On 01/05/2013 04:06 PM, Russell King - ARM Linux wrote: > On Thu, Jan 03, 2013 at 06:58:38PM -0800, Srivatsa Vaddagiri wrote: >> I also think that the >> wait_for_completion() based wait in ARM's __cpu_die() can be replaced with a >> busy-loop based one, as the wait there in general should be terminated within >> few cycles. > > Why open-code this stuff when we have infrastructure already in the kernel > for waiting for stuff to happen? I chose to use the standard infrastructure > because its better tested, and avoids having to think about whether we need > CPU barriers and such like to ensure that updates are seen in a timely > manner. > > My stance on a lot of this idle/cpu dying code is that much of it can > probably be cleaned up and merged into a single common implementation - > in which case the use of standard infrastructure for things like waiting > for other CPUs do stuff is even more justified. On similar lines, Nikunj (in CC) and I had posted a patchset sometime ago to consolidate some of the CPU hotplug related code in the various architectures into a common standard implementation [1]. However, we ended up hitting a problem with Xen, because its existing code was unlike the other arch/ pieces [2]. At that time, we decided that we will first make the CPU online and offline paths symmetric in the generic code and then provide a common implementation of the duplicated bits in arch/, for the new CPU hotplug model [3]. I guess we should probably revisit it sometime, consolidating the code in incremental steps if not all at a time... -- [1]. http://lwn.net/Articles/500185/ [2]. http://thread.gmane.org/gmane.linux.kernel.cross-arch/14342/focus=14430 [3]. http://thread.gmane.org/gmane.linux.kernel.cross-arch/14342/focus=15567 Regards, Srivatsa S. Bhat
