Commit 80d767d7 authored by Mikulas Patocka's avatar Mikulas Patocka Committed by Thomas Gleixner

time: Fix overflow when HZ is smaller than 60

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: default avatarMikulas Patocka <mikulas@artax.karlin.mff.cuni.cz>
Link: http://lkml.kernel.org/r/alpine.LRH.2.02.1401241639100.23871@file01.intranet.prod.int.rdu2.redhat.com
Cc: stable@vger.kernel.org
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 38dbfb59
...@@ -51,7 +51,13 @@ ...@@ -51,7 +51,13 @@
* HZ shrinks, so values greater than 8 overflow 32bits when * HZ shrinks, so values greater than 8 overflow 32bits when
* HZ=100. * HZ=100.
*/ */
#if HZ < 34
#define JIFFIES_SHIFT 6
#elif HZ < 67
#define JIFFIES_SHIFT 7
#else
#define JIFFIES_SHIFT 8 #define JIFFIES_SHIFT 8
#endif
static cycle_t jiffies_read(struct clocksource *cs) static cycle_t jiffies_read(struct clocksource *cs)
{ {
......
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