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authorThomas Gleixner <tglx@linutronix.de>2016-07-12 16:33:56 (GMT)
committerIngo Molnar <mingo@kernel.org>2016-07-13 12:58:20 (GMT)
commitd60585c5766e9620d5d83e2b25dc042c7bdada2c (patch)
treeace0971cf7c7dcab339997d82ed635b8486dcb28
parent92d21ac74a9e3c09b0b01c764e530657e4c85c49 (diff)
downloadlinux-d60585c5766e9620d5d83e2b25dc042c7bdada2c.tar.xz
sched/core: Correct off by one bug in load migration calculation
The move of calc_load_migrate() from CPU_DEAD to CPU_DYING did not take into account that the function is now called from a thread running on the outgoing CPU. As a result a cpu unplug leakes a load of 1 into the global load accounting mechanism. Fix it by adjusting for the currently running thread which calls calc_load_migrate(). Reported-by: Anton Blanchard <anton@samba.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com> Cc: rt@linutronix.de Cc: shreyas@linux.vnet.ibm.com Fixes: e9cd8fa4fcfd: ("sched/migration: Move calc_load_migrate() into CPU_DYING") Link: http://lkml.kernel.org/r/alpine.DEB.2.11.1607121744350.4083@nanos Signed-off-by: Ingo Molnar <mingo@kernel.org>
-rw-r--r--kernel/sched/core.c6
-rw-r--r--kernel/sched/loadavg.c8
-rw-r--r--kernel/sched/sched.h2
3 files changed, 9 insertions, 7 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 51d7105..97ee9ac 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5394,13 +5394,15 @@ void idle_task_exit(void)
/*
* Since this CPU is going 'away' for a while, fold any nr_active delta
* we might have. Assumes we're called after migrate_tasks() so that the
- * nr_active count is stable.
+ * nr_active count is stable. We need to take the teardown thread which
+ * is calling this into account, so we hand in adjust = 1 to the load
+ * calculation.
*
* Also see the comment "Global load-average calculations".
*/
static void calc_load_migrate(struct rq *rq)
{
- long delta = calc_load_fold_active(rq);
+ long delta = calc_load_fold_active(rq, 1);
if (delta)
atomic_long_add(delta, &calc_load_tasks);
}
diff --git a/kernel/sched/loadavg.c b/kernel/sched/loadavg.c
index b0b93fd..a2d6eb7 100644
--- a/kernel/sched/loadavg.c
+++ b/kernel/sched/loadavg.c
@@ -78,11 +78,11 @@ void get_avenrun(unsigned long *loads, unsigned long offset, int shift)
loads[2] = (avenrun[2] + offset) << shift;
}
-long calc_load_fold_active(struct rq *this_rq)
+long calc_load_fold_active(struct rq *this_rq, long adjust)
{
long nr_active, delta = 0;
- nr_active = this_rq->nr_running;
+ nr_active = this_rq->nr_running - adjust;
nr_active += (long)this_rq->nr_uninterruptible;
if (nr_active != this_rq->calc_load_active) {
@@ -188,7 +188,7 @@ void calc_load_enter_idle(void)
* We're going into NOHZ mode, if there's any pending delta, fold it
* into the pending idle delta.
*/
- delta = calc_load_fold_active(this_rq);
+ delta = calc_load_fold_active(this_rq, 0);
if (delta) {
int idx = calc_load_write_idx();
@@ -389,7 +389,7 @@ void calc_global_load_tick(struct rq *this_rq)
if (time_before(jiffies, this_rq->calc_load_update))
return;
- delta = calc_load_fold_active(this_rq);
+ delta = calc_load_fold_active(this_rq, 0);
if (delta)
atomic_long_add(delta, &calc_load_tasks);
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 7cbeb92..898c0d2 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -28,7 +28,7 @@ extern unsigned long calc_load_update;
extern atomic_long_t calc_load_tasks;
extern void calc_global_load_tick(struct rq *this_rq);
-extern long calc_load_fold_active(struct rq *this_rq);
+extern long calc_load_fold_active(struct rq *this_rq, long adjust);
#ifdef CONFIG_SMP
extern void cpu_load_update_active(struct rq *this_rq);