Re: contemporary -current panic: locking against myself

From: Dmitry Morozovsky <marck_at_rinet.ru>
Date: Fri, 3 Aug 2007 16:49:30 +0400 (MSD)
On Fri, 3 Aug 2007, Pawel Jakub Dawidek wrote:

PJD> > FreeBSD/i386 on Athlon X2, HEAD without WITNESS. 4G of RAM. tmpfs used for 
PJD> > 'make release'.
PJD> > 
PJD> > 
PJD> > panic: lockmgr: locking against myself
PJD> > cpuid = 0
PJD> > KDB: enter: panic
PJD> > [thread pid 19396 tid 100245 ]
PJD> > Stopped at      kdb_enter+0x32: leave
PJD> > 
PJD> > db> tr  
PJD> > Tracing pid 19396 tid 100245 td 0xce194220
PJD> > kdb_enter(c066f664,0,c066dca9,e92799cc,0,...) at kdb_enter+0x32
PJD> > panic(c066dca9,e92799dc,c0559cc7,e9279ac0,ca2f7770,...) at panic+0x124
PJD> > _lockmgr(ca2f77c8,3002,ca2f77f8,ce194220,c0675afc,...) at _lockmgr+0x401
PJD> > vop_stdlock(e9279a5c,ce194220,3002,ca2f7770,e9279a80,...) at vop_stdlock+0x40
PJD> > VOP_LOCK1_APV(d06417e0,e9279a5c,e9279bc0,0,c8d00330,...) at VOP_LOCK1_APV+0x46
PJD> > _vn_lock(ca2f7770,3002,ce194220,c0675afc,7f3,...) at _vn_lock+0x166
PJD> > vget(ca2f7770,1000,ce194220,0,e9279b98,...) at vget+0x114
PJD> > vm_object_reference(d1c70348,e9279b30,c063f81d,c0c71000,e381d000,...) at 
PJD> > vm_object_reference+0x12a
PJD> > kern_execve(ce194220,e9279c5c,0,28204548,282045d8,e381d000,e381d000,e381d015,e381d4dc,e385d000,3fb24,3,20) 
PJD> > at kern_execve+0x31a
PJD> > execve(ce194220,e9279cfc,c,ce194220,e9279d2c,...) at execve+0x4c
PJD> > syscall(e9279d38) at syscall+0x345
PJD> > Xint0x80_syscall() at Xint0x80_syscall+0x20
PJD> > --- syscall (59, FreeBSD ELF32, execve), eip = 0x28146a47, esp = 0xbfbfe4cc, 
PJD> > ebp = 0xbfbfe4e8 ---
PJD> > 
PJD> > db> show lockedvnods
PJD> > Locked vnodes
PJD> > 
PJD> > 0xca2f7770: tag tmpfs, type VREG
PJD> >     usecount 1, writecount 0, refcount 4 mountedhere 0
PJD> >     flags ()
PJD> >     v_object 0xd1c70348 ref 1 pages 19
PJD> >      lock type tmpfs: EXCL (count 1) by thread 0xce194220 (pid 19396) with 1 
PJD> > pending
PJD> > tag VT_TMPFS, tmpfs_node 0xd177f9d4, flags 0x0, links 9
PJD> >         mode 0555, owner 0, group 0, size 76648, status 0x0
PJD> > 
PJD> > It seems there is some locking problem in tmpfs.
PJD> > 
PJD> > What other info should I provide to help resolve the problem?
PJD> 
PJD> Here you can find two patches, which may or may not fix your problem.
PJD> The first one is actually only to improve debug.
PJD> 
PJD> This patch adds all vnode flags to the output, because I believe you
PJD> have VI_OWEINACT set, but not printed:
PJD> 
PJD> 	http://people.freebsd.org/~pjd/patches/vfs_subr.c.4.patch
PJD> 
PJD> The problem here is that vm_object_reference() calls vget() without any
PJD> lock flag and vget() locks vnode exclusively when the VI_OWEINACT flag
PJD> is set. vget() should probably be fixed too, but jeff_at_ opinion is that
PJD> it shouldn't happen in this case, so this may be tmpfs bug.
PJD> 
PJD> The patch below fixes some locking problems in tmpfs:
PJD> 
PJD> 	http://people.freebsd.org/~pjd/patches/tmpfs.patch
PJD> 
PJD> The problems are:
PJD> - tmpfs_root() should honour 'flags' argument, and not always lock the
PJD>   vnode exclusively,
PJD> - tmpfs_lookup() should lock vnode using cnp->cn_lkflags, and not always
PJD>   do it exclusively,
PJD> - in ".." case when we unlock directory vnode to avoid deadlock, we
PJD>   should relock it using the same type of lock it was locked before and
PJD>   not always relock it exclusively,
PJD> 
PJD> Note, that this patch wasn't even compiled tested.

Well, it at least compiled and booted on i386. Test release run is in progress 
now, i'll followup with the results.

Sincerely,
D.Marck                                     [DM5020, MCK-RIPE, DM3-RIPN]
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*** Dmitry Morozovsky --- D.Marck --- Wild Woozle --- marck_at_rinet.ru ***
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Received on Fri Aug 03 2007 - 10:49:33 UTC

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