[tip:sched/urgent] sched/x86: Calculate booted cores after construction of sibling_mask

[tip-bot for Kamalesh Babulal]

Commit-ID:  ceb1cbac8eda66cf0f889def226b4e82f8ff857b
Gitweb:     http://git.kernel.org/tip/ceb1cbac8eda66cf0f889def226b4e82f8ff857b
Author:     Kamalesh Babulal <kamalesh@xxxxxxxxxxxxxxxxxx>
AuthorDate: Thu, 31 May 2012 13:07:38 +0530
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Wed, 6 Jun 2012 16:37:59 +0200

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@xxxxxxxxxx>
Reported-by: Borislav Petkov <bp@xxxxxxxxx>
Signed-off-by: Kamalesh Babulal <kamalesh@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Link: http://lkml.kernel.org/r/20120531073738.GH7511@xxxxxxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 arch/x86/kernel/smpboot.c |    9 +++++++++
 1 files changed, 9 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index fd019d7..3fab55b 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);
 
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