From: Daniel Borkmann <daniel@iogearbox.net>
To: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Jiri Pirko <jiri@resnulli.us>, Cong Wang <cwang@twopensource.com>,
David Miller <davem@davemloft.net>,
Nicolas Dichtel <nicolas.dichtel@6wind.com>,
Thomas Graf <tgraf@suug.ch>, Scott Feldman <sfeldma@gmail.com>,
Network Development <netdev@vger.kernel.org>
Subject: Re: rtnl_mutex deadlock?
Date: Fri, 07 Aug 2015 01:58:15 +0200 [thread overview]
Message-ID: <55C3F497.6020003@iogearbox.net> (raw)
In-Reply-To: <20150806234117.GA22588@gondor.apana.org.au>
On 08/07/2015 01:41 AM, Herbert Xu wrote:
> On Thu, Aug 06, 2015 at 04:50:39PM +0200, Daniel Borkmann wrote:
>>
>> Then, in __rhashtable_insert_fast(), I could trigger an -EBUSY when I'm
>> really unlucky and exceed the ht->elasticity limit of 16. I would then
>> end up in rhashtable_insert_rehash() to find out there's already one
>> ongoing and thus, I'm getting -EBUSY via __netlink_insert().
>
> Right, so the only way you can trigger this is if you hit a chain
> longer than 16 and the number of entries in the table is less than
> 75% the size of the table, as well as there being an existing resize
> or rehash operation.
>
> This should be pretty much impossible.
>
> But if we had a WARN_ON_ONCE there then we'll know for sure.
Looks like we had a WARN_ON() in rhashtable_insert_rehash() before, but
was removed in a87b9ebf1709 ("rhashtable: Do not schedule more than one
rehash if we can't grow further"). Do you want to re-add a WARN_ON_ONCE()?
Thanks,
Daniel
next prev parent reply other threads:[~2015-08-06 23:58 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-08-04 15:48 rtnl_mutex deadlock? Linus Torvalds
2015-08-05 5:31 ` Cong Wang
2015-08-05 7:43 ` Jiri Pirko
2015-08-05 8:44 ` Linus Torvalds
2015-08-05 18:59 ` Daniel Borkmann
2015-08-06 0:30 ` Herbert Xu
2015-08-06 14:50 ` Daniel Borkmann
2015-08-06 22:39 ` Daniel Borkmann
2015-08-06 23:42 ` Herbert Xu
2015-08-06 23:41 ` Herbert Xu
2015-08-06 23:58 ` Daniel Borkmann [this message]
2015-08-07 0:00 ` Herbert Xu
2015-08-08 17:22 ` Thomas Graf
2015-08-06 5:19 ` Herbert Xu
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=55C3F497.6020003@iogearbox.net \
--to=daniel@iogearbox.net \
--cc=cwang@twopensource.com \
--cc=davem@davemloft.net \
--cc=herbert@gondor.apana.org.au \
--cc=jiri@resnulli.us \
--cc=netdev@vger.kernel.org \
--cc=nicolas.dichtel@6wind.com \
--cc=sfeldma@gmail.com \
--cc=tgraf@suug.ch \
--cc=torvalds@linux-foundation.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).