Commit-ID: baf64b85445546a38b44052d71782dfe7531e350
Gitweb: http://git.kernel.org/tip/baf64b85445546a38b44052d71782dfe7531e350
Author: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
AuthorDate: Mon, 8 Jul 2013 14:44:04 -0700
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Fri, 12 Jul 2013 14:13:04 +0200
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@xxxxxxxxxxxxxxx>
Cc: Dave Hansen <dave@xxxxxxxx>
Link: http://lkml.kernel.org/r/20130708214404.B0B6EA66@xxxxxxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
arch/x86/kernel/nmi.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kernel/nmi.c b/arch/x86/kernel/nmi.c
index 0920212..ba77ebc 100644
--- 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,
--
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