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Subject: Re: percpu related boot crash on x86
From: Eric Dumazet <eric.dumazet@gmail.com>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Pekka Enberg <penberg@kernel.org>, Ingo Molnar <mingo@elte.hu>,
        Tejun Heo <tj@kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>, "H. Peter Anvin" <hpa@zytor.com>,
        Andrew Morton <akpm@linux-foundation.org>
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Date: Thu, 20 Jan 2011 12:12:47 +0100
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Le jeudi 20 janvier 2011 à 11:47 +0100, Peter Zijlstra a écrit :
> On Thu, 2011-01-20 at 10:31 +0200, Pekka Enberg wrote:
> >    if (!irqs_disabled())
> > 
> > guard around the debugging code to make vfree() always work with IRQs 
> > disabled. 
> 
> That won't be sufficient, __purge_vmap_area_lazy() needs to call
> flush_tlb_kernel_range() occasionally.
> 
> There really is a good reason vmalloc()/vfree() don't work with
> interrupts disabled.
> 

Hmm, I would try to increase PERCPU_DYNAMIC_RESERVE, or pcpu_mem_alloc()
could try to use kzalloc() even for allocations bigger than one PAGE,
and fallback to vzalloc().

We have more alloc_percpu() uses, we also should try to use first chunk
if possible.