Date: Tue, 8 Jan 2013 05:00:22 +0200 From: Konstantin Belousov <kostikbel@gmail.com> To: Oleksandr Tymoshenko <gonzo@freebsd.org> Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r245147 - head/sys/arm/include Message-ID: <20130108030022.GC82219@kib.kiev.ua> In-Reply-To: <201301080240.r082eKVq080302@svn.freebsd.org> References: <201301080240.r082eKVq080302@svn.freebsd.org>
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--+plSmdOTvOCX/8Oy Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, Jan 08, 2013 at 02:40:20AM +0000, Oleksandr Tymoshenko wrote: > Author: gonzo > Date: Tue Jan 8 02:40:20 2013 > New Revision: 245147 > URL: http://svnweb.freebsd.org/changeset/base/245147 >=20 > Log: > Switch default cache type for ARMv6/ARMv7 from write-through to > writeback-writeallocate Could you, please, describe how this is supposed to work. Assume that a process mapped the same file page at two different addresses, both read-write, and writes to both mappings. Usermode code does not consider the need to flush caches or synchronize writes into non-overlapping regions, usually. Would it break, i.e. could the values appear in the page which were never written to it ? Another similar question, sf buffers on ARM flush the cache on sf_buf_free() (sometimes). If the page, for which the sf buffer is created, mapped into the userspace read-write, could it be that a value appears that was never written ? Note that sf buffers are used e.g. by uiomove_fromphys(). --+plSmdOTvOCX/8Oy Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.19 (FreeBSD) iQIcBAEBAgAGBQJQ64vFAAoJEJDCuSvBvK1BfEwP/A4xXCfW82HgQHNeT5mxlRp6 /Gw2UD7T7c6+3/1cQUDN10hrlv52hVI8et30Q0S5/2rjB3YeQ/SROHwzXRNCtOgI JM/sAw3LS6ksXvMGzqsUK53676G/Oso4C+bYLUJELkIihhXxDvpscbI7O2s1VLBZ fMjSuiMpMhHypV2+Y48RP5EdsDXbVNkloMvifHEcBaN+HePK4qkQHZgnAyDoz3+E YC+FOdORExzSYUyuBYXEWLEMtNBkHKJhMaGIXaqzCnuyO2bvY5uW91MQu+rk/iCy DpC3cnIcFlnRX6WdZQoOHoVJDXl9jYaQynMZTDfbM9s1qTbUd5H+wjb+LXcw8C4Y j6ovmaL8CnEU/i7VcWlodwib/ZoCiBv5hjFILi3A08kfUKtiM8iijEyVe8YUALR2 AbkRRpM6Ce8Obu+T+/BXO9VX7UQC5ayyqmHSBE8NI4HlBjKAWguR+53WjmxDhbf7 R+Mquegi8zVEZ7/gnwdv1sleukheb3QfJAXE6WGWEfxEtSj7sqCC8UozBupIKRe7 zVUzkKpdcNCcvUi6hiYYGH2XUMzfa9cyY2yFIRAF9HCiHn2/zQC2wLQ1ZqcPwqur LHQwf02mbRz87k+P0V61FxkJhUrUFe6s36GlyeoPO4V6t5ImTzFOsGpI9p/VWKXL 4n+lb/EuD0RfkpdKnKyk =f1Yd -----END PGP SIGNATURE----- --+plSmdOTvOCX/8Oy--
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