Greg Lehey wrote:
> On Monday, 28 June 1999 at 16:36:31 +0800, Peter Wemm wrote:
> > Kirk McKusick wrote:
> > [..]
> >> Greg Lehey has sent me a panic with the buffer locking in the NFS code.
> >> I am too tired to attack it tonight, but will look at it in the morning.
> >
> > I might have a look if I get a chance..
>
> I've been collecting them :-) The first one looks like this:
>
> Debugger (msg=0xc025e7fb "panic") at ../../i386/i386/db_interface.c:326
> 326 }
> #0 Debugger (msg=0xc025e7fb "panic") at ../../i386/i386/db_interface.c:326
> #1 0xc0153474 in panic (fmt=0xc02676a0 "nfs_strategy: buffer %p not locked")
at ../../kern/kern_shutdown.c:450
[..]
> It happens when I do just about any NFS write; I've been reproducing
> it with 'make depend' in the NFS-mounted kernel build directory. I'll
> try to get a dump and send you both a message about where you can find
> it.
All things being equal, this should be fixed, there was a negated assertion
in nfs_strategy. :-)
> The other one is even more simple to reproduce:
>
> $ dd if=/dev/da0d of=/dev/null bs=120b
>
> Debugger (msg=0xc025e7fb "panic") at ../../i386/i386/db_interface.c:326
> 326 }
> #0 Debugger (msg=0xc025e7fb "panic") at ../../i386/i386/db_interface.c:326
> #1 0xc0153474 in panic (fmt=0xc025d9a0 "lockmgr: locking against myself") at
../../kern/kern_shutdown.c:450
> #2 0xc014eafb in debuglockmgr (lkp=0xc2368c4c, flags=0x10022, interlkp=0xc02
c4564, p=0xc68aa3c0,
> name=0xc0261452 "lockmgr", file=0xc026145a "../../sys/buf.h", line=0x11b)
at ../../kern/kern_lock.c:341
> #3 0xc0173fc2 in getblk (vp=0xc6dcd780, blkno=0x20, size=0x2000, slpflag=0x0
, slptimeo=0x0) at ../../sys/buf.h:283
> #4 0xc0172531 in breadn (vp=0xc6dcd780, blkno=0x20, size=0x2000, rablkno=0xc
6deee44, rabsize=0xc6deee48, cnt=0x1,
> cred=0x0, bpp=0xc6deee4c) at ../../kern/vfs_bio.c:433
> #5 0xc01864d5 in spec_read (ap=0xc6deeeb4) at ../../miscfs/specfs/spec_vnops
.c:308
> #6 0xc01f8378 in ufsspec_read (ap=0xc6deeeb4) at ../../ufs/ufs/ufs_vnops.c:1
826
> #7 0xc01f8931 in ufs_vnoperatespec (ap=0xc6deeeb4) at ../../ufs/ufs/ufs_vnop
s.c:2327
> #8 0xc0180684 in vn_read (fp=0xc0f56d80, uio=0xc6deeefc, cred=0xc0f52200, fl
ags=0x0) at vnode_if.h:303
> #9 0xc015f157 in dofileread (p=0xc68aa3c0, fp=0xc0f56d80, fd=0x3, buf=0x805d
000, nbyte=0xf000,
> offset=0xffffffffffffffff, flags=0x0) at ../../kern/sys_generic.c:179
> #10 0xc015f067 in read (p=0xc68aa3c0, uap=0xc6deef80) at ../../kern/sys_gener
ic.c:111
> #11 0xc022aee6 in syscall (frame={tf_fs = 0x2f, tf_es = 0x2f, tf_ds = 0x2f, t
f_edi = 0xbfbfcfdc, tf_esi = 0xbfbfcfc8,
> tf_ebp = 0xbfbfcf90, tf_isp = 0xc6deefd4, tf_ebx = 0xbfbfcfc8, tf_edx =
0x4, tf_ecx = 0x80580a0, tf_eax = 0x3,
> tf_trapno = 0x16, tf_err = 0x2, tf_eip = 0x8049eec, tf_cs = 0x1f, tf_ef
lags = 0x246, tf_esp = 0xbfbfcf80,
> tf_ss = 0x2f}) at ../../i386/i386/trap.c:1056
> #12 0xc021c960 in Xint0x80_syscall ()
> #13 0x8048c6d in ?? ()
> #14 0x80480e9 in ?? ()
>
> For some reason, breadn() doesn't seem to work any more. It works
> find with bread(), but I haven't localized how the code differs.
Hmm...
> I've applied Kirk's patch to lockmgr, which seemed to relate to the
> breadn() problem, but it then found a different set of flags to pass
> to lockmgr (LK_SLEEPFAIL instead of LK_NOWAIT) and still cause the
> panic.
There are also some serious problems with the swap pager..
For starters, BUF_KERNPROC() internally checks that B_ASYNC is set because
that's when biodone() frees the lock. However, B_CALL may or may not free
the lock too, for example swp_pager_async_iodone() in swap_pager.c.
Also, the swap IO clustering/chainging etc is troubled since it turns on
and off B_ASYNC and does it's own freeing and waiting. I haven't got my
brain around it yet but I don't think it's going to be too hard to fix.
Incidently, I do find Matt's code and comments quite nice to work with
compared to some obscure areas.
> Greg
Cheers,
-Peter
--
Peter Wemm - [EMAIL PROTECTED]; [EMAIL PROTECTED]; [EMAIL PROTECTED]
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