On 03/05, Lai Jiangshan wrote: > > On 03/03/13 01:06, Oleg Nesterov wrote: > > On 03/02, Michel Lespinasse wrote: > >> > >> My version would be slower if it needs to take the > >> slow path in a reentrant way, but I'm not sure it matters either :) > > > > I'd say, this doesn't matter at all, simply because this can only happen > > if we race with the active writer. > > It can also happen when interrupted. (still very rarely) > > arch_spin_trylock() > ------->interrupted, > __this_cpu_read() returns 0. > arch_spin_trylock() fails > slowpath, any nested will be slowpath too. > ... > ..._read_unlock() > <-------interrupt > __this_cpu_inc() > .... Yes sure. Or it can take the local lock after we already take the global fallback_lock. But the same can happen with FALLBACK_BASE, just because we need to take a lock (local or global) first, then increment the counter. > (I worries to much. I tend to remove FALLBACK_BASE now, we should > add it only after we proved we needed it, this part is not proved) Agreed, great ;) Oleg. -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
