Subject: linux-next: manual merge of the rcu tree with the tip tree

From: Stephen Rothwell <[email-masked]>
Date: Tue, 22 Jun 2021 14:47:57 +1000

Hi all,

Today's linux-next merge of the rcu tree got a conflict in:

  kernel/rcu/tree_stall.h

between commit:

  2f064a59a11f ("sched: Change task_struct::state")

from the tip tree and commit:

  367455053a76 ("rcu: Mark accesses in tree_stall.h")

from the rcu tree.

I fixed it up (see below) and can carry the fix as necessary. This
is now fixed as far as linux-next is concerned, but any non trivial
conflicts should be mentioned to your upstream maintainer when your tree
is submitted for merging.  You may also want to consider cooperating
with the maintainer of the conflicting tree to minimise any particularly
complex conflicts.

-- 
Cheers,
Stephen Rothwell

diff --cc kernel/rcu/tree_stall.h
index acb2288063b5,24065f1acb8b..000000000000
--- a/kernel/rcu/tree_stall.h
+++ b/kernel/rcu/tree_stall.h
@@@ -460,12 -462,13 +462,13 @@@ static void rcu_check_gp_kthread_starva
  
  	if (rcu_is_gp_kthread_starving(&j)) {
  		cpu = gpk ? task_cpu(gpk) : -1;
 -		pr_err("%s kthread starved for %ld jiffies! g%ld f%#x %s(%d) ->state=%#lx ->cpu=%d\n",
 +		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);
++		       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");
@@@ -508,7 -511,7 +511,7 @@@ static void rcu_check_gp_kthread_expire
  		       (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)));
++		       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));
  	}
@@@ -732,23 -816,34 +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);
- 	jw = j - data_race(rcu_state.gp_wake_time);
- 	pr_info("%s: wait state: %s(%d) ->state: %#x delta ->gp_activity %lu ->gp_req_activity %lu ->gp_wake_time %lu ->gp_wake_seq %ld ->gp_seq %ld ->gp_seq_needed %ld ->gp_flags %#x\n",
+ 	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: %#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 : 0x1ffff,
- 		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_flags));
+ 		data_race(READ_ONCE(rcu_state.gp_state)),
 -		t ? data_race(READ_ONCE(t->state)) : 0x1ffffL, t ? t->rt_priority : 0xffU,
++		t ? data_race(READ_ONCE(t->__state)) : 0x1ffffL, 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)))
+ 		if (ULONG_CMP_GE(READ_ONCE(rcu_state.gp_seq), READ_ONCE(rnp->gp_seq_needed)) &&
+ 		    !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\n",
- 			rnp->grplo, rnp->grphi, (long)data_race(rnp->gp_seq),
- 			(long)data_race(rnp->gp_seq_needed));
+ 		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(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) {