This is a note to let you know that I've just added the patch titled
time: Fix overflow when HZ is smaller than 60
to the 3.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
time-fix-overflow-when-hz-is-smaller-than-60.patch
and it can be found in the queue-3.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 80d767d770fd9c697e434fd080c2db7b5c60c6dd Mon Sep 17 00:00:00 2001
From: Mikulas Patocka <mpatocka@xxxxxxxxxx>
Date: Fri, 24 Jan 2014 16:41:36 -0500
Subject: time: Fix overflow when HZ is smaller than 60
From: Mikulas Patocka <mpatocka@xxxxxxxxxx>
commit 80d767d770fd9c697e434fd080c2db7b5c60c6dd upstream.
When compiling for the IA-64 ski emulator, HZ is set to 32 because the
emulation is slow and we don't want to waste too many cycles processing
timers. Alpha also has an option to set HZ to 32.
This causes integer underflow in
kernel/time/jiffies.c:
kernel/time/jiffies.c:66:2: warning: large integer implicitly truncated to unsigned type [-Woverflow]
.mult = NSEC_PER_JIFFY << JIFFIES_SHIFT, /* details above */
^
This patch reduces the JIFFIES_SHIFT value to avoid the overflow.
Signed-off-by: Mikulas Patocka <mikulas@xxxxxxxxxxxxxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/alpine.LRH.2.02.1401241639100.23871@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/time/jiffies.c | 6 ++++++
1 file changed, 6 insertions(+)
--- a/kernel/time/jiffies.c
+++ b/kernel/time/jiffies.c
@@ -51,7 +51,13 @@
* HZ shrinks, so values greater than 8 overflow 32bits when
* HZ=100.
*/
+#if HZ < 34
+#define JIFFIES_SHIFT 6
+#elif HZ < 67
+#define JIFFIES_SHIFT 7
+#else
#define JIFFIES_SHIFT 8
+#endif
static cycle_t jiffies_read(struct clocksource *cs)
{
Patches currently in stable-queue which might be from mpatocka@xxxxxxxxxx are
queue-3.4/time-fix-overflow-when-hz-is-smaller-than-60.patch
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