On Tue, 6 Jan 2009, Matthew Wilcox wrote: > > > > This looks ugly. Why doesn't __mutex_lock_common() just set the lock > > owner? Hate seeing it done in the caller that has to re-compute common > > (yeah, yeah, it's cheap) and just looks ugly. > > Because __mutex_lock_common() is the slow path. The fast path is a > couple of assembly instructions in asm/mutex.h. If the lock isn't > contended, it will never call __mutex_lock_common(). No, that's not it. Look at the callers. They are _all_ the slow path. They looked like this: might_sleep(); return __mutex_lock_common(lock, TASK_KILLABLE, subclass, _RET_IP_); Yes, you _also_ need to set the owner in the fast-path, but that's all entirely different. This is the debug case, which _always_ calls the slow-path. So what I'm saying is that the slow-path should just set it. And then yes, we _also_ need to set it in the fast-path, but at least we don't need to set it in all the debug versions that just call the slow path! Linus -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
