Date: Mon, 22 Jan 2007 16:36:48 +0100 From: "Attilio Rao" <attilio@freebsd.org> To: "Kostik Belousov" <kostikbel@gmail.com> Cc: bzeeb-lists@lists.zabbadoz.net, src-committers@freebsd.org, cvs-all@freebsd.org, cvs-src@freebsd.org Subject: Re: cvs commit: src/sys/fs/deadfs dead_vnops.c src/sys/kern vfs_lookup.c Message-ID: <3bbf2fe10701220736l729c2915v58f25cc1908d923a@mail.gmail.com> In-Reply-To: <20070122122509.GB71333@deviant.kiev.zoral.com.ua> References: <200701221125.l0MBPMS4041567@repoman.freebsd.org> <20070122115230.J82671@maildrop.int.zabbadoz.net> <20070122122509.GB71333@deviant.kiev.zoral.com.ua>
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2007/1/22, Kostik Belousov <kostikbel@gmail.com>: > On Mon, Jan 22, 2007 at 11:53:50AM +0000, Bjoern A. Zeeb wrote: > > On Mon, 22 Jan 2007, Konstantin Belousov wrote: > > > > >kib 2007-01-22 11:25:22 UTC > > > > > > FreeBSD src repository > > > > > > Modified files: > > > sys/fs/deadfs dead_vnops.c > > > sys/kern vfs_lookup.c > > > Log: > > > Below is slightly edited description of the LOR by Tor Egge: > > > > > > -------------------------- > > > [Deadlock] is caused by a lock order reversal in vfs_lookup(), where > > > [some] process is trying to lock a directory vnode, that is the parent > > > directory of covered vnode) while holding an exclusive vnode lock on > > > covering vnode. > > >.... > > > To fix the LOR, ups@ noted that when crossing the mount point, ni_dvp > > > is actually not used by the callers of namei. Thus, placeholder deadfs > > > vnode vp_crossmp is introduced that is filled into ni_dvp. > > > > which of the LOR #s on "The LOR page" can be marked "patched" with > > this commit? > > > > http://sources.zabbadoz.net/freebsd/lor.html > > None, your page lists only LORs that are detectable by WITNESS. This one is > between lockmgr lock and vfs_busy(), both of them are invisible to WITNESS. FYI, I tried to add WITNESS support to lockmgr but kernel hangs on a vfs lockmgr. This is a very strange bug and it suggests their implementation is very fragile (from this the necessity to rewrite them: //depot/user/attilio/attilio_lockmgr/... on perforce). -- Peace can only be achieved by understanding - A. Einstein
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