULL because
> vectors_user_mapping() creates a VM_ALWAYSDUMP mapping of the vector page,
> but no ptl->lock has been allocated for the page. An attempt to coredump
> that page will result in a kernel NULL pointer dereference when
> follow_page() attempts to lock the page.
>
> This patch is needed only if mm-shrink-the-page-frame-to-rt-size.patch is
> applied.
Yeah, vile hackery that is.. why isn't pgtable_page_ctor() called on
those pages?
Not that I care too much about split_pte_lock on ARM, they're mostly all
tiny machines anyway so the gain is marginal, but it would be good to
find out why the pgtable constructor isn't called properly.
next prev parent reply other threads:[~2011-09-28 13:03 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-28 3:02 [PATCH] PREEMPT_RT_FULL: arm coredump fails for cpu >= 4 Frank Rowand
2011-09-28 13:03 ` Peter Zijlstra [this message]
2011-09-28 18:33 ` Frank Rowand
2011-10-02 1:58 ` Frank Rowand
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