rcu: Eliminate RCU-barrier use of rsp

Now that there is only one rcu_state structure, there is less point
in maintaining a pointer to it.  This commit therefore replaces rsp
with &rcu_state in rcu_barrier_callback(), rcu_barrier_func(), and
_rcu_barrier().

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

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index f329282..ce5fb17 100644 (file)
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3129,32 +3129,31 @@ static void _rcu_barrier_trace(const char *s, int cpu, unsigned long done)
  */
 static void rcu_barrier_callback(struct rcu_head *rhp)
 {
-       struct rcu_state *rsp = &rcu_state;
-
-       if (atomic_dec_and_test(&rsp->barrier_cpu_count)) {
-               _rcu_barrier_trace(TPS("LastCB"), -1, rsp->barrier_sequence);
-               complete(&rsp->barrier_completion);
+       if (atomic_dec_and_test(&rcu_state.barrier_cpu_count)) {
+               _rcu_barrier_trace(TPS("LastCB"), -1,
+                                  rcu_state.barrier_sequence);
+               complete(&rcu_state.barrier_completion);
        } else {
-               _rcu_barrier_trace(TPS("CB"), -1, rsp->barrier_sequence);
+               _rcu_barrier_trace(TPS("CB"), -1, rcu_state.barrier_sequence);
        }
 }
 
 /*
  * Called with preemption disabled, and from cross-cpu IRQ context.
  */
-static void rcu_barrier_func(void *type)
+static void rcu_barrier_func(void *unused)
 {
-       struct rcu_state *rsp = type;
        struct rcu_data *rdp = raw_cpu_ptr(&rcu_data);
 
-       _rcu_barrier_trace(TPS("IRQ"), -1, rsp->barrier_sequence);
+       _rcu_barrier_trace(TPS("IRQ"), -1, rcu_state.barrier_sequence);
        rdp->barrier_head.func = rcu_barrier_callback;
        debug_rcu_head_queue(&rdp->barrier_head);
        if (rcu_segcblist_entrain(&rdp->cblist, &rdp->barrier_head, 0)) {
-               atomic_inc(&rsp->barrier_cpu_count);
+               atomic_inc(&rcu_state.barrier_cpu_count);
        } else {
                debug_rcu_head_unqueue(&rdp->barrier_head);
-               _rcu_barrier_trace(TPS("IRQNQ"), -1, rsp->barrier_sequence);
+               _rcu_barrier_trace(TPS("IRQNQ"), -1,
+                                  rcu_state.barrier_sequence);
        }
 }
 
@@ -3166,25 +3165,25 @@ static void _rcu_barrier(void)
 {
        int cpu;
        struct rcu_data *rdp;
-       struct rcu_state *rsp = &rcu_state;
-       unsigned long s = rcu_seq_snap(&rsp->barrier_sequence);
+       unsigned long s = rcu_seq_snap(&rcu_state.barrier_sequence);
 
        _rcu_barrier_trace(TPS("Begin"), -1, s);
 
        /* Take mutex to serialize concurrent rcu_barrier() requests. */
-       mutex_lock(&rsp->barrier_mutex);
+       mutex_lock(&rcu_state.barrier_mutex);
 
        /* Did someone else do our work for us? */
-       if (rcu_seq_done(&rsp->barrier_sequence, s)) {
-               _rcu_barrier_trace(TPS("EarlyExit"), -1, rsp->barrier_sequence);
+       if (rcu_seq_done(&rcu_state.barrier_sequence, s)) {
+               _rcu_barrier_trace(TPS("EarlyExit"), -1,
+                                  rcu_state.barrier_sequence);
                smp_mb(); /* caller's subsequent code after above check. */
-               mutex_unlock(&rsp->barrier_mutex);
+               mutex_unlock(&rcu_state.barrier_mutex);
                return;
        }
 
        /* Mark the start of the barrier operation. */
-       rcu_seq_start(&rsp->barrier_sequence);
-       _rcu_barrier_trace(TPS("Inc1"), -1, rsp->barrier_sequence);
+       rcu_seq_start(&rcu_state.barrier_sequence);
+       _rcu_barrier_trace(TPS("Inc1"), -1, rcu_state.barrier_sequence);
 
        /*
         * Initialize the count to one rather than to zero in order to
@@ -3192,8 +3191,8 @@ static void _rcu_barrier(void)
         * (or preemption of this task).  Exclude CPU-hotplug operations
         * to ensure that no offline CPU has callbacks queued.
         */
-       init_completion(&rsp->barrier_completion);
-       atomic_set(&rsp->barrier_cpu_count, 1);
+       init_completion(&rcu_state.barrier_completion);
+       atomic_set(&rcu_state.barrier_cpu_count, 1);
        get_online_cpus();
 
        /*
@@ -3208,22 +3207,22 @@ static void _rcu_barrier(void)
                if (rcu_is_nocb_cpu(cpu)) {
                        if (!rcu_nocb_cpu_needs_barrier(cpu)) {
                                _rcu_barrier_trace(TPS("OfflineNoCB"), cpu,
-                                                  rsp->barrier_sequence);
+                                                  rcu_state.barrier_sequence);
                        } else {
                                _rcu_barrier_trace(TPS("OnlineNoCB"), cpu,
-                                                  rsp->barrier_sequence);
+                                                  rcu_state.barrier_sequence);
                                smp_mb__before_atomic();
-                               atomic_inc(&rsp->barrier_cpu_count);
+                               atomic_inc(&rcu_state.barrier_cpu_count);
                                __call_rcu(&rdp->barrier_head,
                                           rcu_barrier_callback, cpu, 0);
                        }
                } else if (rcu_segcblist_n_cbs(&rdp->cblist)) {
                        _rcu_barrier_trace(TPS("OnlineQ"), cpu,
-                                          rsp->barrier_sequence);
-                       smp_call_function_single(cpu, rcu_barrier_func, rsp, 1);
+                                          rcu_state.barrier_sequence);
+                       smp_call_function_single(cpu, rcu_barrier_func, NULL, 1);
                } else {
                        _rcu_barrier_trace(TPS("OnlineNQ"), cpu,
-                                          rsp->barrier_sequence);
+                                          rcu_state.barrier_sequence);
                }
        }
        put_online_cpus();
@@ -3232,18 +3231,18 @@ static void _rcu_barrier(void)
         * Now that we have an rcu_barrier_callback() callback on each
         * CPU, and thus each counted, remove the initial count.
         */
-       if (atomic_dec_and_test(&rsp->barrier_cpu_count))
-               complete(&rsp->barrier_completion);
+       if (atomic_dec_and_test(&rcu_state.barrier_cpu_count))
+               complete(&rcu_state.barrier_completion);
 
        /* Wait for all rcu_barrier_callback() callbacks to be invoked. */
-       wait_for_completion(&rsp->barrier_completion);
+       wait_for_completion(&rcu_state.barrier_completion);
 
        /* Mark the end of the barrier operation. */
-       _rcu_barrier_trace(TPS("Inc2"), -1, rsp->barrier_sequence);
-       rcu_seq_end(&rsp->barrier_sequence);
+       _rcu_barrier_trace(TPS("Inc2"), -1, rcu_state.barrier_sequence);
+       rcu_seq_end(&rcu_state.barrier_sequence);
 
        /* Other rcu_barrier() invocations can now safely proceed. */
-       mutex_unlock(&rsp->barrier_mutex);
+       mutex_unlock(&rcu_state.barrier_mutex);
 }
 
 /**