Re: lock order reversal

On Mon, 26 Feb 2018 08:42:14 +0200 "Andriy Gapon" <avg_at_FreeBSD.org> said

> On 26/02/2018 07:18, Jon Brawn wrote:
> > Wotcha!
> > 
> > So, I’ve been using FreeBSD 12-CURRENT at various svn releases for a while
> > now, and I get quite a few “lock order reversal” dumps. The one I’ve got
> > on my screen at the moment is for ufs / bufwait / ufs:
> > 
> > root_at_brax:/usr/src/stand # lock order reversal:
> >  1st 0xfffffd0003ec17e8 ufs (ufs) _at_ /usr/src/sys/kern/vfs_subr.c:2602
> >  2nd 0xffff0000410efa20 bufwait (bufwait) _at_
> >  /usr/src/sys/ufs/ffs/ffs_vnops.c:282
> >  3rd 0xfffffd00b83ca7e8 ufs (ufs) _at_ /usr/src/sys/kern/vfs_subr.c:2602
> > stack backtrace:
> > #0 0xffff0000003b59d4 at witness_debugger+0x64
> > #1 0xffff00000032bd34 at __lockmgr_args+0x6ac
> > #2 0xffff0000005c6af0 at ffs_lock+0x88
> > #3 0xffff000000679eb0 at VOP_LOCK1_APV+0xac
> > #4 0xffff000000426fa8 at _vn_lock+0x64
> > #5 0xffff000000417550 at vget+0x78
> > #6 0xffff000000409fdc at vfs_hash_get+0xec
> > #7 0xffff0000005c2b94 at ffs_vgetf+0x44
> > #8 0xffff0000005b96a8 at softdep_sync_buf+0x9f4
> > #9 0xffff0000005c7834 at ffs_syncvnode+0x26c
> > #10 0xffff0000005a1b5c at ffs_truncate+0x6b0
> > #11 0xffff0000005ce3cc at ufs_direnter+0x778
> > #12 0xffff0000005d64bc at ufs_makeinode+0x4b8
> > #13 0xffff0000005d2b90 at ufs_create+0x38
> > #14 0xffff000000677168 at VOP_CREATE_APV+0xac
> > #15 0xffff00000042691c at vn_open_cred+0x264
> > #16 0xffff00000041fc84 at kern_openat+0x208
> > #17 0xffff00000064b59c at do_el0_sync+0x8bc
> > 
> > Is there something I should be doing to help debug these?
> 
> IMO, no. Please ignore LORs involving "bufwait", "filedesc structure",
> "syncer"
> unless you experience any real problem (like a lock up).
Or build a kernel without WITNESS (and FULL_BUF_TRACKING?) :-)

--Chris
> 
> -- 
> Andriy Gapon
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