rcu: Rename ->onofflock to ->orphan_lock

The ->onofflock field in the rcu_state structure at one time synchronized
CPU-hotplug operations for RCU.  However, its scope has decreased over time
so that it now only protects the lists of orphaned RCU callbacks.  This
commit therefore renames it to ->orphan_lock to reflect its current use.

Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index ac8aed8..8914886 100644 (file)
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -70,7 +70,7 @@ static struct lock_class_key rcu_fqs_class[RCU_NUM_LVLS];
        .fqs_state = RCU_GP_IDLE, \
        .gpnum = -300, \
        .completed = -300, \
-       .onofflock = __RAW_SPIN_LOCK_UNLOCKED(&sname##_state.onofflock), \
+       .orphan_lock = __RAW_SPIN_LOCK_UNLOCKED(&sname##_state.orphan_lock), \
        .orphan_nxttail = &sname##_state.orphan_nxtlist, \
        .orphan_donetail = &sname##_state.orphan_donelist, \
        .barrier_mutex = __MUTEX_INITIALIZER(sname##_state.barrier_mutex), \
@@ -1573,7 +1573,7 @@ rcu_check_quiescent_state(struct rcu_state *rsp, struct rcu_data *rdp)
 /*
  * Send the specified CPU's RCU callbacks to the orphanage.  The
  * specified CPU must be offline, and the caller must hold the
- * ->onofflock.
+ * ->orphan_lock.
  */
 static void
 rcu_send_cbs_to_orphanage(int cpu, struct rcu_state *rsp,
@@ -1623,7 +1623,7 @@ 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 ->onofflock.
+ * orphanage.  The caller must hold the ->orphan_lock.
  */
 static void rcu_adopt_orphan_cbs(struct rcu_state *rsp)
 {
@@ -1702,7 +1702,7 @@ static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp)
 
        /* Exclude any attempts to start a new grace period. */
        mutex_lock(&rsp->onoff_mutex);
-       raw_spin_lock_irqsave(&rsp->onofflock, flags);
+       raw_spin_lock_irqsave(&rsp->orphan_lock, flags);
 
        /* Orphan the dead CPU's callbacks, and adopt them if appropriate. */
        rcu_send_cbs_to_orphanage(cpu, rsp, rnp, rdp);
@@ -1729,10 +1729,10 @@ static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp)
        /*
         * We still hold the leaf rcu_node structure lock here, and
         * irqs are still disabled.  The reason for this subterfuge is
-        * because invoking rcu_report_unblock_qs_rnp() with ->onofflock
+        * because invoking rcu_report_unblock_qs_rnp() with ->orphan_lock
         * held leads to deadlock.
         */
-       raw_spin_unlock(&rsp->onofflock); /* irqs remain disabled. */
+       raw_spin_unlock(&rsp->orphan_lock); /* irqs remain disabled. */
        rnp = rdp->mynode;
        if (need_report & RCU_OFL_TASKS_NORM_GP)
                rcu_report_unblock_qs_rnp(rnp, flags);

diff --git a/kernel/rcutree.h b/kernel/rcutree.h
index a240f03..a7c945d 100644 (file)
--- a/kernel/rcutree.h
+++ b/kernel/rcutree.h
@@ -383,9 +383,8 @@ struct rcu_state {
 
        /* End of fields guarded by root rcu_node's lock. */
 
-       raw_spinlock_t onofflock ____cacheline_internodealigned_in_smp;
-                                               /* exclude on/offline and */
-                                               /*  starting new GP. */
+       raw_spinlock_t orphan_lock ____cacheline_internodealigned_in_smp;
+                                               /* Protect following fields. */
        struct rcu_head *orphan_nxtlist;        /* Orphaned callbacks that */
                                                /*  need a grace period. */
        struct rcu_head **orphan_nxttail;       /* Tail of above. */
@@ -394,7 +393,7 @@ struct rcu_state {
        struct rcu_head **orphan_donetail;      /* Tail of above. */
        long qlen_lazy;                         /* Number of lazy callbacks. */
        long qlen;                              /* Total number of callbacks. */
-       /* End of fields guarded by onofflock. */
+       /* End of fields guarded by orphan_lock. */
 
        struct mutex onoff_mutex;               /* Coordinate hotplug & GPs. */
 

diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index f921154..2b281cf 100644 (file)
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -757,7 +757,8 @@ static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp,
  * grace period for the specified rcu_node structure.  If there are no such
  * tasks, report it up the rcu_node hierarchy.
  *
- * Caller must hold sync_rcu_preempt_exp_mutex and rsp->onofflock.
+ * Caller must hold sync_rcu_preempt_exp_mutex and must exclude
+ * CPU hotplug operations.
  */
 static void
 sync_rcu_preempt_exp_init(struct rcu_state *rsp, struct rcu_node *rnp)