rcu: Inline _rcu_barrier() into its sole remaining caller

Because rcu_barrier() is a one-line wrapper function for _rcu_barrier()
and because nothing else calls _rcu_barrier(), this commit inlines
_rcu_barrier() into rcu_barrier().

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

diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h
index a8d07fe..175e0bc 100644 (file)
--- a/include/trace/events/rcu.h
+++ b/include/trace/events/rcu.h
@@ -705,20 +705,20 @@ TRACE_EVENT(rcu_torture_read,
 );
 
 /*
- * Tracepoint for _rcu_barrier() execution.  The string "s" describes
- * the _rcu_barrier phase:
- *     "Begin": _rcu_barrier() started.
- *     "EarlyExit": _rcu_barrier() piggybacked, thus early exit.
- *     "Inc1": _rcu_barrier() piggyback check counter incremented.
- *     "OfflineNoCB": _rcu_barrier() found callback on never-online CPU
- *     "OnlineNoCB": _rcu_barrier() found online no-CBs CPU.
- *     "OnlineQ": _rcu_barrier() found online CPU with callbacks.
- *     "OnlineNQ": _rcu_barrier() found online CPU, no callbacks.
+ * Tracepoint for rcu_barrier() execution.  The string "s" describes
+ * the rcu_barrier phase:
+ *     "Begin": rcu_barrier() started.
+ *     "EarlyExit": rcu_barrier() piggybacked, thus early exit.
+ *     "Inc1": rcu_barrier() piggyback check counter incremented.
+ *     "OfflineNoCB": rcu_barrier() found callback on never-online CPU
+ *     "OnlineNoCB": rcu_barrier() found online no-CBs CPU.
+ *     "OnlineQ": rcu_barrier() found online CPU with callbacks.
+ *     "OnlineNQ": rcu_barrier() found online CPU, no callbacks.
  *     "IRQ": An rcu_barrier_callback() callback posted on remote CPU.
  *     "IRQNQ": An rcu_barrier_callback() callback found no callbacks.
  *     "CB": An rcu_barrier_callback() invoked a callback, not the last.
  *     "LastCB": An rcu_barrier_callback() invoked the last callback.
- *     "Inc2": _rcu_barrier() piggyback check counter incremented.
+ *     "Inc2": rcu_barrier() piggyback check counter incremented.
  * The "cpu" argument is the CPU or -1 if meaningless, the "cnt" argument
  * is the count of remaining callbacks, and "done" is the piggybacking count.
  */

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index e140aaa..ce16b8d 100644 (file)
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -2747,7 +2747,7 @@ static void rcu_leak_callback(struct rcu_head *rhp)
 /*
  * Helper function for call_rcu() and friends.  The cpu argument will
  * normally be -1, indicating "currently running CPU".  It may specify
- * a CPU only if that CPU is a no-CBs CPU.  Currently, only _rcu_barrier()
+ * a CPU only if that CPU is a no-CBs CPU.  Currently, only rcu_barrier()
  * is expected to specify a CPU.
  */
 static void
@@ -2981,27 +2981,27 @@ static bool rcu_cpu_has_callbacks(bool *all_lazy)
 }
 
 /*
- * Helper function for _rcu_barrier() tracing.  If tracing is disabled,
+ * Helper function for rcu_barrier() tracing.  If tracing is disabled,
  * the compiler is expected to optimize this away.
  */
-static void _rcu_barrier_trace(const char *s, int cpu, unsigned long done)
+static void rcu_barrier_trace(const char *s, int cpu, unsigned long done)
 {
        trace_rcu_barrier(rcu_state.name, s, cpu,
                          atomic_read(&rcu_state.barrier_cpu_count), done);
 }
 
 /*
- * RCU callback function for _rcu_barrier().  If we are last, wake
- * up the task executing _rcu_barrier().
+ * RCU callback function for rcu_barrier().  If we are last, wake
+ * up the task executing rcu_barrier().
  */
 static void rcu_barrier_callback(struct rcu_head *rhp)
 {
        if (atomic_dec_and_test(&rcu_state.barrier_cpu_count)) {
-               _rcu_barrier_trace(TPS("LastCB"), -1,
+               rcu_barrier_trace(TPS("LastCB"), -1,
                                   rcu_state.barrier_sequence);
                complete(&rcu_state.barrier_completion);
        } else {
-               _rcu_barrier_trace(TPS("CB"), -1, rcu_state.barrier_sequence);
+               rcu_barrier_trace(TPS("CB"), -1, rcu_state.barrier_sequence);
        }
 }
 
@@ -3012,33 +3012,40 @@ static void rcu_barrier_func(void *unused)
 {
        struct rcu_data *rdp = raw_cpu_ptr(&rcu_data);
 
-       _rcu_barrier_trace(TPS("IRQ"), -1, rcu_state.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(&rcu_state.barrier_cpu_count);
        } else {
                debug_rcu_head_unqueue(&rdp->barrier_head);
-               _rcu_barrier_trace(TPS("IRQNQ"), -1,
+               rcu_barrier_trace(TPS("IRQNQ"), -1,
                                   rcu_state.barrier_sequence);
        }
 }
 
-/* Orchestrate an RCU barrier, waiting for all RCU callbacks to complete.  */
-static void _rcu_barrier(void)
+/**
+ * rcu_barrier - Wait until all in-flight call_rcu() callbacks complete.
+ *
+ * Note that this primitive does not necessarily wait for an RCU grace period
+ * to complete.  For example, if there are no RCU callbacks queued anywhere
+ * in the system, then rcu_barrier() is within its rights to return
+ * immediately, without waiting for anything, much less an RCU grace period.
+ */
+void rcu_barrier(void)
 {
        int cpu;
        struct rcu_data *rdp;
        unsigned long s = rcu_seq_snap(&rcu_state.barrier_sequence);
 
-       _rcu_barrier_trace(TPS("Begin"), -1, s);
+       rcu_barrier_trace(TPS("Begin"), -1, s);
 
        /* Take mutex to serialize concurrent rcu_barrier() requests. */
        mutex_lock(&rcu_state.barrier_mutex);
 
        /* Did someone else do our work for us? */
        if (rcu_seq_done(&rcu_state.barrier_sequence, s)) {
-               _rcu_barrier_trace(TPS("EarlyExit"), -1,
+               rcu_barrier_trace(TPS("EarlyExit"), -1,
                                   rcu_state.barrier_sequence);
                smp_mb(); /* caller's subsequent code after above check. */
                mutex_unlock(&rcu_state.barrier_mutex);
@@ -3047,7 +3054,7 @@ static void _rcu_barrier(void)
 
        /* Mark the start of the barrier operation. */
        rcu_seq_start(&rcu_state.barrier_sequence);
-       _rcu_barrier_trace(TPS("Inc1"), -1, 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
@@ -3070,10 +3077,10 @@ static void _rcu_barrier(void)
                rdp = per_cpu_ptr(&rcu_data, cpu);
                if (rcu_is_nocb_cpu(cpu)) {
                        if (!rcu_nocb_cpu_needs_barrier(cpu)) {
-                               _rcu_barrier_trace(TPS("OfflineNoCB"), cpu,
+                               rcu_barrier_trace(TPS("OfflineNoCB"), cpu,
                                                   rcu_state.barrier_sequence);
                        } else {
-                               _rcu_barrier_trace(TPS("OnlineNoCB"), cpu,
+                               rcu_barrier_trace(TPS("OnlineNoCB"), cpu,
                                                   rcu_state.barrier_sequence);
                                smp_mb__before_atomic();
                                atomic_inc(&rcu_state.barrier_cpu_count);
@@ -3081,11 +3088,11 @@ static void _rcu_barrier(void)
                                           rcu_barrier_callback, cpu, 0);
                        }
                } else if (rcu_segcblist_n_cbs(&rdp->cblist)) {
-                       _rcu_barrier_trace(TPS("OnlineQ"), cpu,
+                       rcu_barrier_trace(TPS("OnlineQ"), cpu,
                                           rcu_state.barrier_sequence);
                        smp_call_function_single(cpu, rcu_barrier_func, NULL, 1);
                } else {
-                       _rcu_barrier_trace(TPS("OnlineNQ"), cpu,
+                       rcu_barrier_trace(TPS("OnlineNQ"), cpu,
                                           rcu_state.barrier_sequence);
                }
        }
@@ -3102,25 +3109,12 @@ static void _rcu_barrier(void)
        wait_for_completion(&rcu_state.barrier_completion);
 
        /* Mark the end of the barrier operation. */
-       _rcu_barrier_trace(TPS("Inc2"), -1, rcu_state.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(&rcu_state.barrier_mutex);
 }
-
-/**
- * rcu_barrier - Wait until all in-flight call_rcu() callbacks complete.
- *
- * Note that this primitive does not necessarily wait for an RCU grace period
- * to complete.  For example, if there are no RCU callbacks queued anywhere
- * in the system, then rcu_barrier() is within its rights to return
- * immediately, without waiting for anything, much less an RCU grace period.
- */
-void rcu_barrier(void)
-{
-       _rcu_barrier();
-}
 EXPORT_SYMBOL_GPL(rcu_barrier);
 
 /*

diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
index 46452d3..8cf93ac 100644 (file)
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -222,7 +222,7 @@ struct rcu_data {
                                        /* Grace period that needs help */
                                        /*  from cond_resched(). */
 
-       /* 5) _rcu_barrier(), OOM callbacks, and expediting. */
+       /* 5) rcu_barrier(), OOM callbacks, and expediting. */
        struct rcu_head barrier_head;
        int exp_dynticks_snap;          /* Double-check need for IPI. */
 
@@ -328,7 +328,7 @@ struct rcu_state {
        atomic_t barrier_cpu_count;             /* # CPUs waiting on. */
        struct completion barrier_completion;   /* Wake at barrier end. */
        unsigned long barrier_sequence;         /* ++ at start and end of */
-                                               /*  _rcu_barrier(). */
+                                               /*  rcu_barrier(). */
        /* End of fields guarded by barrier_mutex. */
 
        struct mutex exp_mutex;                 /* Serialize expedited GP. */

diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 7add1c2..beaaca7 100644 (file)
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -1993,7 +1993,7 @@ static bool rcu_nocb_cpu_needs_barrier(int cpu)
         * There needs to be a barrier before this function is called,
         * but associated with a prior determination that no more
         * callbacks would be posted.  In the worst case, the first
-        * barrier in _rcu_barrier() suffices (but the caller cannot
+        * barrier in rcu_barrier() suffices (but the caller cannot
         * necessarily rely on this, not a substitute for the caller
         * getting the concurrency design right!).  There must also be
         * a barrier between the following load an posting of a callback