[PATCH] on_each_cpu(): disable local interrupts

When on_each_cpu() runs the callback on other CPUs, it runs with local
interrupts disabled.  So we should run the function with local interrupts
disabled on this CPU, too.

And do the same for UP, so the callback is run in the same environment on both
UP and SMP.  (strictly it should do preempt_disable() too, but I think
local_irq_disable is sufficiently equivalent).

Also uninlines on_each_cpu().  softirq.c was the most appropriate file I could
find, but it doesn't seem to justify creating a new file.

Oh, and fix up that comment over (under?) x86's smp_call_function().  It
drives me nuts.

Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/i386/kernel/smp.c

@@ -506,25 +506,21 @@ void unlock_ipi_call_lock(void)
 
 static struct call_data_struct *call_data;
 
-/*
- * this function sends a 'generic call function' IPI to all other CPUs
- * in the system.
- */
-
-int smp_call_function (void (*func) (void *info), void *info, int nonatomic,
-			int wait)
-/*
- * [SUMMARY] Run a function on all other CPUs.
- * <func> The function to run. This must be fast and non-blocking.
- * <info> An arbitrary pointer to pass to the function.
- * <nonatomic> currently unused.
- * <wait> If true, wait (atomically) until function has completed on other CPUs.
- * [RETURNS] 0 on success, else a negative status code. Does not return until
+/**
+ * smp_call_function(): Run a function on all other CPUs.
+ * @func: The function to run. This must be fast and non-blocking.
+ * @info: An arbitrary pointer to pass to the function.
+ * @nonatomic: currently unused.
+ * @wait: If true, wait (atomically) until function has completed on other CPUs.
+ *
+ * Returns 0 on success, else a negative status code. Does not return until
  * remote CPUs are nearly ready to execute <<func>> or are or have executed.
  *
  * You must not call this function with disabled interrupts or from a
  * hardware interrupt handler or from a bottom half handler.
  */
+int smp_call_function (void (*func) (void *info), void *info, int nonatomic,
+			int wait)
 {
 	struct call_data_struct data;
 	int cpus;

include/linux/smp.h

@@ -52,23 +52,12 @@ extern void smp_cpus_done(unsigned int max_cpus);
 /*
  * Call a function on all other processors
  */
-extern int smp_call_function (void (*func) (void *info), void *info,
-			      int retry, int wait);
+int smp_call_function(void(*func)(void *info), void *info, int retry, int wait);
 
 /*
  * Call a function on all processors
  */
-static inline int on_each_cpu(void (*func) (void *info), void *info,
-			      int retry, int wait)
-{
-	int ret = 0;
-
-	preempt_disable();
-	ret = smp_call_function(func, info, retry, wait);
-	func(info);
-	preempt_enable();
-	return ret;
-}
+int on_each_cpu(void (*func) (void *info), void *info, int retry, int wait);
 
 #define MSG_ALL_BUT_SELF	0x8000	/* Assume <32768 CPU's */
 #define MSG_ALL			0x8001
@@ -94,7 +83,13 @@ void smp_prepare_boot_cpu(void);
 #define raw_smp_processor_id()			0
 #define hard_smp_processor_id()			0
 #define smp_call_function(func,info,retry,wait)	({ 0; })
-#define on_each_cpu(func,info,retry,wait)	({ func(info); 0; })
+#define on_each_cpu(func,info,retry,wait)	\
+	({					\
+		local_irq_disable();		\
+		func(info);			\
+		local_irq_enable();		\
+		0;				\
+	})
 static inline void smp_send_reschedule(int cpu) { }
 #define num_booting_cpus()			1
 #define smp_prepare_boot_cpu()			do {} while (0)

kernel/softirq.c

@@ -16,6 +16,7 @@
 #include <linux/cpu.h>
 #include <linux/kthread.h>
 #include <linux/rcupdate.h>
+#include <linux/smp.h>
 
 #include <asm/irq.h>
 /*
@@ -495,3 +496,22 @@ __init int spawn_ksoftirqd(void)
 	register_cpu_notifier(&cpu_nfb);
 	return 0;
 }
+
+#ifdef CONFIG_SMP
+/*
+ * Call a function on all processors
+ */
+int on_each_cpu(void (*func) (void *info), void *info, int retry, int wait)
+{
+	int ret = 0;
+
+	preempt_disable();
+	ret = smp_call_function(func, info, retry, wait);
+	local_irq_disable();
+	func(info);
+	local_irq_enable();
+	preempt_enable();
+	return ret;
+}
+EXPORT_SYMBOL(on_each_cpu);
+#endif