linux-kernel - Re: [PATCH] perf, x86: Fall back to vmalloc for BTS buffer allocation

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Message-ID: <20140910163556.GE4783@worktop.ger.corp.intel.com>
Date:	Wed, 10 Sep 2014 18:35:56 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	linux-kernel@...r.kernel.org, mingo@...nel.org, eranian@...gle.com,
	tglx@...utronix.de, Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH] perf, x86: Fall back to vmalloc for BTS buffer allocation

On Wed, Sep 10, 2014 at 04:40:12PM +0200, Andi Kleen wrote:
> > We did this once, and that blew up big time.
> > 
> > Even now, vmalloc_fault() has a very explicit:
> > 
> >   WARN_ON_ONCE(in_nmi());
> > 
> > So this isn't going to happen until you fix that.
> 
> Good point.
> 
> We just need to call vmalloc_sync_all at allocation time,
> no need to change vmalloc_fault.

Somehow that wasn't considered adequate, but lemme try and dig out that
thread. It should be somewhere...

https://lkml.org/lkml/2010/7/14/465


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