Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751813Ab0LQIUT (ORCPT ); Fri, 17 Dec 2010 03:20:19 -0500 Received: from fmmailgate02.web.de ([217.72.192.227]:46436 "EHLO fmmailgate02.web.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750918Ab0LQIUS (ORCPT ); Fri, 17 Dec 2010 03:20:18 -0500 Message-ID: <4D0B1CD9.5060601@web.de> Date: Fri, 17 Dec 2010 09:18:33 +0100 From: Jan Kiszka User-Agent: Mozilla/5.0 (X11; U; Linux i686 (x86_64); de; rv:1.8.1.12) Gecko/20080226 SUSE/2.0.0.12-1.1 Thunderbird/2.0.0.12 Mnenhy/0.7.5.666 MIME-Version: 1.0 To: Thomas Gleixner CC: Avi Kivity , Marcelo Tosatti , linux-kernel@vger.kernel.org, kvm , Tom Lyon , Alex Williamson , "Michael S. Tsirkin" , Jan Kiszka Subject: Re: [PATCH v3 2/4] genirq: Inform handler about line sharing state References: <4D0A75E3.3090900@web.de> In-Reply-To: <4D0A75E3.3090900@web.de> X-Enigmail-Version: 1.1.2 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enig267336D61C8FA0F7F603BD7E" X-Provags-ID: V01U2FsdGVkX1+Pflteipq8JOXC6ahPN839/PaemuBWk7iGmMDr v+gzeEz00sRh5Z9iZ3LgBS5iqDFYsUeQO9Sm/rUYMD95LjF/t0 Ex5piN+cY= Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2264 Lines: 58 This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enig267336D61C8FA0F7F603BD7E Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Am 16.12.2010 21:26, Jan Kiszka wrote: > Am 16.12.2010 14:13, Thomas Gleixner wrote: >> On Mon, 13 Dec 2010, Jan Kiszka wrote: >>> + if (old_action && (old_action->flags & IRQF_ADAPTIVE) && >>> + !(desc->irq_data.drv_status & IRQS_SHARED)) { >>> + /* >>> + * Signal the old handler that is has to switch to shareable >>> + * handling mode. Disable the line to avoid any conflict with >>> + * a real IRQ. >>> + */ >>> + disable_irq(irq); >> >> This is weird, really. I thought you wanted to avoid waiting for the >> threaded handler to finish if it's on the fly. So this should be >> disable_irq_nosync() or did you change your mind ? >=20 > No, I did not. I wanted to avoid that we set MAKE_SHAREABLE while there= > might be another IRQ in flight. The handler that is called due to a rea= l > IRQ might misinterpret MAKE_SHAREABLE as "there is no real event" and > perform the wrong steps (at least the current implementation for KVM wo= uld). Actually, the requirement we have to fulfill here is to avoid that the hardirq handler sees !SHARED while the threaded one reads "SHARED". To achieve this without disabling the line, I'm still searching for a way to couple the sharing state of associated hard and threaded handler runs - but I think there is no reliable association, is there? Jan --------------enig267336D61C8FA0F7F603BD7E Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.15 (GNU/Linux) Comment: Using GnuPG with SUSE - http://enigmail.mozdev.org/ iEYEARECAAYFAk0LHNwACgkQitSsb3rl5xTS2gCgth+pwz/KbEz+MvV/JYxYntp8 I7QAoKdmTWE8xoNfZbPjQfY4Fyltr8SK =QrZk -----END PGP SIGNATURE----- --------------enig267336D61C8FA0F7F603BD7E-- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/