From mboxrd@z Thu Jan  1 00:00:00 1970
From: compudj@krystal.dyndns.org (Mathieu Desnoyers)
Date: Sun, 20 Feb 2011 10:17:45 -0500
Subject: [ltt-dev] [UST PATCH] Fix the once in a while freeze of
	the	tests
In-Reply-To: <BLU0-SMTP7877677646A5D05A9F129C96D60@phx.gbl>
References: <1298065013-9872-1-git-send-email-yannick.brosseau@gmail.com>
	<BLU0-SMTP7877677646A5D05A9F129C96D60@phx.gbl>
Message-ID: <BLU0-SMTP64210ABE98921B8359362F96D60@phx.gbl>

* Mathieu Desnoyers (compudj at krystal.dyndns.org) wrote:
> * Yannick Brosseau (yannick.brosseau at gmail.com) wrote:
> > Sometimes, the thread in the read function would lock the pipe so the
> > setlinebuf would freeze on it. Set the linebuf before we create the
> > thread to fix this deadlock
> 
> Can you update the description to show which locks are involved in this
> deadlock scenario ? E.g.
> 
> - CPU A               - CPU B
> 
> function              function
> lock A (taken)        lock B (taken)
> lock B (waiting)
>                       lock A (waiting)  <-- deadlock
> 
> Or show it with the lock chain dependency analysis. But it's important
> to have this information along with this kind of fix.

Hrm, ok I looked at tap.c, and it's not a deadlock at all: it's rather
that the _tap_comment_stdout thread can start using pipe_r_file when it
is still uninitialized.

I'll update the comment and pull the patch.

Thanks,

Mathieu

> 
> Thanks,
> 
> Mathieu
> > 
> > Signed-off-by: Yannick Brosseau <yannick.brosseau at gmail.com>
> > ---
> >  tests/tap.c |    5 ++++-
> >  1 files changed, 4 insertions(+), 1 deletions(-)
> > 
> > diff --git a/tests/tap.c b/tests/tap.c
> > index a54fd17..4bb695e 100644
> > --- a/tests/tap.c
> > +++ b/tests/tap.c
> > @@ -58,6 +58,9 @@ static void tap_comment_stdout(void)
> >  		goto close_pipe;
> >  	}
> >  
> > +	/* Set it before we create the reading thread */
> > +	setlinebuf(pipe_r_file);
> > +
> >  	stdout_fileno = fileno(stdout);
> >  	if (stdout_fileno < 0) {
> >  		perror("# Couldn't get fileno for stdout!?");
> > @@ -112,7 +115,7 @@ static void tap_comment_stdout(void)
> >  
> >  	setlinebuf(stdout);
> >  	setlinebuf(stderr);
> > -	setlinebuf(pipe_r_file);
> > +
> >  
> >  	return;
> >  
> > -- 
> > 1.7.2.3
> > 
> > 
> > _______________________________________________
> > ltt-dev mailing list
> > ltt-dev at lists.casi.polymtl.ca
> > http://lists.casi.polymtl.ca/cgi-bin/mailman/listinfo/ltt-dev
> > 
> 
> -- 
> Mathieu Desnoyers
> Operating System Efficiency R&D Consultant
> EfficiOS Inc.
> http://www.efficios.com
> 
> _______________________________________________
> ltt-dev mailing list
> ltt-dev at lists.casi.polymtl.ca
> http://lists.casi.polymtl.ca/cgi-bin/mailman/listinfo/ltt-dev
> 

-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com