[ANNOUNCE] v4.18.16-rt9

[Sebastian Andrzej Siewior]

Dear RT folks!

I'm pleased to announce the v4.18.16-rt9 patch set. 

Changes since v4.18.16-rt8:

  - The RCU fix, which was introduced in v4.18.7-rt5, leads to a lockdep
    warning during CPU hotplug. After a discussion with upstream it was
    suggested to revert the change that lead to the problem in -RT.

Known issues
     - A warning triggered in "rcu_note_context_switch" originated from
       SyS_timer_gettime(). The issue was always there, it is now
       visible. Reported by Grygorii Strashko and Daniel Wagner.

The delta patch against v4.18.16-rt8 is appended below and can be found here:
 
     https://cdn.kernel.org/pub/linux/kernel/projects/rt/4.18/incr/patch-4.18.16-rt8-rt9.patch.xz

You can get this release via the git tree at:

    git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git v4.18.16-rt9

The RT patch against v4.18.16 can be found here:

    https://cdn.kernel.org/pub/linux/kernel/projects/rt/4.18/older/patch-4.18.16-rt9.patch.xz

The split quilt queue is available at:

    https://cdn.kernel.org/pub/linux/kernel/projects/rt/4.18/older/patches-4.18.16-rt9.tar.xz

Sebastian

diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h
index a104cf91e6b90..d40708e8c5d6e 100644
--- a/kernel/rcu/tree_exp.h
+++ b/kernel/rcu/tree_exp.h
@@ -472,14 +472,12 @@ static void sync_rcu_exp_select_node_cpus(struct work_struct *wp)
 static void sync_rcu_exp_select_cpus(struct rcu_state *rsp,
 				     smp_call_func_t func)
 {
-	int cpu;
 	struct rcu_node *rnp;
 
 	trace_rcu_exp_grace_period(rsp->name, rcu_exp_gp_seq_endval(rsp), TPS("reset"));
 	sync_exp_reset_tree(rsp);
 	trace_rcu_exp_grace_period(rsp->name, rcu_exp_gp_seq_endval(rsp), TPS("select"));
 
-	cpus_read_lock();
 	/* Schedule work for each leaf rcu_node structure. */
 	rcu_for_each_leaf_node(rsp, rnp) {
 		rnp->exp_need_flush = false;
@@ -494,11 +492,7 @@ static void sync_rcu_exp_select_cpus(struct rcu_state *rsp,
 			continue;
 		}
 		INIT_WORK(&rnp->rew.rew_work, sync_rcu_exp_select_node_cpus);
-		cpu = cpumask_next(rnp->grplo - 1, cpu_online_mask);
-		/* If all offline, queue the work on an unbound CPU. */
-		if (unlikely(cpu > rnp->grphi))
-			cpu = WORK_CPU_UNBOUND;
-		queue_work_on(cpu, rcu_par_gp_wq, &rnp->rew.rew_work);
+		queue_work_on(rnp->grplo, rcu_par_gp_wq, &rnp->rew.rew_work);
 		rnp->exp_need_flush = true;
 	}
 
@@ -506,7 +500,6 @@ static void sync_rcu_exp_select_cpus(struct rcu_state *rsp,
 	rcu_for_each_leaf_node(rsp, rnp)
 		if (rnp->exp_need_flush)
 			flush_work(&rnp->rew.rew_work);
-	cpus_read_unlock();
 }
 
 static void synchronize_sched_expedited_wait(struct rcu_state *rsp)
diff --git a/localversion-rt b/localversion-rt
index 700c857efd9ba..22746d6390a42 100644
--- a/localversion-rt
+++ b/localversion-rt
@@ -1 +1 @@
--rt8
+-rt9