netdev - Re: rhashtable: Use __vmalloc with GFP

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Date:	Mon, 7 Dec 2015 16:35:24 +0100
From:	Thomas Graf <tgraf@...g.ch>
To:	Herbert Xu <herbert@...dor.apana.org.au>
Cc:	Phil Sutter <phil@....cc>, Eric Dumazet <eric.dumazet@...il.com>,
	davem@...emloft.net, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, fengguang.wu@...el.com,
	wfg@...ux.intel.com, lkp@...org
Subject: Re: rhashtable: Use __vmalloc with GFP_ATOMIC for table allocation

On 12/05/15 at 03:06pm, Herbert Xu wrote:
> On Fri, Dec 04, 2015 at 07:15:55PM +0100, Phil Sutter wrote:
> >
> > > Only one should really do this, while others are waiting.
> > 
> > Sure, that was my previous understanding of how this thing works.
> 
> Yes that's clearly how it should be.  Unfortunately while adding
> the locking to do this, I found out that you can't actually call
> __vmalloc with BH disabled so this is a no-go.
> 
> Unless we can make __vmalloc work with BH disabled, I guess we'll
> have to go back to multi-level lookups unless someone has a better
> suggestion.

Thanks for fixing the race.

As for the remaining problem, I think we'll have to find a way to
serve a hard pounding user if we want to convert TCP hashtables
later on.

Did you look into what __vmalloc prevents to work with BH disabled?
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