Date: Tue, 12 Jun 2012 01:53:04 +0300 From: Konstantin Belousov <kostikbel@gmail.com> To: Steven Haber <steven.haber@isilon.com> Cc: freebsd-geom@freebsd.org Subject: Re: Geom / destroy_dev() deadlock Message-ID: <20120611225304.GK2337@deviant.kiev.zoral.com.ua> In-Reply-To: <56CE86D6660FF84498426FA7A33170B403429115@seaxch01.desktop.isilon.com> References: <56CE86D6660FF84498426FA7A33170B4033672EF@seaxch01.desktop.isilon.com> <20120611204334.GH2337@deviant.kiev.zoral.com.ua> <56CE86D6660FF84498426FA7A33170B403367535@seaxch01.desktop.isilon.com> <20120611215610.GJ2337@deviant.kiev.zoral.com.ua> <56CE86D6660FF84498426FA7A33170B403429115@seaxch01.desktop.isilon.com>
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--EMQjp+MvU6EBGjHc Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Jun 11, 2012 at 03:27:39PM -0700, Steven Haber wrote: > > I do not understand what you are proposing. Could you, please, show > > the patch ? >=20 > --- > src/sys/geom/geom_dev.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) >=20 > diff --git a/src/sys/geom/geom_dev.c b/src/sys/geom/geom_dev.c > index 38251e1..787235a 100644 > --- a/src/sys/geom/geom_dev.c > +++ b/src/sys/geom/geom_dev.c > @@ -497,7 +497,7 @@ g_dev_orphan(struct g_consumer *cp) > =20 > /* Destroy the struct cdev *so we get no more requests */ > unit =3D dev2unit(dev); > - destroy_dev(dev); > + destroy_dev_sched(dev); > free_unr(unithdr, unit); > =20 > /* Wait for the cows to come home */ Did you noted the comment above the block you changing ? The patch would cause races allowing arbitrary kernel memory corruption. The moment when the cdev is destroyed is somewhere in future, while structures that the cdev reference are freed synchronously. I tried to put some safety measures into destroy_dev_sched(9), namely CDP_SCHED_DTR flag that somewhat reduces the possibility of usermode accessing cdev after destroy_dev_sched(), but this cannot be eliminated entirely. --EMQjp+MvU6EBGjHc Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (FreeBSD) iEYEARECAAYFAk/WdtAACgkQC3+MBN1Mb4jpDQCgiBoVnAOan9YOILDSohRzV8HC uFIAn1QA/tyJRtL/xtZm7chlsJtltTcE =8EDz -----END PGP SIGNATURE----- --EMQjp+MvU6EBGjHc--
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