Commit d283aa1b authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcu: Mark accesses in tree_stall.h 



This commit marks the accesses in tree_stall.h so as to both avoid
undesirable compiler optimizations and to keep KCSAN focused on the
accesses of the core algorithm.

Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
parent f74126dc

kernel/rcu/tree_stall.h

+33 −30
Original line number Diff line number Diff line
@@ -465,9 +465,10 @@ static void rcu_check_gp_kthread_starvation(void) 
		pr_err("%s kthread starved for %ld jiffies! g%ld f%#x %s(%d) ->state=%#x ->cpu=%d\n",

		       rcu_state.name, j,

		       (long)rcu_seq_current(&rcu_state.gp_seq),

		       data_race(rcu_state.gp_flags),

		       gp_state_getname(rcu_state.gp_state), rcu_state.gp_state,

		       gpk ? gpk->__state : ~0, cpu);

		       data_race(READ_ONCE(rcu_state.gp_flags)),

		       gp_state_getname(rcu_state.gp_state),

		       data_race(READ_ONCE(rcu_state.gp_state)),

		       gpk ? data_race(READ_ONCE(gpk->__state)) : ~0, cpu);

		if (gpk) {

			pr_err("\tUnless %s kthread gets sufficient CPU time, OOM is now expected behavior.\n", rcu_state.name);

			pr_err("RCU grace-period kthread stack dump:\n");
@@ -510,7 +511,7 @@ static void rcu_check_gp_kthread_expired_fqs_timer(void) 
		       (long)rcu_seq_current(&rcu_state.gp_seq),

		       data_race(rcu_state.gp_flags),

		       gp_state_getname(RCU_GP_WAIT_FQS), RCU_GP_WAIT_FQS,

		       gpk->__state);

		       data_race(READ_ONCE(gpk->__state)));

		pr_err("\tPossible timer handling issue on cpu=%d timer-softirq=%u\n",

		       cpu, kstat_softirqs_cpu(TIMER_SOFTIRQ, cpu));

	}
@@ -569,11 +570,11 @@ static void print_other_cpu_stall(unsigned long gp_seq, unsigned long gps) 
			pr_err("INFO: Stall ended before state dump start\n");

		} else {

			j = jiffies;

			gpa = data_race(rcu_state.gp_activity);

			gpa = data_race(READ_ONCE(rcu_state.gp_activity));

			pr_err("All QSes seen, last %s kthread activity %ld (%ld-%ld), jiffies_till_next_fqs=%ld, root ->qsmask %#lx\n",

			       rcu_state.name, j - gpa, j, gpa,

			       data_race(jiffies_till_next_fqs),

			       rcu_get_root()->qsmask);

			       data_race(READ_ONCE(jiffies_till_next_fqs)),

			       data_race(READ_ONCE(rcu_get_root()->qsmask)));

		}

	}

	/* Rewrite if needed in case of slow consoles. */
@@ -815,32 +816,34 @@ void show_rcu_gp_kthreads(void) 
	struct task_struct *t = READ_ONCE(rcu_state.gp_kthread);



	j = jiffies;

	ja = j - data_race(rcu_state.gp_activity);

	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);

	ja = j - data_race(READ_ONCE(rcu_state.gp_activity));

	jr = j - data_race(READ_ONCE(rcu_state.gp_req_activity));

	js = j - data_race(READ_ONCE(rcu_state.gp_start));

	jw = j - data_race(READ_ONCE(rcu_state.gp_wake_time));

	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 : 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),

		data_race(rcu_state.gp_max),

		data_race(rcu_state.gp_flags));

		data_race(READ_ONCE(rcu_state.gp_state)),

		t ? data_race(READ_ONCE(t->__state)) : 0x1ffff, t ? t->rt_priority : 0xffU,

		js, ja, jr, jw, (long)data_race(READ_ONCE(rcu_state.gp_wake_seq)),

		(long)data_race(READ_ONCE(rcu_state.gp_seq)),

		(long)data_race(READ_ONCE(rcu_get_root()->gp_seq_needed)),

		data_race(READ_ONCE(rcu_state.gp_max)),

		data_race(READ_ONCE(rcu_state.gp_flags)));

	rcu_for_each_node_breadth_first(rnp) {

		if (ULONG_CMP_GE(READ_ONCE(rcu_state.gp_seq), READ_ONCE(rnp->gp_seq_needed)) &&

		    !data_race(rnp->qsmask) && !data_race(rnp->boost_tasks) &&

		    !data_race(rnp->exp_tasks) && !data_race(rnp->gp_tasks))

		    !data_race(READ_ONCE(rnp->qsmask)) && !data_race(READ_ONCE(rnp->boost_tasks)) &&

		    !data_race(READ_ONCE(rnp->exp_tasks)) && !data_race(READ_ONCE(rnp->gp_tasks)))

			continue;

		pr_info("\trcu_node %d:%d ->gp_seq %ld ->gp_seq_needed %ld ->qsmask %#lx %c%c%c%c ->n_boosts %ld\n",

			rnp->grplo, rnp->grphi,

			(long)data_race(rnp->gp_seq), (long)data_race(rnp->gp_seq_needed),

			data_race(rnp->qsmask),

			".b"[!!data_race(rnp->boost_kthread_task)],

			".B"[!!data_race(rnp->boost_tasks)],

			".E"[!!data_race(rnp->exp_tasks)],

			".G"[!!data_race(rnp->gp_tasks)],

			data_race(rnp->n_boosts));

			(long)data_race(READ_ONCE(rnp->gp_seq)),

			(long)data_race(READ_ONCE(rnp->gp_seq_needed)),

			data_race(READ_ONCE(rnp->qsmask)),

			".b"[!!data_race(READ_ONCE(rnp->boost_kthread_task))],

			".B"[!!data_race(READ_ONCE(rnp->boost_tasks))],

			".E"[!!data_race(READ_ONCE(rnp->exp_tasks))],

			".G"[!!data_race(READ_ONCE(rnp->gp_tasks))],

			data_race(READ_ONCE(rnp->n_boosts)));

		if (!rcu_is_leaf_node(rnp))

			continue;

		for_each_leaf_node_possible_cpu(rnp, cpu) {
@@ -850,12 +853,12 @@ void show_rcu_gp_kthreads(void) 
					 READ_ONCE(rdp->gp_seq_needed)))

				continue;

			pr_info("\tcpu %d ->gp_seq_needed %ld\n",

				cpu, (long)data_race(rdp->gp_seq_needed));

				cpu, (long)data_race(READ_ONCE(rdp->gp_seq_needed)));

		}

	}

	for_each_possible_cpu(cpu) {

		rdp = per_cpu_ptr(&rcu_data, cpu);

		cbs += data_race(rdp->n_cbs_invoked);

		cbs += data_race(READ_ONCE(rdp->n_cbs_invoked));

		if (rcu_segcblist_is_offloaded(&rdp->cblist))

			show_rcu_nocb_state(rdp);

	}
@@ -937,11 +940,11 @@ void rcu_fwd_progress_check(unsigned long j) 


	if (rcu_gp_in_progress()) {

		pr_info("%s: GP age %lu jiffies\n",

			__func__, jiffies - rcu_state.gp_start);

			__func__, jiffies - data_race(READ_ONCE(rcu_state.gp_start)));

		show_rcu_gp_kthreads();

	} else {

		pr_info("%s: Last GP end %lu jiffies ago\n",

			__func__, jiffies - rcu_state.gp_end);

			__func__, jiffies - data_race(READ_ONCE(rcu_state.gp_end)));

		preempt_disable();

		rdp = this_cpu_ptr(&rcu_data);

		rcu_check_gp_start_stall(rdp->mynode, rdp, j);