From owner-freebsd-current@freebsd.org  Thu Jul  2 07:08:39 2015
Return-Path: <owner-freebsd-current@freebsd.org>
Delivered-To: freebsd-current@mailman.ysv.freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org
 [IPv6:2001:1900:2254:206a::19:1])
 by mailman.ysv.freebsd.org (Postfix) with ESMTP id B7296992B02
 for <freebsd-current@mailman.ysv.freebsd.org>;
 Thu,  2 Jul 2015 07:08:39 +0000 (UTC)
 (envelope-from kostikbel@gmail.com)
Received: from kib.kiev.ua (kib.kiev.ua [IPv6:2001:470:d5e7:1::1])
 (using TLSv1 with cipher DHE-RSA-CAMELLIA256-SHA (256/256 bits))
 (Client did not present a certificate)
 by mx1.freebsd.org (Postfix) with ESMTPS id 2C61E2AC9
 for <freebsd-current@freebsd.org>; Thu,  2 Jul 2015 07:08:38 +0000 (UTC)
 (envelope-from kostikbel@gmail.com)
Received: from tom.home (kostik@localhost [127.0.0.1])
 by kib.kiev.ua (8.14.9/8.14.9) with ESMTP id t6278WP7076283
 (version=TLSv1/SSLv3 cipher=DHE-RSA-CAMELLIA256-SHA bits=256 verify=NO);
 Thu, 2 Jul 2015 10:08:32 +0300 (EEST)
 (envelope-from kostikbel@gmail.com)
DKIM-Filter: OpenDKIM Filter v2.9.2 kib.kiev.ua t6278WP7076283
Received: (from kostik@localhost)
 by tom.home (8.14.9/8.14.9/Submit) id t6278SBV076282;
 Thu, 2 Jul 2015 10:08:28 +0300 (EEST)
 (envelope-from kostikbel@gmail.com)
X-Authentication-Warning: tom.home: kostik set sender to kostikbel@gmail.com
 using -f
Date: Thu, 2 Jul 2015 10:08:28 +0300
From: Konstantin Belousov <kostikbel@gmail.com>
To: Ryan Stone <rysto32@gmail.com>
Cc: Jack Vogel <jfvogel@gmail.com>,
 FreeBSD Current <freebsd-current@freebsd.org>
Subject: Re: How should a driver shutdown a taskqueue on detach?
Message-ID: <20150702070828.GH2080@kib.kiev.ua>
References: <CAFMmRNxLV0Uk9iT+U8rrPvn6aanSfEA6p577McM=_4xypaZr5w@mail.gmail.com>
 <CAFOYbckF7brPikTPaf+Zhdm-R9d0WzygY9-eUxnrmi3p+BFBoQ@mail.gmail.com>
 <CAFMmRNzLL-K0kw_cj==kWpiocOcBLzxU2o6ONGaZRiv5tdSHxQ@mail.gmail.com>
 <20150701213241.GG2080@kib.kiev.ua>
 <CAFMmRNyeEp0gccRAspkJNT_tFWZvJWEczNitB8nCyOzSWKZBWA@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CAFMmRNyeEp0gccRAspkJNT_tFWZvJWEczNitB8nCyOzSWKZBWA@mail.gmail.com>
User-Agent: Mutt/1.5.23 (2014-03-12)
X-Spam-Status: No, score=-2.0 required=5.0 tests=ALL_TRUSTED,BAYES_00,
 DKIM_ADSP_CUSTOM_MED,FREEMAIL_FROM,NML_ADSP_CUSTOM_MED autolearn=no
 autolearn_force=no version=3.4.1
X-Spam-Checker-Version: SpamAssassin 3.4.1 (2015-04-28) on tom.home
X-BeenThere: freebsd-current@freebsd.org
X-Mailman-Version: 2.1.20
Precedence: list
List-Id: Discussions about the use of FreeBSD-current
 <freebsd-current.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/options/freebsd-current>, 
 <mailto:freebsd-current-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-current/>
List-Post: <mailto:freebsd-current@freebsd.org>
List-Help: <mailto:freebsd-current-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-current>,
 <mailto:freebsd-current-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Thu, 02 Jul 2015 07:08:39 -0000

On Wed, Jul 01, 2015 at 06:28:49PM -0400, Ryan Stone wrote:
> On Wed, Jul 1, 2015 at 5:32 PM, Konstantin Belousov <kostikbel@gmail.com>
> wrote:
> 
> > Do you mean, you want some KPI like
> >         boolean taskqueue_is_draining(struct taskqueue *p);
> > so that e.g. executed task could see if it is executing in the
> > shutdown state ?
> 
> 
> I'd prefer a KPI that stops a taskqueue from accepting new tasks (and drops
> attempts to enqueue on the floor).  Then I could do something like:
> 
> taskqueue_stop()
> disable_interrupts()
> taskqueue_drain_all()
> taskqueue_free()

Having taskqueue_enqueue() which could silently (?) not enqueue the given
task is huge and IMO risky change to the KPI.  If doing it, I think
that there should be a new function to enqueue, which is allowed to
fail, unlike taskqueue_enqueue().

BTW, the man page for taskqueue(9) is wrong, taskqueue_enqueue(9)
always succeed now and always returns 0 (ignoring the ushort overflow).