linux-kernel - Re: rhashtable: Prevent spurious EBUSY errors on insertion

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Date:	Thu, 17 Dec 2015 12:00:24 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	lucien.xin@...il.com
Cc:	herbert@...dor.apana.org.au, 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: Prevent spurious EBUSY errors on insertion

From: Xin Long <lucien.xin@...il.com>
Date: Thu, 17 Dec 2015 17:00:35 +0800

> On Thu, Dec 17, 2015 at 4:48 PM, Herbert Xu <herbert@...dor.apana.org.au> wrote:
>> On Thu, Dec 17, 2015 at 04:46:00PM +0800, Xin Long wrote:
>>>
>>> sorry for late test, but unfortunately, my case with rhashtalbe still
>>> return EBUSY.
>>> I added some debug code in rhashtable_insert_rehash(), and found:
>>> *future_tbl is null*
>>>
>>> fail:
>>>         /* Do not fail the insert if someone else did a rehash. */
>>>         if (likely(rcu_dereference_raw(tbl->future_tbl))) {
>>>                 printk("future_tbl is there\n");
>>>                 return 0;
>>>         } else {
>>>                 printk("future_tbl is null\n");
>>>         }
>>>
>>> any idea why ?
>>
>> That's presumably because you got a genuine double rehash.
>>
>> Until you post your code we can't really help you.
>>
> i wish i could , but my codes is a big patch for sctp, and this issue
> happens in a special stress test based on this patch.
> im trying to think how i can show you. :)

Simply post it.
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