Date: Fri, 09 Jan 2009 20:23:10 -0500 From: Joe Marcus Clarke <marcus@FreeBSD.org> To: Garrett Cooper <yanefbsd@gmail.com> Cc: freebsd-current@FreeBSD.org, Richard Todd <rmtodd@ichotolot.servalan.com> Subject: Re: Recent changes to pseudofs causing panics -- leaking a vnode lock? Message-ID: <1231550590.56664.21.camel@shumai.marcuscom.com> In-Reply-To: <7d6fde3d0901091707u7e2ee080l75d8567a4093144d@mail.gmail.com> References: <20090109004853.GA34384@ichotolot.servalan.com> <1231541342.56664.19.camel@shumai.marcuscom.com> <7d6fde3d0901091707u7e2ee080l75d8567a4093144d@mail.gmail.com>
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[-- Attachment #1 --] On Fri, 2009-01-09 at 17:07 -0800, Garrett Cooper wrote: > On Fri, Jan 9, 2009 at 2:49 PM, Joe Marcus Clarke <marcus@freebsd.org> wrote: > > On Thu, 2009-01-08 at 18:48 -0600, Richard Todd wrote: > >> I've noticed that ever since updating to a kernel after the recent changes > >> to the pseudofs code late last month, that I've occasionally gotten the > >> following sort of panic: > >> > >> System call readlink returning with the following locks held: > >> exclusive lockmgr pseudofs (pseudofs) r = 0 (0xffffff00ba581cc8) locked @ /usr/src/sys/fs/pseudofs/pseudofs_vncache.c:193 > >> panic: witness_warn > >> > >> The line in question is the one I marked by an arrow in this chunk of the > >> pfs_vncache_alloc code: > >> if ((pn->pn_flags & PFS_PROCDEP) != 0) > >> (*vpp)->v_vflag |= VV_PROCDEP; > >> pvd->pvd_vnode = *vpp; > >> VN_LOCK_AREC(*vpp); > >> vn_lock(*vpp, LK_EXCLUSIVE | LK_RETRY); <==== this lock here > >> error = insmntque(*vpp, mp); > >> > >> So somehow, a vnode is getting locked here and not getting unlocked. > >> I suspect the code in the retry2: loop later, simply because that's > >> the code that got added in the late December commits, but I'm not > >> clear on how exactly. I've tried littering the code with extra > >> printfs to try to clarify what's going on, but alas, I'm still not > >> really sure what's going on. I do have a good coredump that I can get > >> info out of, if someone can suggest to me what would be useful things > >> to dump. Anyway, here's the patch for the debugging printfs I added, > >> and the console messages produced by those printfs from the most > >> recent coredump/panic. The console msgs do seem to indicate some sort > >> of race condition going on, though, as they seem to show two or more processes > >> simultaneously hitting the pseudofs code and hitting my debugging print > >> statements (alas, making the console log rather a confused mess.) > > > > I believe I have fixed this in HEAD. Kib gave his review and approval, > > and the fix really should prevent this hang. Please report back if you > > still see the problem. > > > > Joe > > Joe, > When did you do this commit / what's the SVN revision #? $FreeBSD: head/sys/fs/pseudofs/pseudofs_vncache.c 186981 2009-01-09 22:06:48Z marcus $ Joe -- Joe Marcus Clarke FreeBSD GNOME Team :: gnome@FreeBSD.org FreeNode / #freebsd-gnome http://www.FreeBSD.org/gnome [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (FreeBSD) iEYEABECAAYFAkln+H0ACgkQb2iPiv4Uz4c3WgCgjKUq+jrxwm2JwAJLyRKqft02 K4wAoJh0N3Z4GFSYzTP0hQ8VpMyADYvy =S1zJ -----END PGP SIGNATURE-----help
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