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Message-Id: <20180829225405.7275-24-paulmck@linux.vnet.ibm.com>
Date: Wed, 29 Aug 2018 15:54:05 -0700
From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To: linux-kernel@...r.kernel.org
Cc: mingo@...nel.org, jiangshanlai@...il.com, dipankar@...ibm.com,
akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
josh@...htriplett.org, tglx@...utronix.de, peterz@...radead.org,
rostedt@...dmis.org, dhowells@...hat.com, edumazet@...gle.com,
fweisbec@...il.com, oleg@...hat.com, joel@...lfernandes.org,
"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: [PATCH tip/core/rcu 24/24] 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@...ux.vnet.ibm.com>
---
include/trace/events/rcu.h | 20 ++++++-------
kernel/rcu/tree.c | 58 +++++++++++++++++---------------------
kernel/rcu/tree.h | 4 +--
kernel/rcu/tree_plugin.h | 2 +-
4 files changed, 39 insertions(+), 45 deletions(-)
diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h
index a8d07feff6a0..175e0bce22bd 100644
--- 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 5f2a12a65b42..31e94f672d01 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -2746,7 +2746,7 @@ 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
@@ -2980,27 +2980,27 @@ 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);
}
}
@@ -3011,33 +3011,40 @@ 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);
@@ -3046,7 +3053,7 @@ 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
@@ -3069,10 +3076,10 @@ 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);
@@ -3080,11 +3087,11 @@ 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);
}
}
@@ -3101,25 +3108,12 @@ 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 46452d3d0fad..8cf93ac277ec 100644
--- 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 7add1c297500..beaaca7a11f4 100644
--- 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
--
2.17.1
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