> -----Original Message-----
> From: Stefan Ruppert [mailto:[email protected]]
> Sent: vrijdag 8 oktober 2010 17:55
> To: [email protected]
> Subject: Re: apr_file_*() threading issues under Windows!
>
> I do not use a file handle from different threads. But if this is not a
> valid usage scenario why protected some piece of code with a mutex??
>
> Also a couple of weeks ago there was a discussion about performance
> where these mutex operation are involved. Thus if the apr_file_*()
> functions are designed to be not thread-safe, why use mutexes at all??
>
> I personally prefer that the application has to decide if it uses a
> file
> from different threads and therefore has to protect the operations by
> itselt.
In the early days of APR, httpd used threads on Windows and workers on other
systems. And most likely to keep things easy mutexes were used to protect the
file handles in some Windows scenarios. (If you look at the history you will
find that some other OSs had mutexes too, but those were removed over the years)
The only documented safe way to use a file in multiple threads at once (that
should work on multiple Oss) is with APR_FOPEN_XTHREAD.
The mutexes are currently slowing down IO on Windows; especially on multi
CPU-systems, because they were simply never removed for Windows. And I would
really like to see them removed where possible. (Ivan Zhakov already started
working on this for some Subversion performance critical code paths)
Bert
