Re: SMP FFS Part 3

On Fri, 3 Dec 2004, Jeff Roberson wrote:

> This patch removes Giant from every file related syscall.  It fixes all
> known bugs except for one which Peter Holm has seen after very long
> periods of extreme load, and a nfs netbooting problem that I haven't yet
> looked in to.  I can buildworld -j3 for hours on my dual opteron without
> issues.  I hope to fix the remaining problems in a day or two. 
> 
> http://www.chesapeake.net/~jroberson/smpffs.diff

In installed the latest patch on a box a couple of minutes ago, and began
a second update of a CVS tree over NFS to an NFS-mounted directory, got
this: 

hippy# cvs -q update -dP
panic: lock (sleep mutex) Giant not locked _at_ kern/vfs_lookup.c:220
cpuid = 0
KDB: enter: panic
[thread pid 1117 tid 100168 ]
Stopped at      kdb_enter+0x2c: leave   
db> bt
No such command
db> trace
Tracing pid 1117 tid 100168 td 0xc2b23c00
kdb_enter(c081ddbe,100,c2b23c00,c2b23c70,c08de5a0) at kdb_enter+0x2c
panic(c0821748,c0835631,c082e79d,c0825f81,dc) at panic+0x17f
witness_unlock(c08de5a0,8,c0825f78,dc) at witness_unlock+0x170
_mtx_unlock_flags(c08de5a0,0,c0825f78,dc) at _mtx_unlock_flags+0x3b
namei(ef1ffc30,80c2000,1000000,0,c2731bdc) at namei+0x5f0
stat(c2b23c00,ef1ffd14,2,1,212) at stat+0x4a
syscall(2f,2f,2f,80c40dc,80c1402) at syscall+0x128
Xint0x80_syscall() at Xint0x80_syscall+0x1f
--- syscall (188, FreeBSD ELF32, stat), eip = 0x282d8747, esp =
0xbfbfe8cc, ebp = 0xbfbfeb78 ---
db> show locks
db> show pcpu
cpuid        = 0
curthread    = 0xc2b23c00: pid 1117 "cvs"
curpcb       = 0xef1ffda0
fpcurthread  = none
idlethread   = 0xc2281a80: pid 14 "idle: cpu0"
APIC ID      = 0
currentldt   = 0x30
spin locks held:

The first update of the same tree didn't cause a problem, so maybe it's a
path we hit the second time due to cached lookups/etc?

Robert N M Watson             FreeBSD Core Team, TrustedBSD Projects
robert_at_fledge.watson.org      Principal Research Scientist, McAfee Research