> > Ooooh. And I just noticed include/linux/percpu-rwsem.h which does > > something similar. Certainly it was not in my tree when I started > > this patch... percpu_down_write() doesn't allow multiple writers, > > but the main problem it uses msleep(1). It should not, I think. > > > > But. It seems that percpu_up_write() is equally wrong? Doesn't > > it need synchronize_rcu() before "p->locked = false" ? > > > > (add Mikulas) > > Mikulas said something about doing an updated patch, so I figured I > would look at his next version. > > Thanx, Paul
The best ideas proposed in this thread are: Using heavy/light barries by Lai Jiangshan. This fixes the missing barrier bug, removes the ugly test "#if defined(X86) ..." and makes the read path use no barrier instruction on all architectures. Instead of rcu_read_lock, we can use rcu_read_lock_sched (or preempt_disable) - the resulting code is smaller. The critical section is so small that there is no problem disabling preemption. I am sending these two patches. Linus, please apply them if there are no objections. Mikulas -- 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/
