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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
parents390/time: fix get_tod_clock_ext inline assembly (diff)
downloadlinux-4560e7c3317c7a2b370e36dadd3a3bac2ed70818.tar.xz
linux-4560e7c3317c7a2b370e36dadd3a3bac2ed70818.zip
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>
-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;
}