Date: Sun, 01 Feb 2009 22:21:19 -0700 (MST) From: "M. Warner Losh" <imp@bsdimp.com> To: pyunyh@gmail.com Cc: src-committers@freebsd.org, thompsa@freebsd.org, svn-src-user@freebsd.org Subject: Re: svn commit: r187978 - user/thompsa/usb/sys/dev/usb2/ethernet Message-ID: <20090201.222119.-1303462184.imp@bsdimp.com> In-Reply-To: <20090202051421.GE43513@michelle.cdnetworks.co.kr> References: <20090202044416.GC43513@michelle.cdnetworks.co.kr> <20090201.215218.1013608033.imp@bsdimp.com> <20090202051421.GE43513@michelle.cdnetworks.co.kr>
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In message: <20090202051421.GE43513@michelle.cdnetworks.co.kr>
Pyun YongHyeon <pyunyh@gmail.com> writes:
: On Sun, Feb 01, 2009 at 09:52:18PM -0700, M. Warner Losh wrote:
: > In message: <20090202044416.GC43513@michelle.cdnetworks.co.kr>
: > Pyun YongHyeon <pyunyh@gmail.com> writes:
: > : On Sun, Feb 01, 2009 at 08:36:18PM -0700, M. Warner Losh wrote:
: > : > In message: <20090201213749.GJ32503@citylink.fud.org.nz>
: > : > Andrew Thompson <thompsa@FreeBSD.org> writes:
: > : > : On Sun, Feb 01, 2009 at 02:28:08PM -0700, M. Warner Losh wrote:
: > : > : > In message: <200902010650.n116obU1045871@svn.freebsd.org>
: > : > : > Andrew Thompson <thompsa@FreeBSD.org> writes:
: > : > : > : + locked = mtx_owned(&sc->sc_mtx);
: > : > : > : + if (!locked)
: > : > : > : + AUE_LOCK(sc);
: > : > : >
: > : > : > You do know this is racy, right?
: > : > :
: > : > : Yea... It only get called unlocked during mii probe+attach so its fine.
: > : > : I havnt actaully checked if its ok to hold a mutex during
: > : > : mii_phy_probe() which would make this go away.
: > : >
: > : > You hold GIANT when probe+attach, which means I think you can't
: > :
: > : AFAIK this is not true on USB2 and I think this is reason why
: > : it have to lock/unlock dance in probe/attach.
: >
: > It is a newbus requirement that all probe/attach routines have to be
: > called with GIANT held.
: >
:
: If this can be done on USB2 it would greatly simplify MII attach
: part as well as locks used in MII access routines in all USB2
: ethernet drivers. I vaguely remember I asked for this to HPS, but
: he seem to forget about it.
I'll take a look into the matter in more detail. It is an absolute
requirement of newbus at the moment that any call to
device_probe_and_attach(), including bus_generic_attach().
Warner
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