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Commit 560d4bc0 authored by Paul E. McKenney's avatar Paul E. McKenney Committed by Ingo Molnar
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rcu: Further cleanups of use of lastcomp 



Now that a copy of the rsp->completed flag is available in all
rcu_node structures, make full use of it.  It is still
legitimate to access rsp->completed while holding the root
rcu_node structure's lock, however.

Also, tighten up force_quiescent_state()'s checks for end of
current grace period.

Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: mathieu.desnoyers@polymtl.ca
Cc: josh@joshtriplett.org
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: Valdis.Kletnieks@vt.edu
Cc: dhowells@redhat.com
LKML-Reference: <1258170699933-git-send-email->
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 8e9aa8f0

kernel/rcutree.c

+6 −7
Original line number Original line Diff line number Diff line
@@ -817,7 +817,7 @@ cpu_quiet(int cpu, struct rcu_state *rsp, struct rcu_data *rdp, long lastcomp) 




	rnp = rdp->mynode;

	rnp = rdp->mynode;

	spin_lock_irqsave(&rnp->lock, flags);

	spin_lock_irqsave(&rnp->lock, flags);

	if (lastcomp != ACCESS_ONCE(rsp->completed)) {

	if (lastcomp != rnp->completed) {





		/*

		/*

		 * Someone beat us to it for this grace period, so leave.

		 * Someone beat us to it for this grace period, so leave.
@@ -935,7 +935,6 @@ static void rcu_adopt_orphan_cbs(struct rcu_state *rsp) 
static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp)

static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp)

{

{

	unsigned long flags;

	unsigned long flags;

	long lastcomp;

	unsigned long mask;

	unsigned long mask;

	struct rcu_data *rdp = rsp->rda[cpu];

	struct rcu_data *rdp = rsp->rda[cpu];

	struct rcu_node *rnp;

	struct rcu_node *rnp;
@@ -971,7 +970,6 @@ static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp) 
		spin_unlock(&rnp->lock);	/* irqs remain disabled. */

		spin_unlock(&rnp->lock);	/* irqs remain disabled. */

		rnp = rnp->parent;

		rnp = rnp->parent;

	} while (rnp != NULL);

	} while (rnp != NULL);

	lastcomp = rsp->completed;





	spin_unlock_irqrestore(&rsp->onofflock, flags);

	spin_unlock_irqrestore(&rsp->onofflock, flags);
@@ -1145,7 +1143,7 @@ static int rcu_process_dyntick(struct rcu_state *rsp, long lastcomp, 
	rcu_for_each_leaf_node(rsp, rnp) {

	rcu_for_each_leaf_node(rsp, rnp) {

		mask = 0;

		mask = 0;

		spin_lock_irqsave(&rnp->lock, flags);

		spin_lock_irqsave(&rnp->lock, flags);

		if (rsp->completed != lastcomp) {

		if (rnp->completed != lastcomp) {

			spin_unlock_irqrestore(&rnp->lock, flags);

			spin_unlock_irqrestore(&rnp->lock, flags);

			return 1;

			return 1;

		}

		}
@@ -1159,7 +1157,7 @@ static int rcu_process_dyntick(struct rcu_state *rsp, long lastcomp, 
			if ((rnp->qsmask & bit) != 0 && f(rsp->rda[cpu]))

			if ((rnp->qsmask & bit) != 0 && f(rsp->rda[cpu]))

				mask |= bit;

				mask |= bit;

		}

		}

		if (mask != 0 && rsp->completed == lastcomp) {

		if (mask != 0 && rnp->completed == lastcomp) {





			/* cpu_quiet_msk() releases rnp->lock. */

			/* cpu_quiet_msk() releases rnp->lock. */

			cpu_quiet_msk(mask, rsp, rnp, flags);

			cpu_quiet_msk(mask, rsp, rnp, flags);
@@ -1196,7 +1194,7 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed) 
	lastcomp = rsp->gpnum - 1;

	lastcomp = rsp->gpnum - 1;

	signaled = rsp->signaled;

	signaled = rsp->signaled;

	rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS;

	rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS;

	if (lastcomp == rsp->gpnum) {

	if(!rcu_gp_in_progress(rsp)) {

		rsp->n_force_qs_ngp++;

		rsp->n_force_qs_ngp++;

		spin_unlock(&rnp->lock);

		spin_unlock(&rnp->lock);

		goto unlock_ret;  /* no GP in progress, time updated. */

		goto unlock_ret;  /* no GP in progress, time updated. */
@@ -1224,7 +1222,8 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed) 
		/* Update state, record completion counter. */

		/* Update state, record completion counter. */

		forcenow = 0;

		forcenow = 0;

		spin_lock(&rnp->lock);

		spin_lock(&rnp->lock);

		if (lastcomp == rsp->completed &&

		if (lastcomp + 1 == rsp->gpnum &&

		    lastcomp == rsp->completed &&

		    rsp->signaled == signaled) {

		    rsp->signaled == signaled) {

			rsp->signaled = RCU_FORCE_QS;

			rsp->signaled = RCU_FORCE_QS;

			rsp->completed_fqs = lastcomp;

			rsp->completed_fqs = lastcomp;