Merge branch 'urgent' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu

Pull RCU fixes from Paul McKenney:

 - fix regressions induced by a merge-window change in scheduler
   semantics, which means that smp_processor_id() can no longer be used
   in kthreads using simple affinity to bind themselves to a specific
   CPU.

 - fix a bug in Tasks Trace RCU that was thought to be strictly
   theoretical. However, production workloads have started hitting this,
   so these fixes need to be merged sooner rather than later.

 - fix a minor printk()-format-mismatch issue introduced during the
   merge window.

* 'urgent' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu:
  rcu: Fix pr_info() formats and values in show_rcu_gp_kthreads()
  rcu-tasks: Don't delete holdouts within trc_wait_for_one_reader()
  rcu-tasks: Don't delete holdouts within trc_inspect_reader()
  refscale: Avoid false-positive warnings in ref_scale_reader()
  scftorture: Avoid false-positive warnings in scftorture_invoker()

Author: torvalds

kernel/rcu/refscale.c

@@ -487,13 +487,13 @@ ref_scale_reader(void *arg)
 	s64 duration;
 
 	VERBOSE_SCALEOUT_BATCH("ref_scale_reader %ld: task started", me);
-	set_cpus_allowed_ptr(current, cpumask_of(me % nr_cpu_ids));
+	WARN_ON_ONCE(set_cpus_allowed_ptr(current, cpumask_of(me % nr_cpu_ids)));
 	set_user_nice(current, MAX_NICE);
 	atomic_inc(&n_init);
 	if (holdoff)
 		schedule_timeout_interruptible(holdoff * HZ);
 repeat:
-	VERBOSE_SCALEOUT_BATCH("ref_scale_reader %ld: waiting to start next experiment on cpu %d", me, smp_processor_id());
+	VERBOSE_SCALEOUT_BATCH("ref_scale_reader %ld: waiting to start next experiment on cpu %d", me, raw_smp_processor_id());
 
 	// Wait for signal that this reader can start.
 	wait_event(rt->wq, (atomic_read(&nreaders_exp) && smp_load_acquire(&rt->start_reader)) ||
@@ -503,7 +503,7 @@ ref_scale_reader(void *arg)
 		goto end;
 
 	// Make sure that the CPU is affinitized appropriately during testing.
-	WARN_ON_ONCE(smp_processor_id() != me);
+	WARN_ON_ONCE(raw_smp_processor_id() != me);
 
 	WRITE_ONCE(rt->start_reader, 0);
 	if (!atomic_dec_return(&n_started))

kernel/rcu/tasks.h

@@ -953,10 +953,9 @@ static bool trc_inspect_reader(struct task_struct *t, void *arg)
 		in_qs = likely(!t->trc_reader_nesting);
 	}
 
-	// Mark as checked.  Because this is called from the grace-period
-	// kthread, also remove the task from the holdout list.
+	// Mark as checked so that the grace-period kthread will
+	// remove it from the holdout list.
 	t->trc_reader_checked = true;
-	trc_del_holdout(t);
 
 	if (in_qs)
 		return true;  // Already in quiescent state, done!!!
@@ -983,7 +982,6 @@ static void trc_wait_for_one_reader(struct task_struct *t,
 	// The current task had better be in a quiescent state.
 	if (t == current) {
 		t->trc_reader_checked = true;
-		trc_del_holdout(t);
 		WARN_ON_ONCE(t->trc_reader_nesting);
 		return;
 	}

kernel/rcu/tree_stall.h

@@ -795,9 +795,9 @@ void show_rcu_gp_kthreads(void)
 	jr = j - data_race(rcu_state.gp_req_activity);
 	js = j - data_race(rcu_state.gp_start);
 	jw = j - data_race(rcu_state.gp_wake_time);
-	pr_info("%s: wait state: %s(%d) ->state: %#lx ->rt_priority %u delta ->gp_start %lu ->gp_activity %lu ->gp_req_activity %lu ->gp_wake_time %lu ->gp_wake_seq %ld ->gp_seq %ld ->gp_seq_needed %ld ->gp_max %lu ->gp_flags %#x\n",
+	pr_info("%s: wait state: %s(%d) ->state: %#x ->rt_priority %u delta ->gp_start %lu ->gp_activity %lu ->gp_req_activity %lu ->gp_wake_time %lu ->gp_wake_seq %ld ->gp_seq %ld ->gp_seq_needed %ld ->gp_max %lu ->gp_flags %#x\n",
 		rcu_state.name, gp_state_getname(rcu_state.gp_state),
-		rcu_state.gp_state, t ? t->__state : 0x1ffffL, t ? t->rt_priority : 0xffU,
+		rcu_state.gp_state, t ? t->__state : 0x1ffff, t ? t->rt_priority : 0xffU,
 		js, ja, jr, jw, (long)data_race(rcu_state.gp_wake_seq),
 		(long)data_race(rcu_state.gp_seq),
 		(long)data_race(rcu_get_root()->gp_seq_needed),

kernel/scftorture.c

@@ -405,15 +405,15 @@ static int scftorture_invoker(void *arg)
 
 	VERBOSE_SCFTORTOUT("scftorture_invoker %d: task started", scfp->cpu);
 	cpu = scfp->cpu % nr_cpu_ids;
-	set_cpus_allowed_ptr(current, cpumask_of(cpu));
+	WARN_ON_ONCE(set_cpus_allowed_ptr(current, cpumask_of(cpu)));
 	set_user_nice(current, MAX_NICE);
 	if (holdoff)
 		schedule_timeout_interruptible(holdoff * HZ);
 
-	VERBOSE_SCFTORTOUT("scftorture_invoker %d: Waiting for all SCF torturers from cpu %d", scfp->cpu, smp_processor_id());
+	VERBOSE_SCFTORTOUT("scftorture_invoker %d: Waiting for all SCF torturers from cpu %d", scfp->cpu, raw_smp_processor_id());
 
 	// Make sure that the CPU is affinitized appropriately during testing.
-	curcpu = smp_processor_id();
+	curcpu = raw_smp_processor_id();
 	WARN_ONCE(curcpu != scfp->cpu % nr_cpu_ids,
 		  "%s: Wanted CPU %d, running on %d, nr_cpu_ids = %d\n",
 		  __func__, scfp->cpu, curcpu, nr_cpu_ids);