From dd46a7882c2c2006201e053ebf5e9ad761860cc0 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Tue, 10 Jul 2018 18:37:30 -0700 Subject: [PATCH] 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 --- 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 e140aaa78527..ce16b8da2c6f 100644 --- 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 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 -- 2.45.2