From: Theodore Ts'o <tytso@mit.edu>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Staffan Tjernstrom <stjernstrom@eagleseven.com>,
"linux-rt-users@vger.kernel.org" <linux-rt-users@vger.kernel.org>,
"tglx@linutronix.de" <tglx@linutronix.de>,
"C.Emde@osadl.org" <C.Emde@osadl.org>,
"jkacur@redhat.com" <jkacur@redhat.com>
Subject: Re: Observed deadlock in ext4 under 3.2.23-rt37 & 3.2.33-rt50
Date: Thu, 3 Jan 2013 09:18:37 -0500 [thread overview]
Message-ID: <20130103141837.GC16895@thunk.org> (raw)
In-Reply-To: <1357219291.10284.21.camel@gandalf.local.home>
On Thu, Jan 03, 2013 at 08:21:31AM -0500, Steven Rostedt wrote:
> Anytime you have something that does the following in order to break
> lock ordering:
>
> repeat:
> lock(A);
> <do something>
> if (!trylock(B)) {
> unlock(A);
> cpu_relax();
> goto repeat;
> }
>
>
> We can live lock, because spinlocks in -rt turn into a mutex. Thus, the
> holder of lock B may not be on another CPU but actually on the current
> CPU and is waiting for the process that is in this loop. If that process
> happens to be an RT task, then the system stops.
Good point, but I'm prety sure we don't have any kind of trylock loops
in either fs/ext4 or fs/jbd2, though.
- Ted
next prev parent reply other threads:[~2013-01-03 14:18 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <7A2FC0CD30EF4745AE15F485252D38AC2F45A70C9A@clark>
2013-01-03 3:09 ` Observed deadlock in ext4 under 3.2.23-rt37 & 3.2.33-rt50 Steven Rostedt
2013-01-03 4:22 ` Theodore Ts'o
2013-01-03 13:21 ` Steven Rostedt
2013-01-03 14:18 ` Theodore Ts'o [this message]
2013-01-03 14:36 ` Staffan Tjernstrom
2013-01-03 15:36 ` Theodore Ts'o
2013-01-03 15:52 ` Staffan Tjernstrom
2013-01-03 15:35 ` Steven Rostedt
2013-01-03 14:29 ` Staffan Tjernstrom
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=20130103141837.GC16895@thunk.org \
--to=tytso@mit.edu \
--cc=C.Emde@osadl.org \
--cc=jkacur@redhat.com \
--cc=linux-rt-users@vger.kernel.org \
--cc=rostedt@goodmis.org \
--cc=stjernstrom@eagleseven.com \
--cc=tglx@linutronix.de \
/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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.