On Wed, 13 Apr 2005, Pete Zaitcev wrote: > On Tue, 12 Apr 2005 09:50:15 -0400 (EDT) Alan Stern <[EMAIL PROTECTED]> wrote: > > > What about the question of making sure that I/O operations complete before > > starting a delay loop, like this: > > > > outw(..., ...); > > mb(); > > udelay(10); > > > > Is the mb() sufficient to insure that the data will be written to the > > device before the udelay() call begins? > > The mb() has nothing to do with outw() in theory, although implementations > may accomplish it as a side effect. Just drop the mb().
Is it true then, on all architectures, that the hardware will complete the outw() _before_ the CPU executes the udelay() routine, even without the mb()? Or does it not really matter, because the outw() will complete within a handful of CPU cycles anyway, long before the 10 us delay is over? I want to avoid pathological situations where the hardware reorders the I/O write to occur _after_ the delay loop. Apparently some architectures have very loose ordering guarantees for I/O operations with respect to memory operations. Alan Stern ------------------------------------------------------- SF email is sponsored by - The IT Product Guide Read honest & candid reviews on hundreds of IT Products from real users. Discover which products truly live up to the hype. Start reading now. http://ads.osdn.com/?ad_id=6595&alloc_id=14396&op=click _______________________________________________ linux-usb-devel@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
