From: Mikulas Patocka Date: Fri, 24 Jan 2014 21:41:36 +0000 (-0500) Subject: time: Fix overflow when HZ is smaller than 60 X-Git-Tag: v3.4.82~4 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=d6e20e8145341ed1b5d605a8d9ab8463b0ca6ed8;p=platform%2Fkernel%2Flinux-stable.git time: Fix overflow when HZ is smaller than 60 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 Link: http://lkml.kernel.org/r/alpine.LRH.2.02.1401241639100.23871@file01.intranet.prod.int.rdu2.redhat.com Signed-off-by: Thomas Gleixner Signed-off-by: Greg Kroah-Hartman --- diff --git a/kernel/time/jiffies.c b/kernel/time/jiffies.c index a470154..955560e 100644 --- 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) {