[PATCH] x86-64: Use physflat on Intel for < 8 CPUs with CPU hotplug
This avoids races with the APIC broadcast/mask modes.
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/arch/x86_64/kernel/genapic.c b/arch/x86_64/kernel/genapic.c
index fe416fd..7a64ea1 100644
--- a/arch/x86_64/kernel/genapic.c
+++ b/arch/x86_64/kernel/genapic.c
@@ -104,9 +104,14 @@
* (We don't use lowest priority delivery + HW APIC IRQ steering, so
* can ignore the clustered logical case and go straight to physical.)
*/
- if (clusters <= 1 && max_cluster <= 8 && cluster_cnt[0] == max_cluster)
+ if (clusters <= 1 && max_cluster <= 8 && cluster_cnt[0] == max_cluster) {
+#ifdef CONFIG_HOTPLUG_CPU
+ /* Don't use APIC shortcuts in CPU hotplug to avoid races */
+ genapic = &apic_physflat;
+#else
genapic = &apic_flat;
- else
+#endif
+ } else
genapic = &apic_cluster;
print: