Re: [PATCH v3 3/8] coccicheck: enable parmap support

From: Julia Lawall <julia.lawall@lip6.fr>
To: "Luis R. Rodriguez" <mcgrof@kernel.org>
Cc: Julia Lawall <julia.lawall@lip6.fr>,
	Gilles.Muller@lip6.fr, nicolas.palix@imag.fr, mmarek@suse.com,
	linux-kernel@vger.kernel.org, akpm@linux-foundation.org,
	gregkh@linuxfoundation.org, markivx@codeaurora.org,
	stephen.boyd@linaro.org, zohar@linux.vnet.ibm.com,
	broonie@kernel.org, ming.lei@canonical.com, tiwai@suse.de,
	johannes@sipsolutions.net, chunkeey@googlemail.com,
	hauke@hauke-m.de, jwboyer@fedoraproject.org,
	dmitry.torokhov@gmail.com, dwmw2@infradead.org, jslaby@suse.com,
	torvalds@linux-foundation.org, deepa.kernel@gmail.com,
	cocci@systeme.lip6.fr
Subject: Re: [PATCH v3 3/8] coccicheck: enable parmap support
Date: Tue, 21 Jun 2016 23:10:00 +0200 (CEST)	[thread overview]
Message-ID: <alpine.DEB.2.02.1606212308580.2040@localhost6.localdomain6> (raw)
In-Reply-To: <20160621205441.GW25646@wotan.suse.de>

On Tue, 21 Jun 2016, Luis R. Rodriguez wrote:

> On Tue, Jun 21, 2016 at 10:43:04PM +0200, Julia Lawall wrote:
> > 
> > 
> > On Tue, 21 Jun 2016, Luis R. Rodriguez wrote:
> > 
> > > On Tue, Jun 21, 2016 at 10:17:38PM +0200, Julia Lawall wrote:
> > > > 
> > > > 
> > > > On Tue, 21 Jun 2016, Luis R. Rodriguez wrote:
> > > > 
> > > > > Coccinelle has had parmap support since 1.0.2, this means
> > > > > it supports --jobs, enabling built-in multithreaded functionality,
> > > > > instead of needing one to script it out. Just look for --jobs
> > > > > in the help output to determine if this is supported.
> > > > > 
> > > > > Also enable the load balancing to be dynamic, so that if a
> > > > > thread finishes early we keep feeding it.
> > > > > 
> > > > > Note: now that we have all things handled for us, redirect stderr to
> > > > > stdout as well to capture any possible errors or warnings issued by
> > > > > coccinelle.
> > > > > 
> > > > > If --jobs is not supported we fallback to the old mechanism.
> > > > > This also now accepts DEBUG_FILE= to specify where you want
> > > > > stderr to be redirected to, by default we redirect stderr to
> > > > > /dev/null.
> > > > 
> > > > Why do you want to do something different for standard error in the parmap 
> > > > and nonparmap case?
> > > 
> > > We should just deprecate non-parmap later.
> > 
> > that's not really getting at the point.  I like the DEBUG_FILE= solution.  
> > I don't like merging stderr and stdout.  So you've put what to my mind is 
> > the good solution only in the deprecated case (to my understanding of 
> > the commit message).
> 
> stderr is not being merged to stdout though. By default stderr goes to /dev/null
> and if you want it you specify a DEBUG_FILE.

Above it says:

Note: now that we have all things handled for us, redirect stderr to 
stdout as well to capture any possible errors or warnings issued by 
coccinelle.

If DEBUG_FILE is an option for the parmap case, it should be mentioned 
there too.

julia

> 
> What will be deprecated has no clean solution for any of this and its unclear
> exactly what happens given separate processes are run in the background
> and we just wait.
> 
>   Luis
> 