linux-kernel - Re: zram: zsmalloc calls sleeping function from atomic context

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Date:	Tue, 18 Mar 2014 13:52:45 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
	Minchan Kim <minchan@...nel.org>,
	Nitin Gupta <ngupta@...are.org>,
	Jerome Marchand <jmarchan@...hat.com>,
	linux-kernel@...r.kernel.org,
	David Vrabel <david.vrabel@...rix.com>,
	Dietmar Hahn <dietmar.hahn@...fujitsu.com>
Subject: Re: zram: zsmalloc calls sleeping function from atomic context

On Mon, Mar 17, 2014 at 04:01:17PM -0700, Andrew Morton wrote:
> btw, I note that vunmap() itself already has a might_sleep() in it, and
> I can't work out why - I don't think it _does_ sleep.  The changelog to
> 34754b69a6f87aa6aa is, in toto:
> 
> "x86: make vmap yell louder when it is used under irqs_disabled()"
> 
> No explanation *why*.  And why didn't it use WARN_ON(irqs_disabled())?

Man I suck.. and 5 years ago too. I can barely remember last week.

Lets see if the email archive has clues.

vmap()
  get_vm_area_caller()
    __get_vm_area_node(.gfp = GFP_KERNEL)
      kmalloc_node(gfp);


It does sleep.

https://lkml.org/lkml/2009/2/13/115
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