Commit 4560e7c3 authored by Martin Schwidefsky's avatar Martin Schwidefsky

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: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent 7ab64a85
...@@ -920,7 +920,7 @@ static ssize_t show_idle_count(struct device *dev, ...@@ -920,7 +920,7 @@ static ssize_t show_idle_count(struct device *dev,
idle_count = ACCESS_ONCE(idle->idle_count); idle_count = ACCESS_ONCE(idle->idle_count);
if (ACCESS_ONCE(idle->clock_idle_enter)) if (ACCESS_ONCE(idle->clock_idle_enter))
idle_count++; idle_count++;
} while ((sequence & 1) || (idle->sequence != sequence)); } while ((sequence & 1) || (ACCESS_ONCE(idle->sequence) != sequence));
return sprintf(buf, "%llu\n", idle_count); return sprintf(buf, "%llu\n", idle_count);
} }
static DEVICE_ATTR(idle_count, 0444, show_idle_count, NULL); static DEVICE_ATTR(idle_count, 0444, show_idle_count, NULL);
...@@ -938,7 +938,7 @@ static ssize_t show_idle_time(struct device *dev, ...@@ -938,7 +938,7 @@ static ssize_t show_idle_time(struct device *dev,
idle_time = ACCESS_ONCE(idle->idle_time); idle_time = ACCESS_ONCE(idle->idle_time);
idle_enter = ACCESS_ONCE(idle->clock_idle_enter); idle_enter = ACCESS_ONCE(idle->clock_idle_enter);
idle_exit = ACCESS_ONCE(idle->clock_idle_exit); 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; idle_time += idle_enter ? ((idle_exit ? : now) - idle_enter) : 0;
return sprintf(buf, "%llu\n", idle_time >> 12); return sprintf(buf, "%llu\n", idle_time >> 12);
} }
......
...@@ -191,7 +191,7 @@ cputime64_t s390_get_idle_time(int cpu) ...@@ -191,7 +191,7 @@ cputime64_t s390_get_idle_time(int cpu)
sequence = ACCESS_ONCE(idle->sequence); sequence = ACCESS_ONCE(idle->sequence);
idle_enter = ACCESS_ONCE(idle->clock_idle_enter); idle_enter = ACCESS_ONCE(idle->clock_idle_enter);
idle_exit = ACCESS_ONCE(idle->clock_idle_exit); 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; return idle_enter ? ((idle_exit ?: now) - idle_enter) : 0;
} }
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment