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rcu: Eliminate rcu_state ->orphan_lock

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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: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Paul E. McKenney 2017-06-26 17:59:02 -07:00
parent 9fa46fb8c9
commit 537b85c870
2 changed files with 3 additions and 15 deletions
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15
kernel/rcu/tree.c
View File

@ -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",

3
kernel/rcu/tree.h
View File

@ -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. */