Commit baf64b85 authored Jul 08, 2013 by Dave Hansen Committed by Ingo Molnar Jul 12, 2013

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>

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,

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