From owner-freebsd-current@FreeBSD.ORG Mon Feb 18 15:08:25 2013 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.freebsd.org (mx1.FreeBSD.org [8.8.178.115]) by hub.freebsd.org (Postfix) with ESMTP id 5F112A12 for ; Mon, 18 Feb 2013 15:08:25 +0000 (UTC) (envelope-from kostikbel@gmail.com) Received: from kib.kiev.ua (kib.kiev.ua [IPv6:2001:470:d5e7:1::1]) by mx1.freebsd.org (Postfix) with ESMTP id B0EAD295 for ; Mon, 18 Feb 2013 15:08:24 +0000 (UTC) Received: from tom.home (kostik@localhost [127.0.0.1]) by kib.kiev.ua (8.14.6/8.14.6) with ESMTP id r1IF8AUR019342; Mon, 18 Feb 2013 17:08:10 +0200 (EET) (envelope-from kostikbel@gmail.com) DKIM-Filter: OpenDKIM Filter v2.7.4 kib.kiev.ua r1IF8AUR019342 Received: (from kostik@localhost) by tom.home (8.14.6/8.14.6/Submit) id r1IF8AFE019341; Mon, 18 Feb 2013 17:08:10 +0200 (EET) (envelope-from kostikbel@gmail.com) X-Authentication-Warning: tom.home: kostik set sender to kostikbel@gmail.com using -f Date: Mon, 18 Feb 2013 17:08:09 +0200 From: Konstantin Belousov To: Svatopluk Kraus Subject: Re: [patch] i386 pmap sysmaps_pcpu[] atomic access Message-ID: <20130218150809.GG2598@kib.kiev.ua> References: MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="GdbWtwDHkcXqP16f" Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) 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 version=3.3.2 X-Spam-Checker-Version: SpamAssassin 3.3.2 (2011-06-06) on tom.home Cc: freebsd-current@freebsd.org X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 18 Feb 2013 15:08:25 -0000 --GdbWtwDHkcXqP16f Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Feb 18, 2013 at 01:44:35PM +0100, Svatopluk Kraus wrote: > Hi, >=20 > the access to sysmaps_pcpu[] should be atomic with respect to > thread migration. Otherwise, a sysmaps for one CPU can be stolen by > another CPU and the purpose of per CPU sysmaps is broken. A patch is > enclosed. And, what are the problem caused by the 'otherwise' ? I do not see any. Really, taking the mutex while bind to a CPU could be deadlock-prone under some situations. This was discussed at least one more time. Might be, a comment saying that there is no issue should be added. >=20 > Svata >=20 > Index: sys/i386/i386/pmap.c > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > --- sys/i386/i386/pmap.c (revision 246831) > +++ sys/i386/i386/pmap.c (working copy) > @@ -4146,11 +4146,11 @@ > { > struct sysmaps *sysmaps; >=20 > + sched_pin(); > sysmaps =3D &sysmaps_pcpu[PCPU_GET(cpuid)]; > mtx_lock(&sysmaps->lock); > if (*sysmaps->CMAP2) > panic("pmap_zero_page: CMAP2 busy"); > - sched_pin(); > *sysmaps->CMAP2 =3D PG_V | PG_RW | VM_PAGE_TO_PHYS(m) | PG_A | PG_M | > pmap_cache_bits(m->md.pat_mode, 0); > invlcaddr(sysmaps->CADDR2); > @@ -4171,11 +4171,11 @@ > { > struct sysmaps *sysmaps; >=20 > + sched_pin(); > sysmaps =3D &sysmaps_pcpu[PCPU_GET(cpuid)]; > mtx_lock(&sysmaps->lock); > if (*sysmaps->CMAP2) > panic("pmap_zero_page_area: CMAP2 busy"); > - sched_pin(); > *sysmaps->CMAP2 =3D PG_V | PG_RW | VM_PAGE_TO_PHYS(m) | PG_A | PG_M | > pmap_cache_bits(m->md.pat_mode, 0); > invlcaddr(sysmaps->CADDR2); > @@ -4220,13 +4220,13 @@ > { > struct sysmaps *sysmaps; >=20 > + sched_pin(); > sysmaps =3D &sysmaps_pcpu[PCPU_GET(cpuid)]; > mtx_lock(&sysmaps->lock); > if (*sysmaps->CMAP1) > panic("pmap_copy_page: CMAP1 busy"); > if (*sysmaps->CMAP2) > panic("pmap_copy_page: CMAP2 busy"); > - sched_pin(); > invlpg((u_int)sysmaps->CADDR1); > invlpg((u_int)sysmaps->CADDR2); > *sysmaps->CMAP1 =3D PG_V | VM_PAGE_TO_PHYS(src) | PG_A | > @@ -5072,11 +5072,11 @@ > vm_offset_t sva, eva; >=20 > if ((cpu_feature & CPUID_CLFSH) !=3D 0) { > + sched_pin(); > sysmaps =3D &sysmaps_pcpu[PCPU_GET(cpuid)]; > mtx_lock(&sysmaps->lock); > if (*sysmaps->CMAP2) > panic("pmap_flush_page: CMAP2 busy"); > - sched_pin(); > *sysmaps->CMAP2 =3D PG_V | PG_RW | VM_PAGE_TO_PHYS(m) | > PG_A | PG_M | pmap_cache_bits(m->md.pat_mode, 0); > invlcaddr(sysmaps->CADDR2); > _______________________________________________ > freebsd-current@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-current > To unsubscribe, send any mail to "freebsd-current-unsubscribe@freebsd.org" --GdbWtwDHkcXqP16f Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.19 (FreeBSD) iQIcBAEBAgAGBQJRIkPZAAoJEJDCuSvBvK1B5JcP/RIJxvumbc5eMO4xE8z19rT/ jDjkcKCRUQMKkc0D2NrtI3La1jyj6Hgen7hL5HE4rZBZPm57pNXbF/L4rf7hCQtt yg0AJddHI+ZpBIhoDGpUTZA7P476hFckwcDe++3+eOe104JFVs4QbhnfjI3Duc2K fa+epN4gWeeKXI7GSm64T9XNfsSJXzhRq+fgvN6U5dTTY45oiz/LXqO7/Jz7yZVR gaGoIgSBWxaproCm0hvXCI5dQ0BHfimgvHQgtUGI9t9JyTVPVymjKMdcDUk55ksc e1v977j8nECWjlR0Jhq9WPeQaSVy/M0J12BJtdoRZL5Z4IEst8vd/a8s8XA98dV/ 77LDD6E6KJXhCrMG0TphEm1c2Kh1ZWn3YyjCFEUVpjJ4K7IUfK7J3sRKvCeilTzk bm2mQnkCvEMw7vsri/AZApBnNkCsYBDMj/B4PezfDIeSqEN0547MxpITLp43QwiU viLriUs9hPOrIdOQ7jgKaSL7Gr+G+/zHW4hBdOwhHi7TWcpov0NZbdJiAQTLeFJr v9NLglj2czAqAcspBf28UNm03y8M0ClItCC3MOTR936RLzgntKXcliFowcWKnW0b YoiODZECGTTA9DFB0GQtb28nrTQC3cXcQSVxAfz1iKD0ThqA5/r3CNV48+diOa+t I8JhVjY4CGJCexr46TCX =xOUl -----END PGP SIGNATURE----- --GdbWtwDHkcXqP16f--