Date: Thu, 29 Dec 2011 15:35:16 +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: <20111229133516.GJ50300@deviant.kiev.zoral.com.ua> In-Reply-To: <CADLo83-Dm8_k79zsfxJ_X6RW04AawcZaATcvZ86B3v26k32EmQ@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> <20111229120333.GI50300@deviant.kiev.zoral.com.ua> <CADLo83-Dm8_k79zsfxJ_X6RW04AawcZaATcvZ86B3v26k32EmQ@mail.gmail.com>
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--e/SfQGHLOMWAfGD8 Content-Type: text/plain; charset=koi8-r Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, Dec 29, 2011 at 12:53:19PM +0000, Chris Rees wrote: > 2011/12/29 Kostik Belousov <kostikbel@gmail.com>: > > 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.a= u> wrote: > >> >> >> > > >> >> >> > On 28/12/2011, at 22:07, Chris Rees wrote: > >> >> >> >> Is there a simple way to check for existence of a driver? =9A= I could > >> >> >> >> even check for /dev/sndstat, though that doesn't seem elegant= to me... > >> >> >> > > >> >> >> > kldstat -v, but really /dev/sndstat seems simpler and just as = effective. > >> >> >> > > >> >> >> > >> >> >> 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 loade= d 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 alrea= dy 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 caus= ing > >> > the panic. Presumed 'conflict' cannot cause the harm itself, besides= not > >> > allowing second driver to attach to the same device, and should not = result > >> > in panic. Trying to implement a half-measure that only covers the pr= oblem > >> > you do a mis-service. > >> > > >> > And you still did not provided the panic message. > >> > >> I'm sorry, you're right. =9AHowever, your guess was in fact correct; > >> make_dev was being called, which returned a null pointer because it > >> failed. > >> > >> 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. > >> > >> 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? > >> > >> 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 referen= ced > > by devfs node. > > > >> Chris > >> > >> [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. >=20 > That'd be great-- but I can't work out how to do it :( >=20 > Do I need to return a different value? error =3D make_dev_p(); if (error !=3D 0) { printf("Error creating device node /dev/%s: %d\n", name, error); return (error); } Or I do not understand your question. --e/SfQGHLOMWAfGD8 Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.18 (FreeBSD) iEYEARECAAYFAk78bJMACgkQC3+MBN1Mb4jGewCg468OpxW9oKFYmDrlkfpOQ2y+ Rc0An2tDvAM3wUqfZLXP1M6zYDXFUGiD =U2gS -----END PGP SIGNATURE----- --e/SfQGHLOMWAfGD8--
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