Commit 5ae0f1b5 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcu: Create and use an rcu_rdp_cpu_online() 



The pattern "rdp->grpmask & rcu_rnp_online_cpus(rnp)" occurs frequently
in RCU code in order to determine whether rdp->cpu is online from an
RCU perspective.  This commit therefore creates an rcu_rdp_cpu_online()
function to replace it.

[ paulmck: Apply kernel test robot unused-variable feedback. ]

Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
parent 80b3fd47

kernel/rcu/tree.c

+13 −8
Original line number Diff line number Diff line
@@ -222,6 +222,16 @@ static unsigned long rcu_rnp_online_cpus(struct rcu_node *rnp) 
	return READ_ONCE(rnp->qsmaskinitnext);

}



/*

 * Is the CPU corresponding to the specified rcu_data structure online

 * from RCU's perspective?  This perspective is given by that structure's

 * ->qsmaskinitnext field rather than by the global cpu_online_mask.

 */

static bool rcu_rdp_cpu_online(struct rcu_data *rdp)

{

	return !!(rdp->grpmask & rcu_rnp_online_cpus(rdp->mynode));

}



/*

 * Return true if an RCU grace period is in progress.  The READ_ONCE()s

 * permit this function to be invoked without holding the root rcu_node
@@ -1168,14 +1178,12 @@ void rcu_request_urgent_qs_task(struct task_struct *t) 
bool rcu_lockdep_current_cpu_online(void)

{

	struct rcu_data *rdp;

	struct rcu_node *rnp;

	bool ret = false;



	if (in_nmi() || !rcu_scheduler_fully_active)

		return true;

	preempt_disable_notrace();

	rdp = this_cpu_ptr(&rcu_data);

	rnp = rdp->mynode;

	/*

	 * Strictly, we care here about the case where the current CPU is

	 * in rcu_cpu_starting() and thus has an excuse for rdp->grpmask
@@ -1183,8 +1191,7 @@ bool rcu_lockdep_current_cpu_online(void) 
	 * false positive if it's held by some *other* CPU, but that's

	 * OK because that just means a false *negative* on the warning.

	 */

	if (rdp->grpmask & rcu_rnp_online_cpus(rnp) ||

	    arch_spin_is_locked(&rcu_state.ofl_lock))

	if (rcu_rdp_cpu_online(rdp) || arch_spin_is_locked(&rcu_state.ofl_lock))

		ret = true;

	preempt_enable_notrace();

	return ret;
@@ -1269,8 +1276,7 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) 
	 * For more detail, please refer to the "Hotplug CPU" section

	 * of RCU's Requirements documentation.

	 */

	if (WARN_ON_ONCE(!(rdp->grpmask & rcu_rnp_online_cpus(rnp)))) {

		bool onl;

	if (WARN_ON_ONCE(!rcu_rdp_cpu_online(rdp))) {

		struct rcu_node *rnp1;



		pr_info("%s: grp: %d-%d level: %d ->gp_seq %ld ->completedqs %ld\n",
@@ -1279,9 +1285,8 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) 
		for (rnp1 = rnp; rnp1; rnp1 = rnp1->parent)

			pr_info("%s: %d:%d ->qsmask %#lx ->qsmaskinit %#lx ->qsmaskinitnext %#lx ->rcu_gp_init_mask %#lx\n",

				__func__, rnp1->grplo, rnp1->grphi, rnp1->qsmask, rnp1->qsmaskinit, rnp1->qsmaskinitnext, rnp1->rcu_gp_init_mask);

		onl = !!(rdp->grpmask & rcu_rnp_online_cpus(rnp));

		pr_info("%s %d: %c online: %ld(%d) offline: %ld(%d)\n",

			__func__, rdp->cpu, ".o"[onl],

			__func__, rdp->cpu, ".o"[rcu_rdp_cpu_online(rdp)],

			(long)rdp->rcu_onl_gp_seq, rdp->rcu_onl_gp_flags,

			(long)rdp->rcu_ofl_gp_seq, rdp->rcu_ofl_gp_flags);

		return 1; /* Break things loose after complaining. */

kernel/rcu/tree_plugin.h

+2 −4
Original line number Diff line number Diff line
@@ -330,7 +330,7 @@ void rcu_note_context_switch(bool preempt) 
		 * then queue the task as required based on the states

		 * of any ongoing and expedited grace periods.

		 */

		WARN_ON_ONCE((rdp->grpmask & rcu_rnp_online_cpus(rnp)) == 0);

		WARN_ON_ONCE(!rcu_rdp_cpu_online(rdp));

		WARN_ON_ONCE(!list_empty(&t->rcu_node_entry));

		trace_rcu_preempt_task(rcu_state.name,

				       t->pid,
@@ -773,7 +773,6 @@ dump_blkd_tasks(struct rcu_node *rnp, int ncheck) 
	int cpu;

	int i;

	struct list_head *lhp;

	bool onl;

	struct rcu_data *rdp;

	struct rcu_node *rnp1;
@@ -797,9 +796,8 @@ dump_blkd_tasks(struct rcu_node *rnp, int ncheck) 
	pr_cont("\n");

	for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++) {

		rdp = per_cpu_ptr(&rcu_data, cpu);

		onl = !!(rdp->grpmask & rcu_rnp_online_cpus(rnp));

		pr_info("\t%d: %c online: %ld(%d) offline: %ld(%d)\n",

			cpu, ".o"[onl],

			cpu, ".o"[rcu_rdp_cpu_online(rdp)],

			(long)rdp->rcu_onl_gp_seq, rdp->rcu_onl_gp_flags,

			(long)rdp->rcu_ofl_gp_seq, rdp->rcu_ofl_gp_flags);

	}