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| author | Dave Hansen <dave.hansen@linux.intel.com> | 2013-07-08 23:44:04 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2013-07-12 14:13:04 +0200 |
| commit | baf64b85445546a38b44052d71782dfe7531e350 (patch) | |
| tree | 123db75d91d993ec405500d609c67844488db216 | |
| parent | perf: Fix perf_lock_task_context() vs RCU (diff) | |
| download | linux-baf64b85445546a38b44052d71782dfe7531e350.tar.xz linux-baf64b85445546a38b44052d71782dfe7531e350.zip | |
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>
| -rw-r--r-- | arch/x86/kernel/nmi.c | 7 |
1 files changed, 4 insertions, 3 deletions
diff --git a/arch/x86/kernel/nmi.c b/arch/x86/kernel/nmi.c index 0920212e6159..ba77ebc2c353 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, |