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Commit 537b85c8 authored by Paul E. McKenney's avatar Paul E. McKenney
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rcu: Eliminate rcu_state ->orphan_lock 



The ->orphan_lock is acquired and released only within the
rcu_migrate_callbacks() function, which now acquires the root rcu_node
structure's ->lock.  This commit therefore eliminates the ->orphan_lock
in favor of the root rcu_node structure's ->lock.

Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent 9fa46fb8

kernel/rcu/tree.c

+3 −12
Original line number Diff line number Diff line
@@ -97,7 +97,6 @@ struct rcu_state sname##_state = { \ 
	.gp_state = RCU_GP_IDLE, \

	.gpnum = 0UL - 300UL, \

	.completed = 0UL - 300UL, \

	.orphan_lock = __RAW_SPIN_LOCK_UNLOCKED(&sname##_state.orphan_lock), \

	.orphan_pend = RCU_CBLIST_INITIALIZER(sname##_state.orphan_pend), \

	.orphan_done = RCU_CBLIST_INITIALIZER(sname##_state.orphan_done), \

	.barrier_mutex = __MUTEX_INITIALIZER(sname##_state.barrier_mutex), \
@@ -3853,15 +3852,12 @@ void rcu_report_dead(unsigned int cpu) 


/*

 * Send the specified CPU's RCU callbacks to the orphanage.  The

 * specified CPU must be offline, and the caller must hold the

 * ->orphan_lock.

 * specified CPU must be offline.

 */

static void

rcu_send_cbs_to_orphanage(int cpu, struct rcu_state *rsp,

			  struct rcu_node *rnp, struct rcu_data *rdp)

{

	lockdep_assert_held(&rsp->orphan_lock);



	/*

	 * Orphan the callbacks.  First adjust the counts.  This is safe

	 * because _rcu_barrier() excludes CPU-hotplug operations, so it
@@ -3891,14 +3887,12 @@ rcu_send_cbs_to_orphanage(int cpu, struct rcu_state *rsp, 


/*

 * Adopt the RCU callbacks from the specified rcu_state structure's

 * orphanage.  The caller must hold the ->orphan_lock.

 * orphanage.

 */

static void rcu_adopt_orphan_cbs(struct rcu_state *rsp, unsigned long flags)

{

	struct rcu_data *rdp = raw_cpu_ptr(rsp->rda);



	lockdep_assert_held(&rsp->orphan_lock);



	/* Do the accounting first. */

	if (rsp->orphan_done.len_lazy != rsp->orphan_done.len)

		rcu_idle_count_callbacks_posted();
@@ -3939,12 +3933,9 @@ static void rcu_migrate_callbacks(int cpu, struct rcu_state *rsp) 
	}

	raw_spin_lock_rcu_node(rnp_root); /* irqs already disabled. */

	rcu_advance_cbs(rsp, rnp_root, rdp); /* Leverage recent GPs. */

	raw_spin_unlock_rcu_node(rnp_root);



	raw_spin_lock(&rsp->orphan_lock);

	rcu_send_cbs_to_orphanage(cpu, rsp, rnp, rdp);

	rcu_adopt_orphan_cbs(rsp, flags);

	raw_spin_unlock_irqrestore(&rsp->orphan_lock, flags);

	raw_spin_unlock_irqrestore_rcu_node(rnp_root, flags);

	WARN_ONCE(rcu_segcblist_n_cbs(&rdp->cblist) != 0 ||

		  !rcu_segcblist_empty(&rdp->cblist),

		  "rcu_cleanup_dead_cpu: Callbacks on offline CPU %d: qlen=%lu, 1stCB=%p\n",

kernel/rcu/tree.h

+0 −3
Original line number Diff line number Diff line
@@ -348,14 +348,11 @@ struct rcu_state { 


	/* End of fields guarded by root rcu_node's lock. */



	raw_spinlock_t orphan_lock ____cacheline_internodealigned_in_smp;

						/* Protect following fields. */

	struct rcu_cblist orphan_pend;		/* Orphaned callbacks that */

						/*  need a grace period. */

	struct rcu_cblist orphan_done;		/* Orphaned callbacks that */

						/*  are ready to invoke. */

						/* (Contains counts.) */

	/* End of fields guarded by orphan_lock. */



	struct mutex barrier_mutex;		/* Guards barrier fields. */

	atomic_t barrier_cpu_count;		/* # CPUs waiting on. */