perf/x86: Fix incorrect use of do_div() in NMI warning

I completely botched understanding the calling conventions of
do_div().  I assumed that do_div() returned the result instead
of realizing that it modifies its argument and returns a
remainder.  The side-effect from this would be bogus numbers
for the "msecs" value in the warning messages:

	INFO: NMI handler (perf_event_nmi_handler) took too long to run: 0.114 msecs

Note, there was a second fix posted by Stephane Eranian for
a separate patch which I also botched:

	http://lkml.kernel.org/r/20130704223010.GA30625@quad

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Dave Hansen <dave@sr71.net>
Link: http://lkml.kernel.org/r/20130708214404.B0B6EA66@viggo.jf.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/kernel/nmi.c b/arch/x86/kernel/nmi.c
index 0920212..ba77ebc 100644 (file)
--- a/arch/x86/kernel/nmi.c
+++ b/arch/x86/kernel/nmi.c
@@ -111,7 +111,7 @@ static int __kprobes nmi_handle(unsigned int type, struct pt_regs *regs, bool b2
         */
        list_for_each_entry_rcu(a, &desc->head, list) {
                u64 before, delta, whole_msecs;
-               int decimal_msecs, thishandled;
+               int remainder_ns, decimal_msecs, thishandled;
 
                before = local_clock();
                thishandled = a->handler(type, regs);
@@ -123,8 +123,9 @@ static int __kprobes nmi_handle(unsigned int type, struct pt_regs *regs, bool b2
                        continue;
 
                nmi_longest_ns = delta;
-               whole_msecs = do_div(delta, (1000 * 1000));
-               decimal_msecs = do_div(delta, 1000) % 1000;
+               whole_msecs = delta;
+               remainder_ns = do_div(whole_msecs, (1000 * 1000));
+               decimal_msecs = remainder_ns / 1000;
                printk_ratelimited(KERN_INFO
                        "INFO: NMI handler (%ps) took too long to run: "
                        "%lld.%03d msecs\n", a->handler, whole_msecs,