Date: Thu, 29 Dec 2011 14:03:33 +0200 From: Kostik Belousov <kostikbel@gmail.com> To: Chris Rees <utisoft@gmail.com> Cc: hackers@freebsd.org Subject: Re: Checking for other kernel modules on load Message-ID: <20111229120333.GI50300@deviant.kiev.zoral.com.ua> In-Reply-To: <CADLo83-zRNXWyPrs-7MtPfd2uz=56HsWtDaAoFGx8=S=ChQhwQ@mail.gmail.com> References: <CADLo838QjrUunABB=3R_d6NO9bnNAcKXM%2BZt3DRam3RnOGnxGw@mail.gmail.com> <B8D5A1B2-4790-48CA-AAC3-D4333D52ECEB@gsoft.com.au> <CADLo8382uPC6YmreCz8irVuiOhSwc2axJTgQRpVJk-%2B0Win8rQ@mail.gmail.com> <20111228135641.GV50300@deviant.kiev.zoral.com.ua> <CADLo83-OBNWzY_r_oFmUBjkNoCpifJ0_u9dYN52YTZ69X06o4Q@mail.gmail.com> <20111228150023.GY50300@deviant.kiev.zoral.com.ua> <CADLo83-zRNXWyPrs-7MtPfd2uz=56HsWtDaAoFGx8=S=ChQhwQ@mail.gmail.com>
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--DBl6kzebMedsdQd1 Content-Type: text/plain; charset=koi8-r Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, Dec 29, 2011 at 11:46:57AM +0000, Chris Rees wrote: > 2011/12/28 Kostik Belousov <kostikbel@gmail.com>: > > On Wed, Dec 28, 2011 at 02:53:42PM +0000, Chris Rees wrote: > >> 2011/12/28 Kostik Belousov <kostikbel@gmail.com>: > >> > On Wed, Dec 28, 2011 at 12:23:58PM +0000, Chris Rees wrote: > >> >> On 28 December 2011 12:21, Daniel O'Connor <doconnor@gsoft.com.au> = wrote: > >> >> > > >> >> > On 28/12/2011, at 22:07, Chris Rees wrote: > >> >> >> Is there a simple way to check for existence of a driver? =9AI c= ould > >> >> >> even check for /dev/sndstat, though that doesn't seem elegant to= me... > >> >> > > >> >> > kldstat -v, but really /dev/sndstat seems simpler and just as eff= ective. > >> >> > > >> >> > >> >> Cheers-- I was thinking of a kernel-level function though. > >> >> > >> >> cognet@ suggested using modfind("sound"), I'll go with that. > >> > Obvious question is what the panic is. Checking for modules loaded is > >> > papering over some issue. > >> > >> True, although I figured that it was a simple conflict, possibly to do > >> with sndstat. > >> > >> Also, I'm getting panics with the following patch, whether sound is > >> loaded or not :) > >> > >> + =9Aif (modfind("sound") >=3D 0) > >> + =9A =9A{ > >> + =9A =9A =9Acmn_err (CE_WARN, "A conflicting sound driver is already = loaded"); > >> + =9A =9A =9Areturn EBUSY; > >> + =9A =9A} > >> + > >> > >> Is there a better way to handle such conflicts? > > > > You have missed the point. There is some bug in oss driver that causing > > the panic. Presumed 'conflict' cannot cause the harm itself, besides not > > allowing second driver to attach to the same device, and should not res= ult > > in panic. Trying to implement a half-measure that only covers the probl= em > > you do a mis-service. > > > > And you still did not provided the panic message. >=20 > I'm sorry, you're right. However, your guess was in fact correct; > make_dev was being called, which returned a null pointer because it > failed. >=20 > The patch at [1] stops the panic, however I was hoping that returning > EBUSY would abort loading the module... At the moment it loads the > module, and doesn't create the sndstat dev, which causes weird errors > with the oss binary commands. >=20 > Since this solves the panic and anyone should be able to work out from > the warning message what the problem is, AND this is a port that > apparently no-one else uses, should this be sufficient? >=20 > BTW, it only affects FreeBSD 9+, couldn't reproduce on my 8.2 dev > machine, but could once I upgraded it. On 8.2, there is no check in the devfs for duplicated cdev names, AFAIR. So you get absolutely undeterministic behaviour which driver is referenced by devfs node. > Chris >=20 > [1] http://www.bayofrum.net/~crees/patches/oss-patch-kernel-OS-FreeBSD-os= _freebsd.c I highly recommend to return error in case of any make_dev_p(9) failure, and not only EEXIST. --DBl6kzebMedsdQd1 Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.18 (FreeBSD) iEYEARECAAYFAk78VxQACgkQC3+MBN1Mb4hDRwCcD1N/Z24y1mPuAnUxAW/XGNPL MBUAoImdr6Z8q8zV/9W0E09grmJENPAZ =gpKx -----END PGP SIGNATURE----- --DBl6kzebMedsdQd1--
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