linux-kernel - Re: rhashtable: Use __vmalloc with GFP

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Message-Id: <20151205.224829.171477269244585844.davem@davemloft.net>
Date:	Sat, 05 Dec 2015 22:48:29 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	herbert@...dor.apana.org.au
Cc:	eric.dumazet@...il.com, phil@....cc, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, tgraf@...g.ch,
	fengguang.wu@...el.com, wfg@...ux.intel.com, lkp@...org
Subject: Re: rhashtable: Use __vmalloc with GFP_ATOMIC for table allocation

From: Herbert Xu <herbert@...dor.apana.org.au>
Date: Sat, 5 Dec 2015 15:03:54 +0800

> Sorry Dave but you'll have to revert this because I've been able
> to trigger the following crash with the patch:
> 
> Testing concurrent rhashtable access from 50 threads
> ------------[ cut here ]------------
> kernel BUG at ../mm/vmalloc.c:1337!
> invalid opcode: 0000 [#1] PREEMPT SMP 
> 
> The reason is that because I was testing insertions with BH disabled,
> and __vmalloc doesn't like that, even with GFP_ATOMIC.  As we
> obviously want to continue to support rhashtable users inserting
> entries with BH disabled, we'll have to look for an alternate
> solution.

Ok, reverted, thanks for the heads up.
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