move_tasks() and active_load_balance_cpu_stop() both need
to have the busiest rq clock uptodate because they may end
up calling can_migrate_task() that uses rq->clock_task
to determine if the task running in the busiest runqueue
is cache hot.
Hence if the busiest runqueue is tickless, update its clock
before reading it.
Signed-off-by: Frederic Weisbecker <fweis...@gmail.com>
Cc: Alessio Igor Bogani <abog...@kernel.org>
Cc: Andrew Morton <a...@linux-foundation.org>
Cc: Chris Metcalf <cmetc...@tilera.com>
Cc: Christoph Lameter <c...@linux.com>
Cc: Geoff Levand <ge...@infradead.org>
Cc: Gilad Ben Yossef <gi...@benyossef.com>
Cc: Hakan Akkan <hakanak...@gmail.com>
Cc: Ingo Molnar <mi...@kernel.org>
Cc: Paul E. McKenney <paul...@linux.vnet.ibm.com>
Cc: Paul Gortmaker <paul.gortma...@windriver.com>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Steven Rostedt <rost...@goodmis.org>
Cc: Thomas Gleixner <t...@linutronix.de>
[ Forward port conflicts ]
Signed-off-by: Steven Rostedt <rost...@goodmis.org>
---
kernel/sched/fair.c | 17 +++++++++++++++++
1 files changed, 17 insertions(+), 0 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 3d65ac7..e78d81104 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5002,6 +5002,7 @@ static int load_balance(int this_cpu, struct rq *this_rq,
{
int ld_moved, cur_ld_moved, active_balance = 0;
int lb_iterations, max_lb_iterations;
+ int clock_updated;
struct sched_group *group;
struct rq *busiest;
unsigned long flags;
@@ -5045,6 +5046,7 @@ redo:
ld_moved = 0;
lb_iterations = 1;
+ clock_updated = 0;
if (busiest->nr_running > 1) {
/*
* Attempt to move tasks. If find_busiest_group has found
@@ -5068,6 +5070,14 @@ more_balance:
*/
cur_ld_moved = move_tasks(&env);
ld_moved += cur_ld_moved;
+
+ /*
+ * Move tasks may end up calling can_migrate_task() which
+ * requires an uptodate value of the rq clock.
+ */
+ update_nohz_rq_clock(busiest);
+ clock_updated = 1;
+
double_rq_unlock(env.dst_rq, busiest);
local_irq_restore(flags);
@@ -5163,6 +5173,13 @@ more_balance:
busiest->active_balance = 1;
busiest->push_cpu = this_cpu;
active_balance = 1;
+ /*
+ * active_load_balance_cpu_stop may end up
calling
+ * can_migrate_task() which requires an uptodate
+ * value of the rq clock.
+ */
+ if (!clock_updated)
+ update_nohz_rq_clock(busiest);
}
raw_spin_unlock_irqrestore(&busiest->lock, flags);
--
1.7.5.4
--
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