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authorMartin Schwidefsky <schwidefsky@de.ibm.com>2013-10-28 12:15:32 +0100
committerMartin Schwidefsky <schwidefsky@de.ibm.com>2013-10-31 09:52:52 +0100
commit4560e7c3317c7a2b370e36dadd3a3bac2ed70818 (patch)
treeb0fd4d8705f388783dd893a472105013b702991d /arch/s390
parent7ab64a85e1a009046f97413a573e83fd85f7804d (diff)
downloadlinux-linaro-stable-4560e7c3317c7a2b370e36dadd3a3bac2ed70818.tar.gz
s390/vtime: correct idle time calculation
Use the ACCESS_ONCE macro for both accesses to idle->sequence in the loops to calculate the idle time. If only one access uses the macro, the compiler is free to cache the value for the second access which can cause endless loops. Cc: stable@vger.kernel.org # 3.6+ Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Diffstat (limited to 'arch/s390')
-rw-r--r--arch/s390/kernel/smp.c4
-rw-r--r--arch/s390/kernel/vtime.c2
2 files changed, 3 insertions, 3 deletions
diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
index 739313db71e5..dc4a53465060 100644
--- a/arch/s390/kernel/smp.c
+++ b/arch/s390/kernel/smp.c
@@ -920,7 +920,7 @@ static ssize_t show_idle_count(struct device *dev,
idle_count = ACCESS_ONCE(idle->idle_count);
if (ACCESS_ONCE(idle->clock_idle_enter))
idle_count++;
- } while ((sequence & 1) || (idle->sequence != sequence));
+ } while ((sequence & 1) || (ACCESS_ONCE(idle->sequence) != sequence));
return sprintf(buf, "%llu\n", idle_count);
}
static DEVICE_ATTR(idle_count, 0444, show_idle_count, NULL);
@@ -938,7 +938,7 @@ static ssize_t show_idle_time(struct device *dev,
idle_time = ACCESS_ONCE(idle->idle_time);
idle_enter = ACCESS_ONCE(idle->clock_idle_enter);
idle_exit = ACCESS_ONCE(idle->clock_idle_exit);
- } while ((sequence & 1) || (idle->sequence != sequence));
+ } while ((sequence & 1) || (ACCESS_ONCE(idle->sequence) != sequence));
idle_time += idle_enter ? ((idle_exit ? : now) - idle_enter) : 0;
return sprintf(buf, "%llu\n", idle_time >> 12);
}
diff --git a/arch/s390/kernel/vtime.c b/arch/s390/kernel/vtime.c
index e312c48a1c40..8c34363d6f1e 100644
--- a/arch/s390/kernel/vtime.c
+++ b/arch/s390/kernel/vtime.c
@@ -191,7 +191,7 @@ cputime64_t s390_get_idle_time(int cpu)
sequence = ACCESS_ONCE(idle->sequence);
idle_enter = ACCESS_ONCE(idle->clock_idle_enter);
idle_exit = ACCESS_ONCE(idle->clock_idle_exit);
- } while ((sequence & 1) || (idle->sequence != sequence));
+ } while ((sequence & 1) || (ACCESS_ONCE(idle->sequence) != sequence));
return idle_enter ? ((idle_exit ?: now) - idle_enter) : 0;
}