linux-ext4 - Re: Help on Implementation of EXT3 type Ordered Mode in EXT4

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20100329154534.GE5835@quack.suse.cz>
Date:	Mon, 29 Mar 2010 17:45:34 +0200
From:	Jan Kara <jack@...e.cz>
To:	Kailas Joshi <kailas.joshi@...il.com>
Cc:	tytso@....edu, linux-ext4@...r.kernel.org,
	Jiaying Zhang <jiayingz@...gle.com>
Subject: Re: Help on Implementation of EXT3 type Ordered Mode in EXT4

  Hi,

On Tue 23-03-10 16:11:45, Kailas Joshi wrote:
> I have Lock Debugging enables but that didn't give any warnings.
> However, when I did echo "w" >/proc/sysrq-trigger after system lockup,
> I got the stack trace for locked up process.
> 
> Following are the stack traces of the processes (I suspect) resulting
> in total system lockup -
  <snip>

  So kjournald is waiting on a page lock and everyone else waits for
kjournald to finish committing or for page lock as well. The strange thing
is that I don't see anybody who could hold the page lock everyone is
waiting on. So I think further debugging should go in this direction - find
out on which page do we wait and who is holding it's lock (you'd need to
add tracking of page lock owner but that shouldn't be too hard).

> I have few questions here.
> I guess process named jbd2/sdb1-8 is kjournald thread. But what is
  Yes.

> flush-8:16 process? Is it the kernel thread for periodically writing
> dirty pages to disk?
  Yes.

> Is it the case that these threads are running concurrently at certain
> time and are trying to get lock on same pages resulting into deadlock?
  It should not happen - they should always acquire page lock in
index-increasing order so that way deadlocks should be avoided...

								Honza
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html