From: Lucio De Re <lucio@proxima.alt.za>
To: Fans of the OS Plan 9 from Bell Labs <9fans@9fans.net>
Subject: Re: [9fans] That deadlock, again
Date: Wed, 17 Nov 2010 08:45:00 +0200 [thread overview]
Message-ID: <20101117064500.GA3597@fangle.proxima.alt.za> (raw)
In-Reply-To: <4ee4b7c2dd207e953599fc618df2c456@gmx.de>
On Wed, Nov 17, 2010 at 06:22:33AM +0100, cinap_lenrek@gmx.de wrote:
>
> qpc is the just the caller of the last successfull *acquired* qlock.
> what we know is that the exportfs proc spins in the q->use taslock
> called by qlock() right? this already seems wired... q->use is held
> just long enougth to test q->locked and manipulate the queue. also
> sched() will avoid switching to another proc while we are holding tas
> locks.
>
I think I'm with you, probably not quite to the same depth of understanding.
> i would like to know which qlock is the kernel is trying to acquire
> on behalf of exportfs that is also reachable from the etherread4
> code.
>
... and from whatever the other proc is that also contributes to this
jam. I don't have the name right in front of me, but I will post it
separately. As far as I know it's always those two that interfere with
exportfs and usually together, only a short time apart.
> one could move:
>
> up->qpc = getcallerpc(&q);
>
> from qlock() before the lock(&q->use); so we can see from where that
> qlock gets called that hangs the exportfs call, or add another magic
> debug pointer (qpctry) to the proc stucture and print it in dumpaproc().
>
I think I'll do the latter; even though it's more complex, it can be a
useful debugging tool in future. I wouldn't leave in the kernel code,
but it would be worth being able to refer to it when the occasion arises.
How do you expect this qpctry to be initialised/set?
++L
next prev parent reply other threads:[~2010-11-17 6:45 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-11-16 4:21 lucio
2010-11-16 4:40 ` erik quanstrom
2010-11-16 5:03 ` lucio
2010-11-16 5:11 ` cinap_lenrek
2010-11-16 5:18 ` lucio
2010-11-16 5:28 ` cinap_lenrek
2010-11-16 6:47 ` Lucio De Re
2010-11-16 13:53 ` erik quanstrom
2010-11-16 18:03 ` lucio
2010-11-17 4:08 ` Lucio De Re
2010-11-17 4:18 ` erik quanstrom
2010-11-17 4:37 ` Lucio De Re
2010-11-17 4:43 ` erik quanstrom
2010-11-17 5:22 ` cinap_lenrek
2010-11-17 6:45 ` Lucio De Re [this message]
2010-11-17 7:03 ` Lucio De Re
2010-11-17 7:09 ` erik quanstrom
2010-11-17 5:33 ` cinap_lenrek
2010-11-17 6:48 ` Lucio De Re
2010-11-17 7:03 ` erik quanstrom
2010-11-17 14:40 ` Russ Cox
2010-11-18 5:50 Lucio De Re
2010-11-18 5:53 ` erik quanstrom
2010-11-18 8:11 ` Lucio De Re
2010-11-18 8:35 ` cinap_lenrek
2010-11-18 9:20 ` cinap_lenrek
2010-11-18 10:48 ` Lucio De Re
2010-11-18 15:10 ` erik quanstrom
2010-11-18 16:46 ` erik quanstrom
2010-11-18 18:01 ` Lucio De Re
2010-11-18 18:29 ` C H Forsyth
2010-11-18 18:23 ` Lucio De Re
2010-11-18 18:33 ` Lucio De Re
2010-11-18 18:43 ` erik quanstrom
2010-11-18 18:54 ` erik quanstrom
2010-11-18 19:01 ` Lucio De Re
2010-11-18 19:27 ` Lucio De Re
2010-11-18 18:03 ` Lucio De Re
2010-11-18 5:57 ` Lucio De Re
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=20101117064500.GA3597@fangle.proxima.alt.za \
--to=lucio@proxima.alt.za \
--cc=9fans@9fans.net \
/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).