On Thu, Jan 16, 2014 at 04:08:20PM -0800, Tim Chen wrote: > Remove unnecessary operation and make the cmpxchg(lock, node, NULL) == node > check in mcs_spin_unlock() likely() as it is likely that a race did not occur > most of the time. It might be good to describe why the node->locked=1 is thought unnecessary. I concur it is, but upon reading this changelog I was left wondering and had to go read the code and run through the logic to convince myself. Having done so, I'm now wondering if we think so for the same reason -- although I'm fairly sure we are. The argument goes like: everybody only looks at his own ->locked value, therefore the only one possibly interested in node->locked is the lock owner. However the lock owner doesn't care what's in it, it simply assumes its 1 but really doesn't care one way or another. That said, a possible DEBUG mode might want to actually set it, validate that all other linked nodes are 0 and upon unlock verify the same before flipping next->locked to 1. -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
