[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>

1 files changed, 20 insertions, 0 deletions

diff --git a/kernel/softirq.c b/kernel/softirq.c
index ad3295cdded5..ec8fed42a86f 100644
--- a/kernel/softirq.c
+++ b/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