From owner-svn-src-all@FreeBSD.ORG Thu May 3 13:27:27 2012 Return-Path: Delivered-To: svn-src-all@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id 6A1A0106564A; Thu, 3 May 2012 13:27:27 +0000 (UTC) (envelope-from kostikbel@gmail.com) Received: from mail.zoral.com.ua (mx0.zoral.com.ua [91.193.166.200]) by mx1.freebsd.org (Postfix) with ESMTP id 0019D8FC16; Thu, 3 May 2012 13:27:26 +0000 (UTC) Received: from skuns.kiev.zoral.com.ua (localhost [127.0.0.1]) by mail.zoral.com.ua (8.14.2/8.14.2) with ESMTP id q43DRGQZ098646; Thu, 3 May 2012 16:27:16 +0300 (EEST) (envelope-from kostikbel@gmail.com) Received: from deviant.kiev.zoral.com.ua (kostik@localhost [127.0.0.1]) by deviant.kiev.zoral.com.ua (8.14.5/8.14.5) with ESMTP id q43DRFhA039663; Thu, 3 May 2012 16:27:15 +0300 (EEST) (envelope-from kostikbel@gmail.com) Received: (from kostik@localhost) by deviant.kiev.zoral.com.ua (8.14.5/8.14.5/Submit) id q43DRFHK039662; Thu, 3 May 2012 16:27:15 +0300 (EEST) (envelope-from kostikbel@gmail.com) X-Authentication-Warning: deviant.kiev.zoral.com.ua: kostik set sender to kostikbel@gmail.com using -f Date: Thu, 3 May 2012 16:27:15 +0300 From: Konstantin Belousov To: Attilio Rao Message-ID: <20120503132715.GN2358@deviant.kiev.zoral.com.ua> References: <201205031038.q43Ac2eZ032779@svn.freebsd.org> <20120503114913.GJ2358@deviant.kiev.zoral.com.ua> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="v0lslBALPq2/Zk2u" Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.3i X-Virus-Scanned: clamav-milter 0.95.2 at skuns.kiev.zoral.com.ua X-Virus-Status: Clean X-Spam-Status: No, score=-4.0 required=5.0 tests=ALL_TRUSTED,AWL,BAYES_00 autolearn=ham version=3.2.5 X-Spam-Checker-Version: SpamAssassin 3.2.5 (2008-06-10) on skuns.kiev.zoral.com.ua Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org, christian.esken@trivago.com Subject: Re: svn commit: r234952 - in head/sys: kern sys X-BeenThere: svn-src-all@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: "SVN commit messages for the entire src tree \(except for " user" and " projects" \)" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 03 May 2012 13:27:27 -0000 --v0lslBALPq2/Zk2u Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, May 03, 2012 at 02:14:20PM +0100, Attilio Rao wrote: > 2012/5/3, Konstantin Belousov : > > On Thu, May 03, 2012 at 12:02:08PM +0100, Attilio Rao wrote: > >> 2012/5/3, Konstantin Belousov : > >> > Author: kib > >> > Date: Thu May 3 10:38:02 2012 > >> > New Revision: 234952 > >> > URL: http://svn.freebsd.org/changeset/base/234952 > >> > > >> > Log: > >> > When callout_reset_on() cannot immediately migrate a callout since= it > >> > is running on other cpu, the CALLOUT_PENDING flag is temporarily > >> > cleared. Then, callout_stop() on this, in fact active, callout fai= ls > >> > because CALLOUT_PENDING is not set, and callout_stop() returns 0. > >> > > >> > Now, in sleepq_check_timeout(), the failed callout_stop() causes t= he > >> > sleepq code to execute mi_switch() without even setting the wmesg, > >> > since the switch-out is supposed to be transient. In fact, the thr= ead > >> > is put off the CPU for full timeout interval, instead of being put= on > >> > runq immediately. Until timeout fires, the process is unkillable = for > >> > obvious reasons. > >> > > >> > Fix this by marking the migrating callouts with CALLOUT_DFRMIGRATI= ON > >> > flag. The flag is cleared by callout_stop_safe() when the function > >> > detects a migration, besides returning the success. The softclock() > >> > rechecks the flag for migrating callout and cancels its execution = if > >> > the flag was cleared meantime. > >> > >> Can you please clarify why you cannot simply drop the deferred > >> migration in the case !CALLOUT_PENDING in callout_stop_safe()? > > > > I probably can, I think I went with the route of committed patch > > because it is slightly less work. Also, the comment in the while() > > loop suggested me to rely on softclock. >=20 > I don't think this is more work at all, the attached patch > (pre-r234952, untested) should address it properly in few than 10 > lines: > http://www.freebsd.org/~attilio/callout_cancel_mig_stop.patch >=20 > without the need to add further flags and re-using existing mechanisms. (cc->cc_curr !=3D c) is not the case which caused the issue. It might be needed to treatened this way, but the reported case is opposite. --v0lslBALPq2/Zk2u Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (FreeBSD) iEYEARECAAYFAk+ih7MACgkQC3+MBN1Mb4gtdACfUK1QNh57ZBpu2xpbPOIiuSEZ 8hEAn1EF1Yy77YYiz+TVmihpyg9JpZNj =uXBb -----END PGP SIGNATURE----- --v0lslBALPq2/Zk2u--