sched/x86: Calculate booted cores after construction of sibling_mask

Commit 316ad248307fb ("sched/x86: Rewrite set_cpu_sibling_map()")
broke the booted_cores accounting.

The problem is that the booted_cores accounting needs all the
sibling links set up. So restore the second loop and add a comment as
to why its needed.

On qemu booted with -smp sockets=1,cores=2,threads=2;
Before:
 $ grep cores /proc/cpuinfo
 cpu cores       : 2
 cpu cores       : 1
 cpu cores       : 4
 cpu cores       : 3

With the patch:
 $ grep cores /proc/cpuinfo
 cpu cores       : 2
 cpu cores       : 2
 cpu cores       : 2
 cpu cores       : 2

Reported-by: Prarit Bhargava <prarit@redhat.com>
Reported-by: Borislav Petkov <bp@amd64.org>
Signed-off-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20120531073738.GH7511@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 9 insertions, 0 deletions

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index fd019d78b1f4..3fab55bea29b 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -382,6 +382,15 @@ void __cpuinit set_cpu_sibling_map(int cpu)
                 if ((i == cpu) || (has_mc && match_llc(c, o)))
                         link_mask(llc_shared, cpu, i);
 
+        }
+
+        /*
+         * This needs a separate iteration over the cpus because we rely on all
+         * cpu_sibling_mask links to be set-up.
+         */
+        for_each_cpu(i, cpu_sibling_setup_mask) {
+                o = &cpu_data(i);
+
                 if ((i == cpu) || (has_mc && match_mc(c, o))) {
                         link_mask(core, cpu, i);