[PATCH] lockstat - fix numerical output rounding error

From: Joe Korty
Date: Mon Aug 25 2008 - 17:49:47 EST


Fix rounding error in /proc/lock_stat numerical output.

On occasion the two digit fractional part contains the three
digit value '100'. This is due to a bug in the rounding algorithm
which pushes values in the range '95..99' to '100' rather than
to '00' + an increment to the integer part. For example,

- 123456.100 old display
+ 123457.00 new display

Index: 2.6.26/kernel/lockdep_proc.c
===================================================================
--- 2.6.26.orig/kernel/lockdep_proc.c 2008-07-13 17:51:29.000000000 -0400
+++ 2.6.26/kernel/lockdep_proc.c 2008-08-25 16:58:04.000000000 -0400
@@ -406,8 +406,9 @@
{
unsigned long rem;

+ nr += 5; /* for display rounding */
rem = do_div(nr, 1000); /* XXX: do_div_signed */
- snprintf(buf, bufsiz, "%lld.%02d", (long long)nr, ((int)rem+5)/10);
+ snprintf(buf, bufsiz, "%lld.%02d", (long long)nr, (int)rem/10);
}

static void seq_time(struct seq_file *m, s64 time)
--
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