Subject: kern/12183: uvm hangs on a process, then takes out the system
To: None <gnats-bugs@gnats.netbsd.org>
From: John Hawkinson <jhawk@mit.edu>
List: netbsd-bugs
Date: 02/11/2001 06:54:31
>Number:         12183
>Category:       kern
>Synopsis:       uvm hangs on a process, then takes out the system
>Confidential:   no
>Severity:       serious
>Priority:       low
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Feb 11 06:57:00 PST 2001
>Closed-Date:
>Last-Modified:
>Originator:     John Hawkinson
>Release:        -current of 7 Feb 2000
>Organization:
MIT
>Environment:
	
System: NetBSD zorkmid.mit.edu 1.5R NetBSD 1.5R (ZORKMID-$Revision: 1.6 $) #89: Wed Feb 7 23:37:46 EST 2001 jhawk@zorkmid.mit.edu:/usr/local/netbsd-current/src/sys/arch/i386/compile/ZORKMID i386


>Description:
	While building a library in the bowels of bsd.lib.mk, an "nm -go"
process got stuck. It ran for 10 minutes before I noticed it (it should
have been nigh instantaneous), and was swapped out.

	Investigation showed it was tsleeping at uvn_fp2. I began
some investigation with mycroft's assistance and basically got as far
as obtaining a stack trace, displaying the page it was blocked on (from the
WCHAN data), and getting a ps of some other processes, before going to sleep.

	After waking up, chs and I started to look at it, but the story had
changed due to nightly cron jobs running (a find was stuck in vnlock),
and shortly afterwards the system pseudohung[*], and I was unable to get
more work done.

	This is not trivially reproducible (suck). Various data follow.

[*] pseudohung: I tried to start emacs an emacs and it hung forever,
and I switched out of X to ddb to look at things, and then switched
back, and X was hung. Mouse would not move. The machine still pinged.
It would accept connections, but not send data over them, except for
inetd internal servicers (chargen and echo were the two I tried).
"finger", for instance, would hang. I gave up and rebooted the machine
the hard way.

Thanks to Charles and Chuq for their assistance.


>How-To-Repeat:
	
02:42am: ps listing from ddb:
db>  PID          COMMAND     EMUL  PRI UTIME STIME WAIT-MSG    WAIT-CHANNEL
 4659              nm   netbsd    4   0.0   0.0 uvn_fp2     0xc073eab0
 4656           tsort   netbsd   24   0.0   0.0 netio       0xc086b944
 4655              sh   netbsd   32   0.0   0.0 wait        0xc6eb13ac
 4654              sh   netbsd   32   0.0   0.0 wait        0xc6eb1acc
 4653              sh   netbsd   24   0.0   0.0 netio       0xc086bd1c
 4353            make   netbsd   32   0.0   0.0 wait        0xc6eb101c
 4352              sh   netbsd   32   0.0   0.0 wait        0xc6eb11e4
 4323            make   netbsd   32   0.0   0.0 wait        0xc6eb1c94
 4172            less   netbsd   50   0.0   0.0
 3943             ssh   netbsd   24   1.4   1.8 select      selwait
 3941        dhclient   netbsd   24   0.0   0.0 select      selwait
 3767             ssh   netbsd   24   0.1   0.0 netio       0xc08d43ac
 3766            less   netbsd   50   0.0   0.0
 3765             cvs   netbsd   24   0.0   0.0 netio       0xc08d4828
 3760             ssh   netbsd   24   0.0   0.0
 3759            less   netbsd   50   0.0   0.0
 3758             cvs   netbsd   24   0.0   0.0 netio       0xc086b77c
 3744            tcsh   netbsd   50   0.0   0.0
 3705              vi   netbsd   50   0.0   0.0
 2670        netscape    linux   24   0.0   0.0 select      selwait
 2669        netscape    linux   24 230.8  47.8 select      selwait

Attempts to get a trace of pid 4659 fail bascuae it's swapped out.
!wakeup()ing the wait channel succeeds. Stack trace:

db> trace: pid 4659 at 0xc6f02b1c
bpendtsleep(c073eab0,204,c045b0e4,0,c6d7c038) at bpendtsleep
uvn_findpage(c6d7c038,0,0,c6f02ca4,0) at uvn_findpage+0x47
uvn_findpages(c6d7c038,0,0,c6f02c98,c6f02ca4,0) at uvn_findpages+0x40
genfs_getpages(c6f02cfc,c6d7c038,c6f02dc8,0,c0439fc0) at genfs_getpages+0x462
VOP_GETPAGES(c6d7c038,0,0,c6f02d64,c6f02dbc) at VOP_GETPAGES+0x58
ufs_balloc_range(c6d7c038,13f,0,1ec1,0) at ufs_balloc_range+0x188
ffs_write(c6f02e80,1,c04396a0,c6d7c038,c6f02f0c) at ffs_write+0x1fd
VOP_WRITE(c6d7c038,c6f02f0c,1,c0871d00,c6d7c038) at VOP_WRITE+0x38
vn_write(c6c64190,c6c641ac,c6f02f0c,c0871d00,1) at vn_write+0x9e
dofilewrite(c6ef41f0,1,c6c64190,8057000,2000) at dofilewrite+0x94
sys_write(c6ef41f0,c6f02f88,c6f02f80) at sys_write+0x67
syscall_plain(1f,1f,8057000,804cd38,bfbfd0c0) at syscall_plain+0x98

2:52am ps:

db>  PID          COMMAND     EMUL  PRI UTIME STIME WAIT-MSG    WAIT-CHANNEL
 4792            less   netbsd   25   0.0   0.0 ttyin       0xc63f47cc
 4785            less   netbsd   50   0.0   0.0
 4780            less   netbsd   50   0.0   0.0
 4775            tcsh   netbsd   40   0.0   0.0 pause       0xc6eba984
 4774           xterm   netbsd   24   0.1   0.0 select      selwait
 4772            more   netbsd   50   0.0   0.0
 4771              sh   netbsd   32   0.0   0.0
 4770             man   netbsd   32   0.0   0.0
 4769            less   netbsd   25   0.0   0.0 ttyin       0xc63f46b0
 4767            less   netbsd   50   0.1   0.0
 4766         objdump   netbsd   24   0.0   0.0 netio       0xc08d41c0
 4723            less   netbsd   50   0.0   0.0
 4659              nm   netbsd    4   0.0   0.0 uvn_fp2     0xc073eab0
 4656           tsort   netbsd   24   0.0   0.0 netio       0xc086b944
 4655              sh   netbsd   32   0.0   0.0 wait        0xc6eb13ac
 4654              sh   netbsd   32   0.0   0.0 wait        0xc6eb1acc
 4653              sh   netbsd   24   0.0   0.0 netio       0xc086bd1c
 4353            make   netbsd   32   0.0   0.0 wait        0xc6eb101c
 4352              sh   netbsd   32   0.0   0.0 wait        0xc6eb11e4
 4323            make   netbsd   32   0.0   0.0 wait        0xc6eb1c94
 4172            less   netbsd   50   0.0   0.0

2:58am ps:
db>  PID          COMMAND     EMUL  PRI UTIME STIME WAIT-MSG    WAIT-CHANNEL
 4794            less   netbsd   50   0.0   0.0
 4792            less   netbsd   50   0.0   0.0
 4785            less   netbsd   50   0.0   0.0
 4780            less   netbsd   25   0.0   0.0 ttyin       0xc63f47cc
 4775            tcsh   netbsd   40   0.0   0.0 pause       0xc6eba984
 4774           xterm   netbsd   24   0.2   0.0 select      selwait
 4769            less   netbsd   25   0.0   0.0 ttyin       0xc63f46b0
 4767            less   netbsd   50   0.1   0.0
 4766         objdump   netbsd   24   0.0   0.0 netio       0xc08d41c0
 4723            less   netbsd   50   0.0   0.0
 4659              nm   netbsd    4   0.0   0.0 uvn_fp2     0xc073eab0
 4656           tsort   netbsd   24   0.0   0.0 netio       0xc086b944
 4655              sh   netbsd   32   0.0   0.0 wait        0xc6eb13ac
 4654              sh   netbsd   32   0.0   0.0 wait        0xc6eb1acc
 4653              sh   netbsd   24   0.0   0.0 netio       0xc086bd1c
 4353            make   netbsd   32   0.0   0.0 wait        0xc6eb101c
 4352              sh   netbsd   32   0.0   0.0 wait        0xc6eb11e4
 4323            make   netbsd   32   0.0   0.0 wait        0xc6eb1c94
 4172            less   netbsd   50   0.0   0.0
 3943             ssh   netbsd   24   1.4   1.8 select      selwait
 3941        dhclient   netbsd   24   0.0   0.0 select      selwait

'show page' of the wait channel:

db> PAGE 0xc073eab0:
  flags=7<BUSY,WANTED,TABLED>, pqflags=4<ACTIVE>, vers=46, wire_count=0, pa=0x3543000
  uobject=0xc6d7c038, uanon=0x0, offset=0x0 loan_count=0
  [page ownership tracking disabled]

Another ps listing, 3:09am:

db>  PID          COMMAND     EMUL  PRI UTIME STIME WAIT-MSG    WAIT-CHANNEL
 4818            less   netbsd   50   0.0   0.0
 4802            less   netbsd   50   0.0   0.0
 4794            less   netbsd   50   0.0   0.0
 4792            less   netbsd   50   0.0   0.0
 4785            less   netbsd   50   0.0   0.0
 4780            less   netbsd   50   0.0   0.0
 4775            tcsh   netbsd   25   0.0   0.0 ttyin       0xc63f47cc
 4774           xterm   netbsd   24   0.4   0.1 select      selwait
 4769            less   netbsd   25   0.0   0.0 ttyin       0xc63f46b0
 4767            less   netbsd   50   0.1   0.0
 4766         objdump   netbsd   24   0.0   0.0 netio       0xc08d41c0
 4723            less   netbsd   50   0.0   0.0
 4659              nm   netbsd    4   0.0   0.0 uvn_fp2     0xc073eab0
 4656           tsort   netbsd   24   0.0   0.0 netio       0xc086b944
 4655              sh   netbsd   32   0.0   0.0 wait        0xc6eb13ac
 4654              sh   netbsd   32   0.0   0.0 wait        0xc6eb1acc
 4653              sh   netbsd   24   0.0   0.0 netio       0xc086bd1c
 4353            make   netbsd   32   0.0   0.0 wait        0xc6eb101c
 4352              sh   netbsd   32   0.0   0.0 wait        0xc6eb11e4
 4323            make   netbsd   32   0.0   0.0 wait        0xc6eb1c94
 4172            less   netbsd   50   0.0   0.0
 3943             ssh   netbsd   24   1.4   1.8 select      selwait
 3941        dhclient   netbsd   24   0.0   0.0 select      selwait
 3767             ssh   netbsd   24   0.1   0.0 netio       0xc08d43ac
 3766            less   netbsd   50   0.0   0.0
 3765             cvs   netbsd   24   0.0   0.0 netio       0xc08d4828
 3760             ssh   netbsd   24   0.0   0.0
 3759            less   netbsd   50   0.0   0.0
 3758             cvs   netbsd   24   0.0   0.0 netio       0xc086b77c
 3744            tcsh   netbsd   50   0.0   0.0
 3705              vi   netbsd   50   0.0   0.0
 2670        netscape    linux   24   0.0   0.0 select      selwait
 2669        netscape    linux   24 233.6  48.1 select      selwait
 1523           sshd1   netbsd   24   1.9   0.0 select      selwait
 398             tcsh   netbsd   40   0.2   0.1 pause       0xc6e75c84
 397            xterm   netbsd   24   5.6   2.5 select      selwait
 374              zhm   netbsd   24   0.0   0.2 select      selwait
 351             tcsh   netbsd   50   0.0   0.0
 334             tcsh   netbsd   40   0.0   0.0 pause       0xc6e75014
 333             tcsh   netbsd   40   0.0   0.0 pause       0xc6e5cc80
 332             tcsh   netbsd   25   0.0   0.2 ttyin       0xc63f4478
 331            xterm   netbsd   24   6.8   2.8 select      selwait
 330            xterm   netbsd   24   2.4   1.4 select      selwait
 329         xconsole   netbsd   24   0.0   0.0 select      selwait
 328           xclock   netbsd   24   0.1   0.1 select      selwait
 327              twm   netbsd   24   1.5   1.4 select      selwait
 321            xterm   netbsd   24   4.2   2.5 select      selwait
 318        XF86_SVGA   netbsd   24 216.2  36.5 select      selwait
 317            xinit   netbsd   32   0.0   0.0 wait        0xc6dfd008
 316               sh   netbsd   32   0.0   0.0 wait        0xc6c55c7c
 314        ssh-agent   netbsd   24   1.6   0.0 select      selwait
 220            getty   netbsd   25   0.0   0.0 ttyopn      0xc63f4008
 219            getty   netbsd   25   0.0   0.0 ttyin       0xc6d778f0
 218            getty   netbsd   25   0.0   0.0 ttyin       0xc6d777d4
 217             tcsh   netbsd   25   0.0   0.0 ttyin       0xc6d776b8
 216             tcsh   netbsd   40   0.0   0.0 pause       0xc6c3a31c
 214             cron   netbsd   32   0.0   0.4 nanosleep   nanowait.110
 210            inetd   netbsd   24   0.0   0.0 select      selwait
 185             apmd   netbsd   24   0.0   3.4 select      selwait
 114          rpcbind   netbsd   24   0.0   0.0 select      selwait
 110            named   netbsd   24   1.0   0.4 select      selwait
 102          syslogd   netbsd   24   0.0   0.4 select      selwait
 8           aiodoned   netbsd    4   0.0   0.2 aiodoned    uvm+0x54
 7            ioflush   netbsd   40   0.0  32.4 syncer      rushjob
 6             reaper   netbsd    4   0.0   0.1 reaper      deadproc
 5         pagedaemon   netbsd    4   0.0   0.5 pgdaemon    uvm+0x48
 4               apm0   netbsd   32   0.053305.5 apmev       0xc07c6400
 3          cardslot0   netbsd   32   0.0   3.1 cardslotev  0xc07b3344
 2               usb0   netbsd   32   0.0   0.0 usbevt      0xc07b38c0
 1               init   netbsd   32   0.0   0.0 wait        0xc6c36000
 0            swapper   netbsd    4   0.0   0.1 scheduler   proc0
db> 

A pair of ps listings from 9:02am. Notice that find is stuck in vnlock:

db>  PID             PPID       PGRP        UID S   FLAGS          COMMAND    WAIT
 4893            4886       4885          0 3  0x4004             find  vnlock
 4888            4885       4885          0 3  0x4184         sendmail   netio
 4887            4885       4885          0 3  0x4084              tee   netio
 4886            4885       4885          0 3  0x4084               sh    wait
 4885            4884       4885          0 3  0x4084               sh    wait
 4884             214        214          0 3    0x84             cron   netio
 4818            4775       4818      10786 4  0x5002             less        
 4802            4775       4802      10786 4  0x5002             less        
 4794            4775       4794      10786 4  0x5002             less        
 4792            4775       4792      10786 4  0x5002             less        
 4785            4775       4785      10786 4  0x5002             less        
 4780            4775       4780      10786 4  0x5002             less        
 4775            4774       4775      10786 3  0x4086             tcsh   ttyin
 4774               1        321      10786 3  0x4186            xterm  select
 4769             398       4769      10786 3  0x5082             less   ttyin
 4767             398       4766      10786 4  0x5002             less        
 4766             398       4766      10786 4  0x5082          objdump   netio
 4723             332       4722      10786 4  0x5002             less        
 4659               1       4323      10786 3  0x4002               nm uvn_fp2
 4656            4654       4323      10786 3  0x4082            tsort   netio
 4655            4654       4323      10786 3  0x4082               sh    wait
 4654            4653       4323      10786 3    0x82               sh    wait
 4653            4353       4323      10786 3  0x4082               sh   netio
 4353            4352       4323      10786 3  0x4082             make    wait
 4352            4323       4323      10786 3  0x4082               sh    wait
 4323             334       4323      10786 3  0x5082             make    wait
 4172             334       4171      10786 4  0x5002             less        
 3943             333       3943      10786 3  0x4186              ssh  select
 3941               1       3941          0 3    0x84         dhclient  select
 3767            3765       3765      10786 4  0x4182              ssh   netio
 3766             398       3765      10786 4  0x5002             less        
 3765             398       3765      10786 4  0x5082              cvs   netio
 3760            3758       3758      10786 4  0x4182              ssh        
 3759             398       3758      10786 4  0x5002             less        
 3758             398       3758      10786 4  0x5082              cvs   netio
 3744             398       3744          0 4  0x5002             tcsh        
 3705             398       3705      10786 4  0x5002               vi        
 2670            2669       2669      10786 3  0x4082         netscape  select
 2669             332       2669      10786 3  0x4086         netscape  select
 1523               1       1523          0 3    0x84            sshd1  select
 398              397        398      10786 3  0x4082             tcsh   pause
 397                1        321      10786 3  0x4182            xterm  select
 374                1        374      10786 3    0x80              zhm  select
 351              332        351          0 4  0x5002             tcsh        
 334              331        334      10786 3  0x4082             tcsh   pause
 333              321        333      10786 3  0x4082             tcsh   pause
 332              330        332      10786 3  0x4082             tcsh   ttyin
 331              321        321      10786 3  0x4186            xterm  select
 330              321        321      10786 3  0x4182            xterm  select
 329              321        321      10786 3  0x4082         xconsole  select
 328              321        321      10786 3  0x4086           xclock  select
 327              321        321      10786 3  0x4086              twm  select
 321              317        321      10786 3  0x4186            xterm  select
 318              317        318      10786 3  0x4184        XF86_SVGA  select
 317              316        316      10786 3  0x4082            xinit    wait
 316              216        316      10786 3  0x5082               sh    wait
 314                1        314      10786 3    0x80        ssh-agent  select
 220                1          1          0 3  0x4080            getty  ttyopn
 219                1        219          0 3  0x4082            getty   ttyin
 218                1        218          0 3  0x4082            getty   ttyin
 217                1        217      10786 3  0x4082             tcsh   ttyin
 216                1        216      10786 3  0x4082             tcsh   pause
 214                1        214          0 3    0x84             cron nanosle
 210                1        210          0 3    0x80            inetd  select
 185                1        185          0 3    0x84             apmd  select
 114                1        114          0 3    0x84          rpcbind  select
 110                1        110          0 3    0x84            named  select
 102                1        102          0 3    0x84          syslogd  select
 8                  0          0          0 3 0x20204         aiodoned aiodone
 7                  0          0          0 3 0x20204          ioflush  syncer
 6                  0          0          0 3 0x20204           reaper  reaper
 5                  0          0          0 3 0x20204       pagedaemon pgdaemo
 4                  0          0          0 3 0x20204             apm0   apmev
 3                  0          0          0 3 0x20204        cardslot0 cardslo
 2                  0          0          0 3 0x20204             usb0  usbevt
 1                  0          1          0 3  0x4080             init    wait
 0                 -1          0          0 3 0x20204          swapper schedul
db>  PID          COMMAND     EMUL  PRI UTIME STIME WAIT-MSG    WAIT-CHANNEL
 4893            find   netbsd   20   3.1  14.5 vnlock      0xc6d7c0bc
 4888        sendmail   netbsd   24   0.0   0.0 netio       0xc08d3250
 4887             tee   netbsd   24   0.0   0.0 netio       0xc08d40f8
 4886              sh   netbsd   32   0.0   0.0 wait        0xc6f17588
 4885              sh   netbsd   32   0.0   0.0 wait        0xc6f17ae0
 4884            cron   netbsd   24   0.0   0.0 netio       0xc08d4574
 4818            less   netbsd   50   0.0   0.0
 4802            less   netbsd   50   0.0   0.0
 4794            less   netbsd   50   0.0   0.0
 4792            less   netbsd   50   0.0   0.0
 4785            less   netbsd   50   0.0   0.0
 4780            less   netbsd   50   0.0   0.0
 4775            tcsh   netbsd   25   0.0   0.0 ttyin       0xc63f47cc
 4774           xterm   netbsd   24   0.4   0.1 select      selwait
 4769            less   netbsd   25   0.0   0.0 ttyin       0xc63f46b0
 4767            less   netbsd   50   0.1   0.0
 4766         objdump   netbsd   24   0.0   0.0 netio       0xc08d41c0
 4723            less   netbsd   50   0.0   0.0
 4659              nm   netbsd    4   0.0   0.0 uvn_fp2     0xc073eab0
 4656           tsort   netbsd   24   0.0   0.0 netio       0xc086b944
 4655              sh   netbsd   32   0.0   0.0 wait        0xc6eb13ac
 4654              sh   netbsd   32   0.0   0.0 wait        0xc6eb1acc
 4653              sh   netbsd   24   0.0   0.0 netio       0xc086bd1c
 4353            make   netbsd   32   0.0   0.0 wait        0xc6eb101c
 4352              sh   netbsd   32   0.0   0.0 wait        0xc6eb11e4
 4323            make   netbsd   32   0.0   0.0 wait        0xc6eb1c94
 4172            less   netbsd   50   0.0   0.0
 3943             ssh   netbsd   24   1.4   1.8 select      selwait
 3941        dhclient   netbsd   24   0.0   0.0 select      selwait
 3767             ssh   netbsd   24   0.1   0.0 netio       0xc08d43ac
 3766            less   netbsd   50   0.0   0.0
 3765             cvs   netbsd   24   0.0   0.0 netio       0xc08d4828
 3760             ssh   netbsd   24   0.0   0.0
 3759            less   netbsd   50   0.0   0.0
 3758             cvs   netbsd   24   0.0   0.0 netio       0xc086b77c
 3744            tcsh   netbsd   50   0.0   0.0
 3705              vi   netbsd   50   0.0   0.0
 2670        netscape    linux   24   0.0   0.0 select      selwait
 2669        netscape    linux   24 267.4  51.6 select      selwait
 1523           sshd1   netbsd   24   1.9   0.0 select      selwait
 398             tcsh   netbsd   40   0.2   0.1 pause       0xc6e75c84
 397            xterm   netbsd   24   5.6   2.5 select      selwait
 374              zhm   netbsd   24   0.0   0.2 select      selwait
 351             tcsh   netbsd   50   0.0   0.0
 334             tcsh   netbsd   40   0.0   0.0 pause       0xc6e75014
 333             tcsh   netbsd   40   0.0   0.0 pause       0xc6e5cc80
 332             tcsh   netbsd   25   0.0   0.2 ttyin       0xc63f4478
 331            xterm   netbsd   24   6.8   2.8 select      selwait
 330            xterm   netbsd   24   2.4   1.4 select      selwait
 329         xconsole   netbsd   24   0.0   0.0 select      selwait
 328           xclock   netbsd   24   0.2   0.2 select      selwait
 327              twm   netbsd   24   1.6   1.4 select      selwait
 321            xterm   netbsd   24   4.2   2.5 select      selwait
 318        XF86_SVGA   netbsd   24 219.2  37.0 select      selwait
 317            xinit   netbsd   32   0.0   0.0 wait        0xc6dfd008
 316               sh   netbsd   32   0.0   0.0 wait        0xc6c55c7c
 314        ssh-agent   netbsd   24   1.6   0.0 select      selwait
 220            getty   netbsd   25   0.0   0.0 ttyopn      0xc63f4008
 219            getty   netbsd   25   0.0   0.0 ttyin       0xc6d778f0
 218            getty   netbsd   25   0.0   0.0 ttyin       0xc6d777d4
 217             tcsh   netbsd   25   0.0   0.0 ttyin       0xc6d776b8
 216             tcsh   netbsd   40   0.0   0.0 pause       0xc6c3a31c
 214             cron   netbsd   32   0.0   0.4 nanosleep   nanowait.110
 210            inetd   netbsd   24   0.0   0.0 select      selwait
 185             apmd   netbsd   24   0.0   3.8 select      selwait
 114          rpcbind   netbsd   24   0.0   0.0 select      selwait
 110            named   netbsd   24   1.0   0.5 select      selwait
 102          syslogd   netbsd   24   0.0   0.4 select      selwait
 8           aiodoned   netbsd    4   0.0   0.2 aiodoned    uvm+0x54
 7            ioflush   netbsd   40   0.0  36.6 syncer      rushjob
 6             reaper   netbsd    4   0.0   0.1 reaper      deadproc
 5         pagedaemon   netbsd    4   0.0   0.5 pgdaemon    uvm+0x48
 4               apm0   netbsd   32   0.053305.7 apmev       0xc07c6400
 3          cardslot0   netbsd   32   0.0   3.1 cardslotev  0xc07b3344
 2               usb0   netbsd   32   0.0   0.0 usbevt      0xc07b38c0
 1               init   netbsd   32   0.0   0.0 wait        0xc6c36000
 0            swapper   netbsd    4   0.0   0.1 scheduler   proc0
db> 
Stopped at	cpu_Debugger+0x4:	leave	

Overnight, from 3am-9am, there were no exceptional logs. cron did the following:

Feb 11 03:00:00 zorkmid /USR/SBIN/CRON[4812]: (root) CMD (/usr/bin/newsyslog) 
Feb 11 03:00:00 zorkmid /USR/SBIN/CRON[4813]: (root) CMD (/usr/libexec/atrun) 
Feb 11 03:10:00 zorkmid /USR/SBIN/CRON[4829]: (root) CMD (/usr/libexec/atrun) 
Feb 11 03:20:00 zorkmid /USR/SBIN/CRON[4835]: (root) CMD (/usr/libexec/atrun) 
Feb 11 03:30:00 zorkmid /USR/SBIN/CRON[4838]: (root) CMD (/usr/libexec/atrun) 
Feb 11 03:36:00 zorkmid /USR/SBIN/CRON[4841]: (root) CMD (/usr/sbin/sendmail -q) 
Feb 11 03:40:00 zorkmid /USR/SBIN/CRON[4844]: (root) CMD (/usr/libexec/atrun) 
Feb 11 03:50:00 zorkmid /USR/SBIN/CRON[4847]: (root) CMD (/usr/libexec/atrun) 
Feb 11 04:00:00 zorkmid /USR/SBIN/CRON[4851]: (root) CMD (/usr/bin/newsyslog) 
Feb 11 04:00:00 zorkmid /USR/SBIN/CRON[4852]: (root) CMD (/usr/libexec/atrun) 
Feb 11 04:10:00 zorkmid /USR/SBIN/CRON[4856]: (root) CMD (/usr/libexec/atrun) 
Feb 11 04:20:00 zorkmid /USR/SBIN/CRON[4859]: (root) CMD (/usr/libexec/atrun) 
Feb 11 04:30:00 zorkmid /USR/SBIN/CRON[4862]: (root) CMD (/usr/libexec/atrun) 
Feb 11 04:36:00 zorkmid /USR/SBIN/CRON[4865]: (root) CMD (/usr/sbin/sendmail -q) 
Feb 11 04:40:00 zorkmid /USR/SBIN/CRON[4868]: (root) CMD (/usr/libexec/atrun) 
Feb 11 04:50:00 zorkmid /USR/SBIN/CRON[4873]: (root) CMD (/usr/libexec/atrun) 
Feb 11 05:00:00 zorkmid /USR/SBIN/CRON[4877]: (root) CMD (/usr/bin/newsyslog) 
Feb 11 05:00:00 zorkmid /USR/SBIN/CRON[4878]: (root) CMD (/usr/libexec/atrun) 
Feb 11 05:10:00 zorkmid /USR/SBIN/CRON[4882]: (root) CMD (/usr/libexec/atrun) 
Feb 11 05:15:00 zorkmid /USR/SBIN/CRON[4885]: (root) CMD (/bin/sh /etc/daily 2>&1 | tee /var/log/daily.out | sendmail -t) 
Feb 11 05:20:00 zorkmid /USR/SBIN/CRON[4895]: (root) CMD (/usr/libexec/atrun) 
Feb 11 05:30:00 zorkmid /USR/SBIN/CRON[4898]: (root) CMD (/usr/libexec/atrun) 
Feb 11 05:36:00 zorkmid /USR/SBIN/CRON[4901]: (root) CMD (/usr/sbin/sendmail -q) 
Feb 11 05:40:00 zorkmid /USR/SBIN/CRON[4904]: (root) CMD (/usr/libexec/atrun) 
Feb 11 05:50:00 zorkmid /USR/SBIN/CRON[4907]: (root) CMD (/usr/libexec/atrun) 
Feb 11 06:00:00 zorkmid /USR/SBIN/CRON[4911]: (root) CMD (/usr/bin/newsyslog) 
Feb 11 06:00:00 zorkmid /USR/SBIN/CRON[4912]: (root) CMD (/usr/libexec/atrun) 
Feb 11 06:10:00 zorkmid /USR/SBIN/CRON[4916]: (root) CMD (/usr/libexec/atrun) 
Feb 11 06:20:00 zorkmid /USR/SBIN/CRON[4919]: (root) CMD (/usr/libexec/atrun) 
Feb 11 06:30:00 zorkmid /USR/SBIN/CRON[4922]: (root) CMD (/usr/libexec/atrun) 
Feb 11 06:36:00 zorkmid /USR/SBIN/CRON[4925]: (root) CMD (/usr/sbin/sendmail -q) 
Feb 11 06:40:00 zorkmid /USR/SBIN/CRON[4928]: (root) CMD (/usr/libexec/atrun) 
Feb 11 06:50:00 zorkmid /USR/SBIN/CRON[4934]: (root) CMD (/usr/libexec/atrun) 
Feb 11 07:00:00 zorkmid /USR/SBIN/CRON[4938]: (root) CMD (/usr/bin/newsyslog) 
Feb 11 07:00:00 zorkmid /USR/SBIN/CRON[4939]: (root) CMD (/usr/libexec/atrun) 
Feb 11 07:10:00 zorkmid /USR/SBIN/CRON[4943]: (root) CMD (/usr/libexec/atrun) 
Feb 11 07:20:00 zorkmid /USR/SBIN/CRON[4946]: (root) CMD (/usr/libexec/atrun) 
Feb 11 07:30:00 zorkmid /USR/SBIN/CRON[4949]: (root) CMD (/usr/libexec/atrun) 
Feb 11 07:36:00 zorkmid /USR/SBIN/CRON[4952]: (root) CMD (/usr/sbin/sendmail -q) 
Feb 11 07:40:00 zorkmid /USR/SBIN/CRON[4955]: (root) CMD (/usr/libexec/atrun) 
Feb 11 07:50:00 zorkmid /USR/SBIN/CRON[4958]: (root) CMD (/usr/libexec/atrun) 
Feb 11 08:00:00 zorkmid /USR/SBIN/CRON[4962]: (root) CMD (/usr/bin/newsyslog) 
Feb 11 08:00:00 zorkmid /USR/SBIN/CRON[4963]: (root) CMD (/usr/libexec/atrun) 
Feb 11 08:10:00 zorkmid /USR/SBIN/CRON[4967]: (root) CMD (/usr/libexec/atrun) 
Feb 11 08:20:00 zorkmid /USR/SBIN/CRON[4972]: (root) CMD (/usr/libexec/atrun) 
Feb 11 08:30:00 zorkmid /USR/SBIN/CRON[4975]: (root) CMD (/usr/libexec/atrun) 
Feb 11 08:36:00 zorkmid /USR/SBIN/CRON[4978]: (root) CMD (/usr/sbin/sendmail -q) 
Feb 11 08:40:00 zorkmid /USR/SBIN/CRON[4981]: (root) CMD (/usr/libexec/atrun) 
Feb 11 08:50:00 zorkmid /USR/SBIN/CRON[4984]: (root) CMD (/usr/libexec/atrun) 
Feb 11 09:00:00 zorkmid /USR/SBIN/CRON[4988]: (root) CMD (/usr/bin/newsyslog) 
Feb 11 09:00:00 zorkmid /USR/SBIN/CRON[4989]: (root) CMD (/usr/libexec/atrun) 

Clearly /etc/daily didn't finish running:
zorkmid% ls -ld daily.out
-rw-r--r--  1 root  wheel  157 Feb 11 05:15 daily.out
zorkmid% cat daily.out
To: root
Subject: zorkmid.mit.edu daily output for Sun Feb 11 05:15:01 EST 2001


Uptime:  5:15AM up 2 days, 10:38, 7 users, load averages: 0.10, 0.09, 0.08
zorkmid% 


>Fix:
	None known at this time. PR is for tracking purposes.

>Release-Note:
>Audit-Trail:
>Unformatted: