smp, generic: introduce arch_disable_smp_support() instead of disable_ioapic_setup()

Impact: cleanup

disable_ioapic_setup() in init/main.c is ugly as the function is
x86-specific. The #ifdef inline prototype there is ugly too.

Replace it with a generic arch_disable_smp_support() function - which
has a weak alias for non-x86 architectures and for non-ioapic x86 builds.

Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/include/asm/io_apic.h

diff --git a/arch/x86/include/asm/io_apic.h b/arch/x86/include/asm/io_apic.h
index 08ec793..309d0e2 100644
--- a/arch/x86/include/asm/io_apic.h
+++ b/arch/x86/include/asm/io_apic.h
@@ -143,15 +143,6 @@
 /* 1 if the timer IRQ uses the '8259A Virtual Wire' mode */
 extern int timer_through_8259;
 
-static inline void disable_ioapic_setup(void)
-{
-#ifdef CONFIG_PCI
-	noioapicquirk = 1;
-	noioapicreroute = -1;
-#endif
-	skip_ioapic_setup = 1;
-}
-
 /*
  * If we use the IO-APIC for IRQ routing, disable automatic
  * assignment of PCI IRQ's.

arch/x86/kernel/apic.c

diff --git a/arch/x86/kernel/apic.c b/arch/x86/kernel/apic.c
index 85d8b50..a04a73a 100644
--- a/arch/x86/kernel/apic.c
+++ b/arch/x86/kernel/apic.c
@@ -1138,9 +1138,7 @@
 	int i, j;
 
 	if (disable_apic) {
-#ifdef CONFIG_X86_IO_APIC
-		disable_ioapic_setup();
-#endif
+		arch_disable_smp_support();
 		return;
 	}
 

arch/x86/kernel/io_apic.c

diff --git a/arch/x86/kernel/io_apic.c b/arch/x86/kernel/io_apic.c
index 57d60c7..84bccac 100644
--- a/arch/x86/kernel/io_apic.c
+++ b/arch/x86/kernel/io_apic.c
@@ -98,10 +98,19 @@
 
 int skip_ioapic_setup;
 
+void arch_disable_smp_support(void)
+{
+#ifdef CONFIG_PCI
+	noioapicquirk = 1;
+	noioapicreroute = -1;
+#endif
+	skip_ioapic_setup = 1;
+}
+
 static int __init parse_noapic(char *str)
 {
 	/* disable IO-APIC */
-	disable_ioapic_setup();
+	arch_disable_smp_support();
 	return 0;
 }
 early_param("noapic", parse_noapic);

arch/x86/kernel/smpboot.c

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index f40f86f..96f7d30 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -1071,7 +1071,7 @@
 		printk(KERN_ERR "... forcing use of dummy APIC emulation."
 				"(tell your hw vendor)\n");
 		smpboot_clear_io_apic();
-		disable_ioapic_setup();
+		arch_disable_smp_support();
 		return -1;
 	}
 

include/linux/smp.h

diff --git a/include/linux/smp.h b/include/linux/smp.h
index 715196b..d41a3a8 100644
--- a/include/linux/smp.h
+++ b/include/linux/smp.h
@@ -67,6 +67,12 @@
 extern void smp_cpus_done(unsigned int max_cpus);
 
 /*
+ * Callback to arch code if there's nosmp or maxcpus=0 on the
+ * boot command line:
+ */
+extern void arch_disable_smp_support(void);
+
+/*
  * Call a function on all other processors
  */
 int smp_call_function(void(*func)(void *info), void *info, int wait);

init/main.c

diff --git a/init/main.c b/init/main.c
index bfe4fb0..6441083 100644
--- a/init/main.c
+++ b/init/main.c
@@ -136,14 +136,14 @@
  * greater than 0, limits the maximum number of CPUs activated in
  * SMP mode to <NUM>.
  */
-#ifndef CONFIG_X86_IO_APIC
-static inline void disable_ioapic_setup(void) {};
-#endif
+
+void __weak arch_disable_smp_support(void) { }
 
 static int __init nosmp(char *str)
 {
 	setup_max_cpus = 0;
-	disable_ioapic_setup();
+	arch_disable_smp_support();
+
 	return 0;
 }
 
@@ -153,14 +153,14 @@
 {
 	get_option(&str, &setup_max_cpus);
 	if (setup_max_cpus == 0)
-		disable_ioapic_setup();
+		arch_disable_smp_support();
 
 	return 0;
 }
 
 early_param("maxcpus", maxcpus);
 #else
-#define setup_max_cpus NR_CPUS
+const unsigned int setup_max_cpus = NR_CPUS;
 #endif
 
 /*