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From: Herbert Xu <herbert@gondor.apana.org.au>
To: David Miller <davem@davemloft.net>
Cc: eric.dumazet@gmail.com, phil@nwl.cc, netdev@vger.kernel.org,
	linux-kernel@vger.kernel.org, tgraf@suug.ch,
	fengguang.wu@intel.com, wfg@linux.intel.com, lkp@01.org
Subject: Re: rhashtable: Use __vmalloc with GFP_ATOMIC for table allocation
Date: Sat, 5 Dec 2015 15:03:54 +0800	[thread overview]
Message-ID: <20151205070354.GA23255@gondor.apana.org.au> (raw)
In-Reply-To: <20151204.165334.1119277452308794437.davem@davemloft.net>

On Fri, Dec 04, 2015 at 04:53:34PM -0500, David Miller wrote:
> From: Herbert Xu <herbert@gondor.apana.org.au>
> Date: Fri, 4 Dec 2015 22:39:56 +0800
> 
> > When an rhashtable user pounds rhashtable hard with back-to-back
> > insertions we may end up growing the table in GFP_ATOMIC context.
> > Unfortunately when the table reaches a certain size this often
> > fails because we don't have enough physically contiguous pages
> > to hold the new table.
> > 
> > Eric Dumazet suggested (and in fact wrote this patch) using
> > __vmalloc instead which can be used in GFP_ATOMIC context.
> > 
> > Reported-by: Phil Sutter <phil@nwl.cc>
> > Suggested-by: Eric Dumazet <eric.dumazet@gmail.com>
> > Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
> 
> Applied, thanks Herbert.

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.

Thanks,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

  reply	other threads:[~2015-12-05  7:04 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-11-20 17:17 [PATCH v2 0/4] improve fault-tolerance of rhashtable runtime-test Phil Sutter
2015-11-20 17:17 ` [PATCH v2 1/4] rhashtable-test: add cond_resched() to thread test Phil Sutter
2015-11-20 17:17 ` [PATCH v2 2/4] rhashtable-test: retry insert operations Phil Sutter
2015-11-20 17:17 ` [PATCH v2 3/4] rhashtable-test: calculate max_entries value by default Phil Sutter
2015-11-20 17:17 ` [PATCH v2 4/4] rhashtable-test: allow to retry even if -ENOMEM was returned Phil Sutter
2015-11-20 17:28   ` Phil Sutter
2015-11-23 17:38 ` [PATCH v2 0/4] improve fault-tolerance of rhashtable runtime-test David Miller
2015-11-30  9:37 ` Herbert Xu
2015-11-30 10:14   ` Phil Sutter
2015-11-30 10:18     ` Herbert Xu
2015-12-03 12:41       ` rhashtable: Prevent spurious EBUSY errors on insertion Herbert Xu
2015-12-03 15:38         ` Phil Sutter
2015-12-04 19:38         ` David Miller
2015-12-17  8:46         ` Xin Long
2015-12-17  8:48           ` Herbert Xu
2015-12-17  9:00             ` Xin Long
2015-12-17 16:07               ` Xin Long
2015-12-18  2:26                 ` Herbert Xu
2015-12-18  8:18                   ` Xin Long
2015-12-17 17:00               ` David Miller
2015-12-03 12:51       ` rhashtable: ENOMEM errors when hit with a flood of insertions Herbert Xu
2015-12-03 15:08         ` David Laight
2015-12-03 16:08         ` Eric Dumazet
2015-12-04  0:07           ` Herbert Xu
2015-12-04 14:39           ` rhashtable: Use __vmalloc with GFP_ATOMIC for table allocation Herbert Xu
2015-12-04 17:01             ` Phil Sutter
2015-12-04 17:45               ` Eric Dumazet
2015-12-04 18:15                 ` Phil Sutter
2015-12-05  7:06                   ` Herbert Xu
2015-12-07 15:35                     ` Thomas Graf
2015-12-07 19:29                       ` David Miller
2015-12-09  2:18                     ` Thomas Graf
2015-12-09  2:24                       ` Herbert Xu
2015-12-09  2:36                         ` Thomas Graf
2015-12-09  2:38                           ` Herbert Xu
2015-12-09  2:42                             ` Thomas Graf
2015-12-04 21:53             ` David Miller
2015-12-05  7:03               ` Herbert Xu [this message]
2015-12-06  3:48                 ` David Miller

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