Date: Tue, 18 Mar 2008 23:03:53 +0200 From: Kostik Belousov <kostikbel@gmail.com> To: Attilio Rao <attilio@freebsd.org> Cc: Alex Goncharov <alex-goncharov@comcast.net>, pluknet <pluknet@gmail.com>, freebsd-current@freebsd.org Subject: Re: Seeing lock order reversal Message-ID: <20080318210353.GE10374@deviant.kiev.zoral.com.ua> In-Reply-To: <3bbf2fe10803181216l7a1f7a5fp382b03a74d84161f@mail.gmail.com> References: <E1JbP4P-0000hU-L3@daland.home> <a31046fc0803171959n65faaf0oc9fc248ebdd8abd3@mail.gmail.com> <3bbf2fe10803181145m79e89955re785e1b5048cafd7@mail.gmail.com> <a31046fc0803181211q298da2c3v73fa8fb9f356dba9@mail.gmail.com> <3bbf2fe10803181216l7a1f7a5fp382b03a74d84161f@mail.gmail.com>
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--X/KOvfZbhhxWSrMq Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, Mar 18, 2008 at 08:16:28PM +0100, Attilio Rao wrote: > 2008/3/18, pluknet <pluknet@gmail.com>: > > On 18/03/2008, Attilio Rao <attilio@freebsd.org> wrote: > > > 2008/3/18, pluknet <pluknet@gmail.com>: > > > > > > > > > > Thought taking that into account I could obtain a new one yesterd= ay. I > > > > didn't see this before. > > > > > > > > Mar 17 03:17:14 pl sudo: pluknet : TTY=3Dttyv1 ; PWD=3D/usr/hom= e/pluknet > > > > ; USER=3Droot ; COMMAND=3D/usr/libexec/getty 3wire.9600 ttyd0 > > > > Mar 17 03:17:14 pl kernel: lock order reversal: > > > > Mar 17 03:17:14 pl kernel: 1st 0xc07e9274 proctree (proctree) @ > > > > /usr/src/sys/kern/kern_exit.c:291 > > > > Mar 17 03:17:14 pl kernel: 2nd 0xc2fc49e8 devfs (devfs) @ > > > > /usr/src/sys/kern/vfs_subr.c:2158 > > > > > > > > > This one seems interesting. > > > Next time you experience it can you please drop in DDB and print-out > > > the correct order revealed by WITNESS? > > > > > > > > > Fortunately I could reproduce it. > > > > lock order reversal: > > > > 1st 0xc07e9274 proctree (proctree) @ /usr/src/sys/kern/kern_exit.c:291 > > > > 2nd 0xc3c18278 devfs (devfs) @ /usr/src/sys/kern/vfs_subr.c:2158 > > KDB: stack backtrace: > > db_trace_self_wrapper(c07682d0,d6078b24,c0573236,c076a615,c3c18278,...) > > > > at db_trace_self_wrapper+0x26 > > > > kdb_backtrace(c076a615,c3c18278,c075bcfb,c075bcfb,c0770a8c,...) at > > kdb_backtrace+0x29 > > witness_checkorder(c3c18278,9,c0770a8c,86e,c07edcd4,...) at > > witness_checkorder+0x6d6 > > _lockmgr_args(c3c18278,20002,c3c182a8,0,ffffffff,...) at _lockmgr_args= +0x519 > > vop_stdlock(d6078bc4,d6078bbc,c0572a1c,20002,c3c182a8,...) at vop_stdl= ock+0x51 > > VOP_LOCK1_APV(c07a07e0,d6078bc4,851,d6078be4,c3c182a8,...) at VOP_LOCK= 1_APV+0xa5 > > _vn_lock(c3c18220,20002,c0770a8c,86e,4,...) at _vn_lock+0xf2 > > vrele(c3c18220,0,c07619a2,14e,ffffffff,...) at vrele+0x142 > > exit1(c2fdd690,0,d6078d2c,c0729ed3,c2fdd690,...) at exit1+0x8a1 > > sys_exit(c2fdd690,d6078cfc,4,c07625a5,c07a3d38,...) at sys_exit+0x1d > > syscall(d6078d38) at syscall+0x2b3 > > Xint0x80_syscall() at Xint0x80_syscall+0x20 > > --- syscall (1, FreeBSD ELF32, sys_exit), eip =3D 0x2811964f, esp =3D > > 0xbfbfeacc, ebp =3D 0xbfbfead8 --- > > > > Something else? >=20 > This is the "2nd order". > It would be nice to get where these locks are acquired and what is the > "1st order". > In order to get it, it is enough to break in DDB and do: show witness > at DDB prompt. >=20 > Thanks, > Attilio The other order comes from the devfs_close. Look at the handling of the controlling terminal at the start of the function. --X/KOvfZbhhxWSrMq Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.8 (FreeBSD) iEYEARECAAYFAkfgLjgACgkQC3+MBN1Mb4gtswCfbmP7MlGlOPWfD96eDY8bfsqe zXgAoMbAdvf2CL/+qpA12fHHP2fE593S =zkvW -----END PGP SIGNATURE----- --X/KOvfZbhhxWSrMq--
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