On Mon, Oct 21, 2013 at 12:41 PM, Stefan Ruppert <sr@myarm.com> wrote:
Am 21.10.2013 16:22, schrieb Jeff Trawick:
On Mon, Oct 21, 2013 at 8:57 AM, <trawick@apache.org
<mailto:trawick@apache.org>> wrote:

    Author: trawick
    Date: Mon Oct 21 12:57:05 2013
    New Revision: 1534139

    URL: http://svn.apache.org/r1534139
    Log:
    Merge r960671 from trunk:

    Only deal with the mutex when XTHREAD is enabled. This increases the
    performance of buffered reads/writes tremendously.

    * file_io/win32/readwrite.c:
       (apr_file_read, apr_file_write): only manipulate mutex when XTHREAD

    Submitted by: Ivan Zhakov <ivan visualsvn.com <http://visualsvn.com>>


Trunk continues to allocate a mutex if buffered, even if the XTHREAD
flag is on (a minor detail I suppose).  That presumably is a simple fix
after double checking all the references to mutex or buffered in the
code used on Windows.  ISTR other concerns about the mutex or XTHREAD,
but I think this is an orthogonal issue.

Regarding exclusive access to a file under windows I filed a bug in 2010: https://issues.apache.org/bugzilla/show_bug.cgi?id=50058

Using the apr_file_lock()/apr_file_unlock() under Windows in append mode will deadlock the current thread! In the time of 2010 I just removed the apr_file_lock()/apr_file_unlock() code within the readwrite.c module. But a better solution is to support nesting within apr_file_lock()/apr_file_unlock() API calls!

Any comments?

Stefan


I thought it was this simple for append:

On Unix a lock isn't needed because the APR implementation there uses O_APPEND, which is atomic (subject to the size of the write I suppose)*; on Windows there's no such feature and APR has to use a lock to make it equivalent.  So the app shouldn't be getting a lock.

Is that consistent with what you see? 

*IIUC this isn't true for NFS

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