Commit 6e442d06 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

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()
parents d936eb23 2a2ed561

kernel/rcu/refscale.c

+3 −3
Original line number Diff line number Diff line
@@ -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

+2 −4
Original line number Diff line number Diff line
@@ -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

+2 −2
Original line number Diff line number Diff line
@@ -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

+3 −3
Original line number Diff line number Diff line
@@ -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);