On Dec 2 13:04, Eric Blake wrote: > On 12/02/2011 11:50 AM, Jon Clugston wrote: > > While this loop is running, the timestamp on "x.log" doesn't change > > (whereas on Linux it changes every 10 seconds). It sure looks to me > > that Windows just doesn't bother updating the file timestamp while it > > is open. I don't know if this update is required by POSIX - I would > > doubt that it is. > > POSIX requires that any write() to an open file mark it for update; the > update doesn't have to occur right away (so you can batch up several > writes, but only change the mtime metadata once at the end of the > batch), but it DOES require that stat() and several similar functions > flush all marked updates prior to exposing timestamps to the user. So > yes, Windows is violating POSIX, and I have no idea whether cygwin can > work around it.
You can change all file operations to use FILE_WRITE_THROUGH and FILE_NO_INTERMEDIATE_BUFFERING. Downside: No caching. All file operations must be sector aligned. Degraded system performance. Broken when a process has only write permissions. Alternatively, change write(2) so that every WriteFile call is accompanied by a FlushFileBuffers call. Downside: Extremly degraded write performance. Alternatively: Lie. That's how SUA does it. It has a background service running which (among other things) keeps track of write operations of SUA applications. If a SUA application calls write(2) the write timestamp is kept up to date internally, while the metadata on disk is still lagging in Windows style. A SUA application calling stat(2) gets a POSIX compatible timestamp. Non-SUA apps continue to show the "wrong" timestamp. If non-SUA apps write to a file, SUA apps also show the Windows timestamp. Cygwin could do the same. Downside: We don't have a mandatory background service running. Quite a hoop to jump through to implement a usually non-critical POSIX requirement. Corinna -- Corinna Vinschen Please, send mails regarding Cygwin to Cygwin Project Co-Leader cygwin AT cygwin DOT com Red Hat -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple
