From owner-freebsd-hackers  Mon Dec 17 13:31:22 2001
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Date: Mon, 17 Dec 2001 22:35:36 +0100 (CET)
From: Martin Blapp <mb@imp.ch>
To: Matthew Dillon <dillon@apollo.backplane.com>
Cc: <freebsd-hackers@FreeBSD.ORG>
Subject: Re: deadlock with softupdates ?
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Hi Matt,

>     Yahoo noticed a deadlock in the vnode recycling code.  If your machine
>     below is hitting the kern.maxvnodes limit it could be the same thing.
>     The way to tell is to generate a kernel core along with the debug
>     version of the kernel binary (/usr/src/sys/compile/<KERNEL>/kernel.debug),
>     and backtrace each locked-up process to see if any of them are going
>     through the recycle code.

It cannot be kern.maxvnodes, cause the newsserver is using the cyclic
news filesystem. And there is also enough ram.

It seems to be a vnode deadlock:

(kgdb) defproc 2
    2 d78cd0c0 d6445000    0     0     0  100204 3  pagedaemon   inode c2c0c200
 frame 0 at 0xd6447e24: ebp d6447e50, eip 0xc017a529 <tsleep+417>:      mov    0x141(%ebx),%al
 frame 1 at 0xd6447e50: ebp d6447e74, eip 0xc0171c24 <acquire+140>:     mov    %eax,%esi
 frame 2 at 0xd6447e74: ebp d6447e98, eip 0xc0171ea5 <lockmgr+581>:     mov    %eax,%edi
 frame 3 at 0xd6447e98: ebp d6447eb0, eip 0xc01a2008 <vop_stdunlock+12>:       jmp    0xc01a200e <vop_stdunlo>
 frame 4 at 0xd6447eb0: ebp d6447ebc, eip 0xc022e44d <default_pager_alloc+1>:   leave
 frame 5 at 0xd6447ebc: ebp d6447ee4, eip 0xc01ac04b <vn_lock+155>:     add    $0x4,%esp
 frame 6 at 0xd6447ee4: ebp d6447f00, eip 0xc01a4e18 <vget+148>:        mov    %eax,%esi
 frame 7 at 0xd6447f00: ebp d6447f84, eip 0xc023a52d <vm_pageout_scan+873>:     add    $0xc,%esp
 frame 8 at 0xd6447f84: ebp d6447f9c, eip 0xc023af53 <pagedaemon_wakeup+31>:    movl   $0x0,0xc02eff1c

(kgdb) x/x 0xd6447f00
0xd6447f00:     0xd6447f84
(kgdb) x/10 0xd6447f00
0xd6447f00:     0xd6447f84      0xc023a52d      0xd7e5a180      0x00040002
0xd6447f10:     0xd47c2c60      0x00000000      0x00000000      0x00000000
0xd6447f20:     0xd7e5a180      0x00000020
(kgdb) showcache 0xd7e5a180
history.hash

Can you help me to debug this bug ?

Martin


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