linux-kernel - [ 085/108] powerpc: Fix wrong divisor in usecs_to

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Message-Id: <20120723010704.366962842@decadent.org.uk>
Date:	Mon, 23 Jul 2012 02:08:16 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Andreas Schwab <schwab@...ux-m68k.org>,
	Anton Blanchard <anton@...ba.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Subject: [ 085/108] powerpc: Fix wrong divisor in usecs_to_cputime

3.2-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Andreas Schwab <schwab@...ux-m68k.org>

commit 9f5072d4f63f28d30d343573830ac6c85fc0deff upstream.

Commit d57af9b (taskstats: use real microsecond granularity for CPU times)
renamed msecs_to_cputime to usecs_to_cputime, but failed to update all
numbers on the way.  This causes nonsensical cpu idle/iowait values to be
displayed in /proc/stat (the only user of usecs_to_cputime so far).

This also renames __cputime_msec_factor to __cputime_usec_factor, adapting
its value and using it directly in cputime_to_usecs instead of doing two
multiplications.

Signed-off-by: Andreas Schwab <schwab@...ux-m68k.org>
Acked-by: Anton Blanchard <anton@...ba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@...nel.crashing.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/powerpc/include/asm/cputime.h |    6 +++---
 arch/powerpc/kernel/time.c         |   10 +++++-----
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/arch/powerpc/include/asm/cputime.h b/arch/powerpc/include/asm/cputime.h
index 1cf20bd..33a3580 100644
--- a/arch/powerpc/include/asm/cputime.h
+++ b/arch/powerpc/include/asm/cputime.h
@@ -126,11 +126,11 @@ static inline u64 cputime64_to_jiffies64(const cputime_t ct)
 /*
  * Convert cputime <-> microseconds
  */
-extern u64 __cputime_msec_factor;
+extern u64 __cputime_usec_factor;
 
 static inline unsigned long cputime_to_usecs(const cputime_t ct)
 {
-	return mulhdu(ct, __cputime_msec_factor) * USEC_PER_MSEC;
+	return mulhdu(ct, __cputime_usec_factor);
 }
 
 static inline cputime_t usecs_to_cputime(const unsigned long us)
@@ -143,7 +143,7 @@ static inline cputime_t usecs_to_cputime(const unsigned long us)
 	sec = us / 1000000;
 	if (ct) {
 		ct *= tb_ticks_per_sec;
-		do_div(ct, 1000);
+		do_div(ct, 1000000);
 	}
 	if (sec)
 		ct += (cputime_t) sec * tb_ticks_per_sec;
diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
index 9754743..567dd7c 100644
--- a/arch/powerpc/kernel/time.c
+++ b/arch/powerpc/kernel/time.c
@@ -158,13 +158,13 @@ EXPORT_SYMBOL_GPL(ppc_tb_freq);
 #ifdef CONFIG_VIRT_CPU_ACCOUNTING
 /*
  * Factors for converting from cputime_t (timebase ticks) to
- * jiffies, milliseconds, seconds, and clock_t (1/USER_HZ seconds).
+ * jiffies, microseconds, seconds, and clock_t (1/USER_HZ seconds).
  * These are all stored as 0.64 fixed-point binary fractions.
  */
 u64 __cputime_jiffies_factor;
 EXPORT_SYMBOL(__cputime_jiffies_factor);
-u64 __cputime_msec_factor;
-EXPORT_SYMBOL(__cputime_msec_factor);
+u64 __cputime_usec_factor;
+EXPORT_SYMBOL(__cputime_usec_factor);
 u64 __cputime_sec_factor;
 EXPORT_SYMBOL(__cputime_sec_factor);
 u64 __cputime_clockt_factor;
@@ -182,8 +182,8 @@ static void calc_cputime_factors(void)
 
 	div128_by_32(HZ, 0, tb_ticks_per_sec, &res);
 	__cputime_jiffies_factor = res.result_low;
-	div128_by_32(1000, 0, tb_ticks_per_sec, &res);
-	__cputime_msec_factor = res.result_low;
+	div128_by_32(1000000, 0, tb_ticks_per_sec, &res);
+	__cputime_usec_factor = res.result_low;
 	div128_by_32(1, 0, tb_ticks_per_sec, &res);
 	__cputime_sec_factor = res.result_low;
 	div128_by_32(USER_HZ, 0, tb_ticks_per_sec, &res);


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