On Wed, Oct 24, 2007 at 10:17:54PM +0400, Oleg Nesterov wrote: > On 10/24, Gautham R Shenoy wrote: > > > > On Wed, Oct 24, 2007 at 10:04:41AM -0700, Christoph Lameter wrote: > > > On Wed, 24 Oct 2007, Gautham R Shenoy wrote: > > > > > > > This is the version 2 of the refcount based cpu-hotplug "locking" > > > > implementation. > > > > > > Uggh. This introduces a global lock that has to be taken always when > > > scanning over cpus? > > > > Well, no! we take the global lock only while bumping up the refcount. > > We don't hold the lock while scanning over the cpus. And this is > > definitely an improvement over the lock_cpu_hotplug() global mutex > > we have now. > > Just to be sure I didn't miss something... preempt_disable() still works, > yes?
Yes it does. But it doesn't prevent onlining of new cpus. I am checking if __cpu_up() can also be called safely using stop_machine_run() so that we can use preempt_disable() for safe atomic access of the cpu_online_map. > > Oleg. > Thanks and Regards gautham. -- Gautham R Shenoy Linux Technology Center IBM India. "Freedom comes with a price tag of responsibility, which is still a bargain, because Freedom is priceless!" - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
