From 7386cdbf2f57ea8cff3c9fde93f206e58b9fe13f Mon Sep 17 00:00:00 2001
From: Michal Hocko <mhocko@suse.cz>
Date: Wed, 10 Oct 2012 11:51:09 +0530
Subject: [PATCH 1/2] nohz: Fix idle ticks in cpu summary line of /proc/stat
Git commit 09a1d34f8535ecf9 "nohz: Make idle/iowait counter update
conditional" introduced a bug in regard to cpu hotplug. The effect is
that the number of idle ticks in the cpu summary line in /proc/stat is
still counting ticks for offline cpus.
Reproduction is easy, just start a workload that keeps all cpus busy,
switch off one or more cpus and then watch the idle field in top.
On a dual-core with one cpu 100% busy and one offline cpu you will get
something like this:
%Cpu(s): 48.7 us, 1.3 sy, 0.0 ni, 50.0 id, 0.0 wa, 0.0 hi, 0.0 si,
%0.0 st
The problem is that an offline cpu still has ts->idle_active == 1.
To fix this we should make sure that the cpu is online when calling
get_cpu_idle_time_us and get_cpu_iowait_time_us.
[Srivatsa: Rebased to current mainline]
Reported-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Michal Hocko <mhocko@suse.cz>
Reviewed-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/20121010061820.8999.57245.stgit@srivatsabhat.in.ibm.com
Cc: deepthi@linux.vnet.ibm.com
Cc: stable@vger.kernel.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
fs/proc/stat.c | 14 ++++++++++----
1 file changed, 10 insertions(+), 4 deletions(-)
diff --git a/fs/proc/stat.c b/fs/proc/stat.c
index 64c3b3172367..e296572c73ed 100644
--- a/fs/proc/stat.c
+++ b/fs/proc/stat.c
@@ -45,10 +45,13 @@ static cputime64_t get_iowait_time(int cpu)
static u64 get_idle_time(int cpu)
{
- u64 idle, idle_time = get_cpu_idle_time_us(cpu, NULL);
+ u64 idle, idle_time = -1ULL;
+
+ if (cpu_online(cpu))
+ idle_time = get_cpu_idle_time_us(cpu, NULL);
if (idle_time == -1ULL)
- /* !NO_HZ so we can rely on cpustat.idle */
+ /* !NO_HZ or cpu offline so we can rely on cpustat.idle */
idle = kcpustat_cpu(cpu).cpustat[CPUTIME_IDLE];
else
idle = usecs_to_cputime64(idle_time);
@@ -58,10 +61,13 @@ static u64 get_idle_time(int cpu)
static u64 get_iowait_time(int cpu)
{
- u64 iowait, iowait_time = get_cpu_iowait_time_us(cpu, NULL);
+ u64 iowait, iowait_time = -1ULL;
+
+ if (cpu_online(cpu))
+ iowait_time = get_cpu_iowait_time_us(cpu, NULL);
if (iowait_time == -1ULL)
- /* !NO_HZ so we can rely on cpustat.iowait */
+ /* !NO_HZ or cpu offline so we can rely on cpustat.iowait */
iowait = kcpustat_cpu(cpu).cpustat[CPUTIME_IOWAIT];
else
iowait = usecs_to_cputime64(iowait_time);
From fd0587339d80dd2fea5ead7f734676c9c618eace Mon Sep 17 00:00:00 2001
From: Jean Delvare <khali@linux-fr.org>
Date: Sun, 21 Oct 2012 12:05:51 +0200
Subject: [PATCH 2/2] Documentation: Reflect the new location of the NMI
watchdog info
Commit 9919cba7 ("watchdog: Update documentation") moved the
NMI watchdog documentation from nmi_watchdog.txt to
lockup-watchdogs.txt. Update the index file accordingly.
Signed-off-by: Jean Delvare <khali@linux-fr.org>
Cc: Fernando Luis Vazquez Cao <fernando@oss.ntt.co.jp>
Cc: Randy Dunlap <rdunlap@xenotime.net>
Cc: Don Zickus <dzickus@redhat.com>
Link: http://lkml.kernel.org/r/20121021120551.4656d99b@endymion.delvare
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
Documentation/00-INDEX | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/Documentation/00-INDEX b/Documentation/00-INDEX
index 49c051380daf..fec55dc5ed2f 100644
--- a/Documentation/00-INDEX
+++ b/Documentation/00-INDEX
@@ -210,6 +210,8 @@ local_ops.txt
- semantics and behavior of local atomic operations.
lockdep-design.txt
- documentation on the runtime locking correctness validator.
+lockup-watchdogs.txt
+ - info on soft and hard lockup detectors (aka nmi_watchdog).
logo.gif
- full colour GIF image of Linux logo (penguin - Tux).
logo.txt
@@ -240,8 +242,6 @@ netlabel/
- directory with information on the NetLabel subsystem.
networking/
- directory with info on various aspects of networking with Linux.
-nmi_watchdog.txt
- - info on NMI watchdog for SMP systems.
nommu-mmap.txt
- documentation about no-mmu memory mapping support.
numastat.txt