* Russell King - ARM Linux <linux@xxxxxxxxxxxxxxxx> [101006 15:25]: > On Wed, Oct 06, 2010 at 07:44:14AM -0700, Tony Lindgren wrote: > > * Russell King - ARM Linux <linux@xxxxxxxxxxxxxxxx> [101005 15:24]: > > > On Tue, Oct 05, 2010 at 03:19:52PM -0700, Tony Lindgren wrote: > > > > * Tony Lindgren <tony@xxxxxxxxxxx> [100907 20:04]: > > > > > This should not be needed when running on UP systems. > > > > > > > > > > Additionally we will also get an undefined instruction on ARM cores > > > > > without the extended CPUID registers with CONFIG_SMP_ON_UP. > > > > > > > > > > Also, we can now remove the is_smp() test from mmu.c. > > > > > > > > Just FYI, I've updated this one more time with to use cpus_empty > > > > instead of !smp_on_up() here as well. > > > > > > What's the rationale? > > > > With CPU hotplug if the other SMP cores are unplugged for PM or > > other reasons, no need to do the broadcast. > > Yes, but why this expensive test when the smp_on_up() is much cheaper? > > smp_call_function_many() already takes care of the "no other CPUs" > case, which is used by on_each_cpu_mask() and on_each_cpu(), which > means these functions won't broadcast the operations to other CPUs > when they're offline. > > In any case, if you think that we broadcast every operation to all > CPUs, you're mistaken - TLB and cache ops are broadcast to only > those CPUs which the thread is running on, or in the case of non-MM > specific, to all online CPUs. OK thanks, that's what I was missing. > So the only thing we have to worry about is "is there an ID register > available" which is covered by the is_smp() test. Checking the CPU > mask is far more expensive and imho ends up needlessly adding to the > complexity. OK. In that case, the patch to use is the previous one: http://www.arm.linux.org.uk/developer/patches/viewpatch.php?id=6429/1 Regards, Tony -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
