Two processes are always created while running cygwin program(bash, ls, etc) under windows 2003 x64 R2

Two processes are always created while running cygwin program(bash, ls, etc) under windows 2003 x64 R2

[Oh, Choong-Hyun (HPSS-BSM)]

Dear all,

I found strange behavior of cywin application under windows 2003 x64 R2 version.
When I run bash, it creates parent bash process and also child bash process as like followings;


cmd.exe
  +- bash.exe
     +- bash.exe

services.exe
  +- cygrunsvr.exe
     +- cygrunsvr.exe


But on Windows 2008 x64 R2 system, it create only one process as like followings;
cmd.exe
  +- bash.exe

services.exe
  +- cygrunsvr.exe

So I am wondering whether it is normal behavior of cygwin on Windows 2003 x64 R2 system or not.
And also if so, what's a cause of this happening.

Thanks and regards,
ChoongHyun.

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Re: Two processes are always created while running cygwin program(bash, ls, etc) under windows 2003 x64 R2

[Corinna Vinschen]

On May  3 08:44, Oh, Choong-Hyun (HPSS-BSM) wrote:
> Dear all,
> 
> I found strange behavior of cywin application under windows 2003 x64 R2 version.
> When I run bash, it creates parent bash process and also child bash process as like followings;
> 
> 
> cmd.exe
>   +- bash.exe
>      +- bash.exe
> 
> services.exe
>   +- cygrunsvr.exe
>      +- cygrunsvr.exe
> 
> 
> But on Windows 2008 x64 R2 system, it create only one process as like followings;

I assume you mean non-64 bit here.

> cmd.exe
>   +- bash.exe
> 
> services.exe
>   +- cygrunsvr.exe
> 
> So I am wondering whether it is normal behavior of cygwin on Windows 2003 x64 R2 system or not.
> And also if so, what's a cause of this happening.

This happens if a Cygwin process (which is 32 bit and thus running in
the WOW64 environment) is called from a 64 bit Windows process.

On the older XP and 2003 64 bit systems, the first WOW64 processes
main thread started from a 64 bit process gets a stack address in the
range where usually the application itself resides.  This in turn
breaks Cygwin's fork.

Therefore a Cygwin process checks at process startup if it has been
started by a 64 bit parent process and if the stack address is in the
dangerous region.  If so, it re-spawns itself.  Since this second
process is started from another 32 bit process, its stack address is
useful again.  The intermediate process keeps in memory as long as the
re-spawned process runs.


Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Project Co-Leader          cygwin AT cygwin DOT com
Red Hat

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