From 00c5535698d5db83a3cd15d7f6a9b95c71044b4d Mon Sep 17 00:00:00 2001 From: Martin Schwidefsky Date: Mon, 28 Oct 2013 12:15:32 +0100 Subject: s390/vtime: correct idle time calculation commit 4560e7c3317c7a2b370e36dadd3a3bac2ed70818 upstream. 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. Signed-off-by: Martin Schwidefsky Signed-off-by: Greg Kroah-Hartman --- arch/s390/kernel/smp.c | 4 ++-- arch/s390/kernel/vtime.c | 2 +- 2 files changed, 3 insertions(+), 3 deletions(-) (limited to 'arch') diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c index 1a4313a1b60..93439cd0440 100644 --- a/arch/s390/kernel/smp.c +++ b/arch/s390/kernel/smp.c @@ -929,7 +929,7 @@ 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); @@ -947,7 +947,7 @@ 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 abcfab55f99..bb06a76040b 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; } -- cgit v1.2.3-18-g5258