[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 (file)
--- a/arch/x86_64/kernel/genapic.c
+++ b/arch/x86_64/kernel/genapic.c
@@ -104,9 +104,14 @@ void __init clustered_apic_check(void)
         * (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: