RE: [ros-dev] Re: [ros-diffs] [gedmurphy] 19312: Improve stopping control of the service

[Murphy, Ged (Bolton)]

>   -----Original Message-----
>  From: Thomas Weidenmueller [mailto:[e-mail]] 
>  Sent: 18 November 2005 12:03
>  To: ReactOS Development List
>  Subject: Re: [ros-dev] Re: [ros-diffs] [gedmurphy] 19312: 
>  Improve stopping control of the service
>  
>  
>  Murphy, Ged (Bolton) wrote:
> >   This function is new to me.  
>  Now that
> you're writing multithreaded code it's about time to learn
>  about these functions ;)
>  
> >   I'm just doing a bit of research on it now to
> > better  
>  understand it, but
> >   could you just give me a bit of background of the
> >  
>  difference between this,
> >   and using something like a mutex or CS, and why
> > it's better in this
> >  scenario? 
>  Of course you can use mutexes or critical sections, but for 
>  this purpose
>  interlocked operations are much more lightweight because with 
>  mutexes or
>  critical sections you'd have to protect the read operation as 
>  well. The
>  Interlocked* functions basically guarantee that a certain 
>  operation on a
>  variable shared by multiple threads is performed in an atomic 
>  matter. I
>  probably should mention that reads are always atomic, so reading a
>  variable with the size smaller or equal as the size of a 
>  general purpose
>  register does not need to be protected, writes however have 
>  to be protected.
>  
>  You should read the following articles:
>  http://msdn.microsoft.com/library/default.asp?url=/library/en-
>  us/dllproc/base/interlocked_variable_access.asp
>  http://blogs.msdn.com/oldnewthing/archive/2004/09/15/229915.aspx 

Thanks for the info, much appreciated.
I've been reading up on Interlocked Variable Access this morning and have
now implemented it into the code.

Ged.



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