Re: panic: Duplicate free of item 0xc5862800 from zone 0xc55f8580(NAMEI)

Someone with more time than myself should look into extending memguard
to be able to override not only malloc types but also UMA zones.  This
would help in the future with problems such as the one below (which
turned out to be a false positive), but also with real
double-frees as recently reported by JHB, for example.

-Bosko

On Sat, Mar 26, 2005 at 11:09:21PM +0000, Robert Watson wrote:
> On Sat, 26 Mar 2005, Robert Watson wrote:
> 
> > Got the following panic while doing a buildworld on a dual xeon (quad
> > logical processor) system today, using 6-CURRENT source from today.
> 
> Actually, it looks like this is a false positive -- a race introduced in
> local code because the debugging code to check for multiple frees (etc) 
> was getting called after mutexes/etc were released, so raced against
> real-world re-allocation.
> 
> Robert N M Watson
> 
> 
> > 
> > Robert N M Watson
> > 
> > Slab at 0xc5857200, freei 2 = 0.
> > panic: Duplicate free of item 0xc5862800 from zone 0xc55f8580(NAMEI)
> > 
> > cpuid = 1
> > KDB: enter: panic
> > [thread pid 10534 tid 100207 ]
> > Stopped at      kdb_enter+0x2b: nop     
> > db> trace
> > Tracing pid 10534 tid 100207 td 0xc5e27000
> > kdb_enter(c08317e5) at kdb_enter+0x2b
> > panic(c084b549,c5862800,c55f8580,c0839cfb,c084b52d) at panic+0x127
> > uma_dbg_free(c55f8580,0,c5862800) at uma_dbg_free+0x110
> > uma_zfree_arg(c55f8580,c5862800,0) at uma_zfree_arg+0xf4
> > namei(ebb3fbdc,c0626abe,c5e27000,c5e27000,c5e27000) at namei+0x245
> > vn_open_cred(ebb3fbdc,ebb3fcdc,1a4,c5ddec80,3) at vn_open_cred+0x278
> > vn_open(ebb3fbdc,ebb3fcdc,1a4,3,c0626abe) at vn_open+0x1e
> > kern_open(c5e27000,8418900,0,8001,1b6) at kern_open+0xb6
> > open(c5e27000,ebb3fd14,3,b,202) at open+0x1a
> > syscall(2f,2f,bfbf002f,0,0) at syscall+0x213
> > Xint0x80_syscall() at Xint0x80_syscall+0x1f
> > --- syscall (5, FreeBSD ELF32, open), eip = 0x82d0e27, esp = 0xbfbfe2fc,
> > ebp = 0xbfbfe318 ---
> > db> show lockedvnods
> > Locked vnodes
> > 
> > 0xc61819fc: tag ufs, type VREG
> >     usecount 1, writecount 0, refcount 4 mountedhere 0
> >     flags ()
> >     v_object 0xc6174738 ref 0 pages 5
> >      lock type ufs: EXCL (count 1) by thread 0xc5e27a10 (pid 10541)
> >         ino 2028972, on dev ar0s1e
> > 
> > 0xc6b5fd50: tag ufs, type VREG
> >     usecount 1, writecount 0, refcount 3 mountedhere 0
> >     flags ()
> >     v_object 0xc76d3528 ref 0 pages 1
> >      lock type ufs: EXCL (count 1) by thread 0xc624aa10 (pid 10538)
> >         ino 2028317, on dev ar0s1e
> > 
> > 
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-- 
Bosko Milekic
bmilekic_at_technokratis.com
bmilekic_at_FreeBSD.org