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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>
This commit is contained in:
Dave Hansen 2013-07-08 14:44:04 -07:00 committed by Ingo Molnar
parent 058ebd0eba
commit baf64b8544
1 changed files with 4 additions and 3 deletions
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7
arch/x86/kernel/nmi.c
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@ -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,