Commit ec9f5835 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

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: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent 67a0edbf

kernel/rcu/tree.c

+32 −33
Original line number Diff line number Diff line
@@ -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);

}



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