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Commit 97c668b8 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcu: Rename qs_pending to core_needs_qs 



An upcoming commit needs to invert the sense of the ->passed_quiesce
rcu_data structure field, so this commit is taking this opportunity
to clarify things a bit by renaming ->qs_pending to ->core_needs_qs.

So if !rdp->core_needs_qs, then this CPU need not concern itself with
quiescent states, in particular, it need not acquire its leaf rcu_node
structure's ->lock to check.  Otherwise, it needs to report the next
quiescent state.

Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent bce5fa12

kernel/rcu/tree.c

+7 −7
Original line number Diff line number Diff line
@@ -1746,7 +1746,7 @@ static bool __note_gp_changes(struct rcu_state *rsp, struct rcu_node *rnp, 
		trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("cpustart"));

		rdp->passed_quiesce = 0;

		rdp->rcu_qs_ctr_snap = __this_cpu_read(rcu_qs_ctr);

		rdp->qs_pending = !!(rnp->qsmask & rdp->grpmask);

		rdp->core_needs_qs = !!(rnp->qsmask & rdp->grpmask);

		zero_cpu_stall_ticks(rdp);

		WRITE_ONCE(rdp->gpwrap, false);

	}
@@ -2357,7 +2357,7 @@ rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp) 
	if ((rnp->qsmask & mask) == 0) {

		raw_spin_unlock_irqrestore(&rnp->lock, flags);

	} else {

		rdp->qs_pending = 0;

		rdp->core_needs_qs = 0;



		/*

		 * This GP can't end until cpu checks in, so all of our
@@ -2388,7 +2388,7 @@ rcu_check_quiescent_state(struct rcu_state *rsp, struct rcu_data *rdp) 
	 * Does this CPU still need to do its part for current grace period?

	 * If no, return and let the other CPUs do their part as well.

	 */

	if (!rdp->qs_pending)

	if (!rdp->core_needs_qs)

		return;



	/*
@@ -3828,10 +3828,10 @@ static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp) 


	/* Is the RCU core waiting for a quiescent state from this CPU? */

	if (rcu_scheduler_fully_active &&

	    rdp->qs_pending && !rdp->passed_quiesce &&

	    rdp->core_needs_qs && !rdp->passed_quiesce &&

	    rdp->rcu_qs_ctr_snap == __this_cpu_read(rcu_qs_ctr)) {

		rdp->n_rp_qs_pending++;

	} else if (rdp->qs_pending &&

		rdp->n_rp_core_needs_qs++;

	} else if (rdp->core_needs_qs &&

		   (rdp->passed_quiesce ||

		    rdp->rcu_qs_ctr_snap != __this_cpu_read(rcu_qs_ctr))) {

		rdp->n_rp_report_qs++;
@@ -4157,7 +4157,7 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp) 
	rdp->completed = rnp->completed;

	rdp->passed_quiesce = false;

	rdp->rcu_qs_ctr_snap = per_cpu(rcu_qs_ctr, cpu);

	rdp->qs_pending = false;

	rdp->core_needs_qs = false;

	trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("cpuonl"));

	raw_spin_unlock_irqrestore(&rnp->lock, flags);

}

kernel/rcu/tree.h

+2 −2
Original line number Diff line number Diff line
@@ -303,7 +303,7 @@ struct rcu_data { 
	unsigned long	rcu_qs_ctr_snap;/* Snapshot of rcu_qs_ctr to check */

					/*  for rcu_all_qs() invocations. */

	bool		passed_quiesce;	/* User-mode/idle loop etc. */

	bool		qs_pending;	/* Core waits for quiesc state. */

	bool		core_needs_qs;	/* Core waits for quiesc state. */

	bool		beenonline;	/* CPU online at least once. */

	bool		gpwrap;		/* Possible gpnum/completed wrap. */

	struct rcu_node *mynode;	/* This CPU's leaf of hierarchy */
@@ -368,7 +368,7 @@ struct rcu_data { 


	/* 5) __rcu_pending() statistics. */

	unsigned long n_rcu_pending;	/* rcu_pending() calls since boot. */

	unsigned long n_rp_qs_pending;

	unsigned long n_rp_core_needs_qs;

	unsigned long n_rp_report_qs;

	unsigned long n_rp_cb_ready;

	unsigned long n_rp_cpu_needs_gp;

kernel/rcu/tree_plugin.h

+1 −1
Original line number Diff line number Diff line
@@ -619,7 +619,7 @@ static void rcu_preempt_check_callbacks(void) 
		return;

	}

	if (t->rcu_read_lock_nesting > 0 &&

	    __this_cpu_read(rcu_data_p->qs_pending) &&

	    __this_cpu_read(rcu_data_p->core_needs_qs) &&

	    !__this_cpu_read(rcu_data_p->passed_quiesce))

		t->rcu_read_unlock_special.b.need_qs = true;

}

kernel/rcu/tree_trace.c

+2 −2
Original line number Diff line number Diff line
@@ -123,7 +123,7 @@ static void print_one_rcu_data(struct seq_file *m, struct rcu_data *rdp) 
		   ulong2long(rdp->completed), ulong2long(rdp->gpnum),

		   rdp->passed_quiesce,

		   rdp->rcu_qs_ctr_snap == per_cpu(rcu_qs_ctr, rdp->cpu),

		   rdp->qs_pending);

		   rdp->core_needs_qs);

	seq_printf(m, " dt=%d/%llx/%d df=%lu",

		   atomic_read(&rdp->dynticks->dynticks),

		   rdp->dynticks->dynticks_nesting,
@@ -361,7 +361,7 @@ static void print_one_rcu_pending(struct seq_file *m, struct rcu_data *rdp) 
		   cpu_is_offline(rdp->cpu) ? '!' : ' ',

		   rdp->n_rcu_pending);

	seq_printf(m, "qsp=%ld rpq=%ld cbr=%ld cng=%ld ",

		   rdp->n_rp_qs_pending,

		   rdp->n_rp_core_needs_qs,

		   rdp->n_rp_report_qs,

		   rdp->n_rp_cb_ready,

		   rdp->n_rp_cpu_needs_gp);