sched/core: Add missing update_rq_clock() call for task_hot()

Peter Zijlstra · Ingo Molnar · commit 3bed5e2166a5 · 2017-01-14T11:29:34.000+01:00
Add the update_rq_clock() call at the top of the callstack instead of
at the bottom where we find it missing, this to aid later effort to
minimize the number of update_rq_lock() calls.

  WARNING: CPU: 30 PID: 194 at ../kernel/sched/sched.h:797 assert_clock_updated()
  rq-&gt;clock_update_flags &lt; RQCF_ACT_SKIP

  Call Trace:
    dump_stack()
    __warn()
    warn_slowpath_fmt()
    assert_clock_updated.isra.63.part.64()
    can_migrate_task()
    load_balance()
    pick_next_task_fair()
    __schedule()
    schedule()
    worker_thread()
    kthread()

Signed-off-by: Peter Zijlstra (Intel) &lt;peterz@infradead.org&gt;
Cc: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
Cc: Mike Galbraith &lt;efault@gmx.de&gt;
Cc: Peter Zijlstra &lt;peterz@infradead.org&gt;
Cc: Thomas Gleixner &lt;tglx@linutronix.de&gt;
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar &lt;mingo@kernel.org&gt;
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
@@ -8070,6 +8070,7 @@ static int load_balance(int this_cpu, struct rq *this_rq,
 
 more_balance:
 		raw_spin_lock_irqsave(&busiest->lock, flags);
+		update_rq_clock(busiest);
 
 		/*
 		 * cur_ld_moved - load moved in current iteration
@@ -8446,6 +8447,7 @@ static int active_load_balance_cpu_stop(void *data)
 		};
 
 		schedstat_inc(sd->alb_count);
+		update_rq_clock(busiest_rq);
 
 		p = detach_one_task(&env);
 		if (p) {
