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Subject: Re: Race condition spawning childs/pipe stuff?
From: Max Kaehn <slothman AT electric-cloud DOT com>
To: cygwin AT cygwin DOT com
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Date: Fri, 10 Feb 2006 10:27:13 -0800
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In <http://www.cygwin.com/ml/cygwin/2005-10/msg00567.html>, Robert
Michelson wrote:
> I seem to encounter a race condition when running large recursive build
> processes (make).
> Occasionally, the build process hangs with a spawned child (sh.exe)
> eating with 100% user cpu.
> It seems the build command itself (spawned make) finished but
> child/parent? shell doesnt exit.
>
> When i kill sh.exe manually, the (recursive) build process continues and
> finishes.
> I suspect some kind of race condition somewhere in pipe stuff.

I've been getting the same thing with Cygwin 1.5.19-3, but it's
extremely hard to reproduce:  when doing endurance testing by repeatedly
building Mozilla, it only happened a single time on build #518 out of
570 (thus far).

Like Robert, I've found the problem to be in sync_proc_pipe(),
looping on low_priority_sleep().  This is the stack trace once
I munge $ebp and $eip to the highest-on-the-stack pair that
makes any sense:

#0  0x6106f0c7 in _pinfo::sync_proc_pipe () from /usr/bin/cygwin1.dll
#1  0x610972a9 in spawn_guts () from /usr/bin/cygwin1.dll
#2  0x61097655 in spawnve () from /usr/bin/cygwin1.dll
#3  0x61018c6b in execve () from /usr/bin/cygwin1.dll
#4  0x6108dd7f in _sigfe () from /usr/bin/cygwin1.dll
#5  0x004714c8 in ?? ()
#6  0x004715ec in ?? ()
#7  0xfffffffd in ?? ()
#8  0x00000002 in ?? ()
#9  0x0022eb98 in ?? ()
#10 0x004035c1 in fhandler_pipe::get_guard ()
#11 0x004715ec in ?? ()
#12 0x00470a24 in ?? ()
#13 0x004714c8 in ?? ()
#14 0x0041007c in fhandler_pipe::get_guard ()
#15 0x00000124 in ?? ()
#16 0x00000000 in ?? () from

Can anyone suggest other useful data to gather for the next time
this happens?

Thanks,
Max



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