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Date: Wed, 01 Mar 2006 10:47:59 -0500
From: Paul Clements <paul DOT clements AT steeleye DOT com>
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Subject: Re: Shells hang during script execution
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Christopher Faylor wrote:

> It's also in the latest snapshot:  http://cygwin.com/snapshots/

I got the latest cygwin dll snapshot (20060227) a few days ago and I've 
been stress testing ksh with this new dll since.

The good news is that the hang issues (signal related) that I was seeing 
appear to be fixed by your patches. I've not seen the either of the two 
hangs with this snapshot. Thanks Christopher.

The bad news is that I'm now seeing a segmentation violation (4 or 5 
times so far) that I was not seeing before. I don't know if fixing the 
hangs has allowed me to get to this point, or if the crashes are due to 
the patches (hard to see how that could be the case). I'm having trouble 
figuring out how the crash occurred, because the last address in the 
stackdump looks bogus. I'm not sure if there's any significance to that 
(could it be a signal handler that was injected into the stack, or could 
this be due to stack corruption, or does this look normal?). Anyway, 
below is the stack trace and (very simple) test script I'm running. Any 
ideas or suggestions on things to try?

--
Paul


$ cat ksh.exe.stackdump
Exception: STATUS_ACCESS_VIOLATION at eip=0022FBFC
eax=00000000 ebx=FFFFFFFF ecx=610FE084 edx=0022F064 esi=00484283 
edi=00486C1D
ebp=0022E848 esp=0022E830 program=c:\lk\bin\ksh.exe, pid 1816, thread main
cs=001B ds=0023 es=0023 fs=003B gs=0000 ss=0023
Stack trace:
Frame     Function  Args
0022E848  0022FBFC  (00484660, 00000000, 0009C05C, 0041E1F2)
0022E938  0040AB39  (00486C18, 0022E950, 00000020, 004896C8)
0022E968  0040A0FA  (00486C18, 00000020, 004895F0, 00000000)
0022E9B8  0040CFA8  (00486C50, 00000000, 00486B38, 00000000)
0022EA38  0040C4C1  (00486C50, 00000000, 004895F4, 00000100)
0022EAB8  0040C665  (00486C80, 00000000, 00486888, 00000000)
0022EB38  0040CAFD  (004867B8, 00000000, 0022EB88, 00000003)
0022EBB8  0040C68E  (004867B8, 00000000, 0022EBE8, 0041A317)
0022EC38  0040C68E  (00487350, 00000000, 0022EC68, 00416A9A)
0022EC68  004166FB  (004850E8, 00000001, 00000000, 00000030)
0022EEC8  004162B2  (00000002, 6115E7B4, 00480090, 77DBD397)
0022EF78  61005BC8  (0022EFD0, 0022EFFC, C0150008, 00000000)
0022FF88  61005EB3  (00000000, 00000000, 00000000, 00000000)
End of stack trace


Corresponding symbols:

22fbfc ??     (this address looks bogus)
40ab39 expand (40ab39 is after the call to waitlast)
40a0fa evalstr
40cfa8 comexec


The test case is very simple. I just run three copies of ksh like this:

ksh ./test.sh

--- test.sh ---

n=${1:-10000000}
i=0
while [ $i -lt $n ]
do
         x=`echo a:$i | cut -d: -f1`
         i=$(( $i + 1 ))
         m=$(( $i % 1000 ))
         if [ $m -eq 0 ]; then echo -n $i: $$:; date; fi
done


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