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Commit baf64b85 authored by Dave Hansen's avatar Dave Hansen Committed by Ingo Molnar
Browse files

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: default avatarDave 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: default avatarIngo Molnar <mingo@kernel.org>
parent 058ebd0e

arch/x86/kernel/nmi.c

+4 −3
Original line number Diff line number Diff line
@@ -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,