On Fri, 2015-02-13 at 13:56 -0800, Davidlohr Bueso wrote: > On Thu, 2015-02-12 at 20:59 +0100, Oleg Nesterov wrote: > > Commit de30ec47302c "Remove unnecessary ->wait.lock serialization when > > reading completion state" was not correct, without lock/unlock the code > > like stop_machine_from_inactive_cpu() > > > > while (!completion_done()) > > cpu_relax(); > > > > can return before complete() finishes its spin_unlock() which writes to > > this memory. And spin_unlock_wait(). > > How about reverting the patch altogether? > > This was never a problem nor have I ever seen a performance issues in > completions that would merit these lockless checks. The commit changelog > has *zero* information, so I don't know if this was ever a real issue. >
hmm I guess you're patch is more optimal tho, because we don't update the lock, less cacheline bouncing issues etc. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
