linux-kernel - [PATCH tip/core/rcu 14/18] rcu: Consolidate expedited CPU selection

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Date:	Tue,  6 Oct 2015 09:29:33 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	linux-kernel@...r.kernel.org
Cc:	mingo@...nel.org, jiangshanlai@...il.com, dipankar@...ibm.com,
	akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
	josh@...htriplett.org, tglx@...utronix.de, peterz@...radead.org,
	rostedt@...dmis.org, dhowells@...hat.com, edumazet@...gle.com,
	dvhart@...ux.intel.com, fweisbec@...il.com, oleg@...hat.com,
	bobby.prani@...il.com,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: [PATCH tip/core/rcu 14/18] rcu: Consolidate expedited CPU selection

Now that sync_sched_exp_select_cpus() and sync_rcu_exp_select_cpus()
are identical aside from the the argument to smp_call_function_single(),
this commit consolidates them with a functional argument.

Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
---
 kernel/rcu/tree.c        |  7 +++---
 kernel/rcu/tree_plugin.h | 61 +-----------------------------------------------
 2 files changed, 5 insertions(+), 63 deletions(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 500b1347554d..ff68087d93a3 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3654,7 +3654,8 @@ static void synchronize_sched_expedited_cpu_stop(void *data)
  * Select the nodes that the upcoming expedited grace period needs
  * to wait for.
  */
-static void sync_sched_exp_select_cpus(struct rcu_state *rsp)
+static void sync_rcu_exp_select_cpus(struct rcu_state *rsp,
+				     smp_call_func_t func)
 {
 	int cpu;
 	unsigned long flags;
@@ -3696,7 +3697,7 @@ static void sync_sched_exp_select_cpus(struct rcu_state *rsp)
 		for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++, mask <<= 1) {
 			if (!(mask_ofl_ipi & mask))
 				continue;
-			ret = smp_call_function_single(cpu, synchronize_sched_expedited_cpu_stop, NULL, 0);
+			ret = smp_call_function_single(cpu, func, rsp, 0);
 			if (!ret)
 				mask_ofl_ipi &= ~mask;
 		}
@@ -3788,7 +3789,7 @@ void synchronize_sched_expedited(void)
 		return;  /* Someone else did our work for us. */
 
 	rcu_exp_gp_seq_start(rsp);
-	sync_sched_exp_select_cpus(rsp);
+	sync_rcu_exp_select_cpus(rsp, synchronize_sched_expedited_cpu_stop);
 	synchronize_sched_expedited_wait(rsp);
 
 	rcu_exp_gp_seq_end(rsp);
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 7880202f1e38..6cbfbfc58656 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -708,65 +708,6 @@ static void sync_rcu_exp_handler(void *info)
 	rcu_report_exp_rdp(rsp, rdp, true);
 }
 
-/*
- * Select the nodes that the upcoming expedited grace period needs
- * to wait for.
- */
-static void sync_rcu_exp_select_cpus(struct rcu_state *rsp)
-{
-	int cpu;
-	unsigned long flags;
-	unsigned long mask;
-	unsigned long mask_ofl_test;
-	unsigned long mask_ofl_ipi;
-	int ret;
-	struct rcu_node *rnp;
-
-	sync_exp_reset_tree(rsp);
-	rcu_for_each_leaf_node(rsp, rnp) {
-		raw_spin_lock_irqsave(&rnp->lock, flags);
-		smp_mb__after_unlock_lock();
-
-		/* Each pass checks a CPU for identity, offline, and idle. */
-		mask_ofl_test = 0;
-		for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++) {
-			struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
-			struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu);
-
-			if (raw_smp_processor_id() == cpu ||
-			    cpu_is_offline(cpu) ||
-			    !(atomic_add_return(0, &rdtp->dynticks) & 0x1))
-				mask_ofl_test |= rdp->grpmask;
-		}
-		mask_ofl_ipi = rnp->expmask & ~mask_ofl_test;
-
-		/*
-		 * Need to wait for any blocked tasks as well.  Note that
-		 * additional blocking tasks will also block the expedited
-		 * GP until such time as the ->expmask bits are cleared.
-		 */
-		if (rcu_preempt_has_tasks(rnp))
-			rnp->exp_tasks = rnp->blkd_tasks.next;
-		raw_spin_unlock_irqrestore(&rnp->lock, flags);
-
-		/* IPI the remaining CPUs for expedited quiescent state. */
-		mask = 1;
-		for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++, mask <<= 1) {
-			if (!(mask_ofl_ipi & mask))
-				continue;
-			ret = smp_call_function_single(cpu,
-						       sync_rcu_exp_handler,
-						       rsp, 0);
-			if (!ret)
-				mask_ofl_ipi &= ~mask;
-		}
-		/* Report quiescent states for those that went offline. */
-		mask_ofl_test |= mask_ofl_ipi;
-		if (mask_ofl_test)
-			rcu_report_exp_cpu_mult(rsp, rnp, mask_ofl_test, false);
-	}
-}
-
 /**
  * synchronize_rcu_expedited - Brute-force RCU grace period
  *
@@ -795,7 +736,7 @@ void synchronize_rcu_expedited(void)
 	rcu_exp_gp_seq_start(rsp);
 
 	/* Initialize the rcu_node tree in preparation for the wait. */
-	sync_rcu_exp_select_cpus(rsp);
+	sync_rcu_exp_select_cpus(rsp, sync_rcu_exp_handler);
 
 	/* Wait for snapshotted ->blkd_tasks lists to drain. */
 	rnp = rcu_get_root(rsp);
-- 
2.5.2

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