On Sat, Mar 26, 2011 at 12:19 AM, Greg KH <greg@xxxxxxxxx> wrote: > On Sat, Mar 26, 2011 at 01:19:31AM +0300, Dan Carpenter wrote: >> On Fri, Mar 25, 2011 at 01:52:57PM +0100, Roland Vossen wrote: >> > >> >> > >>>+ if (likely(hw != NULL)) >> > >>>+ wl = hw->priv; >> > >> >> > >>This isn't a fast path. The likely() here is not needed. It makes the >> > >>code less readable for no reason. >> > > >> > >Good suggestion. Agree. >> > >> > Come to think about it a bit better: I would say that the 'likely' >> > makes the code more readable since it indicates to the reader what >> > the 'sunny flow' is. Is there a common consensus on the usage of >> > likely/unlikely ? > > The consensus is that is should NEVER show up in a driver. > > Really, don't use it, 90% of the time it is used wrong. That other 10% > is just lucky. The compiler knows this stuff better than we do, so let > it handle it properly. > > Again, never use it in a driver. If you really want to, you had better > have hard numbers as to why it matters showing a noticable improvement. > > thanks, > > greg k-h Plus, IIRC the WARN_ON() macro already wraps its condition into unlikely(), so unlikely(WARN_ON()) will expand into something like if(unlikely(unlikely(...))... -- Vista: [V]iruses, [I]ntruders, [S]pyware, [T]rojans and [A]dware. :-) _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/devel
