Date: Mon, 9 Feb 2009 22:01:40 -0800 From: Alfred Perlstein <alfred@freebsd.org> To: "M. Warner Losh" <imp@bsdimp.com> Cc: pyunyh@gmail.com, 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: <20090210060140.GY68801@elvis.mu.org> In-Reply-To: <20090209.160117.-1183815561.imp@bsdimp.com> References: <20090202051421.GE43513@michelle.cdnetworks.co.kr> <20090201.222119.-1303462184.imp@bsdimp.com> <20090209223439.GP68801@elvis.mu.org> <20090209.160117.-1183815561.imp@bsdimp.com>
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* M. Warner Losh <imp@bsdimp.com> [090209 15:03] wrote:
> In message: <20090209223439.GP68801@elvis.mu.org>
> Alfred Perlstein <alfred@FreeBSD.org> writes:
> : * M. Warner Losh <imp@bsdimp.com> [090201 21:24] wrote:
> : > 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().
> :
> : Can some asserts be added?
> :
> : Maybe under an additonal ifdef considering usb2 for a short time?
>
> Are these not sufficient:
>
> int
> device_probe_child(device_t dev, device_t child)
> {
> devclass_t dc;
> driverlink_t best = NULL;
> driverlink_t dl;
> int result, pri = 0;
> int hasclass = (child->devclass != NULL);
>
> GIANT_REQUIRED;
> ...
It sounded like usb2 was calling it without Giant...
--
- Alfred Perlstein
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