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Commit 0f10dc82 authored by Paul E. McKenney's avatar Paul E. McKenney Committed by Ingo Molnar
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rcu: Eliminate rcu_process_dyntick() return value 



Because a new grace period cannot start while we are executing
within the force_quiescent_state() function's switch statement,
if any test within that switch statement or within any function
called from that switch statement shows that the current grace
period has ended, we can safely re-do that test any time before
we leave the switch statement.  This means that we no longer
need a return value from rcu_process_dyntick(), as we can simply
invoke rcu_gp_in_progress() to check whether the old grace
period has finished -- there is no longer any need to worry
about whether or not a new grace period has been started.

Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: mathieu.desnoyers@polymtl.ca
Cc: josh@joshtriplett.org
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: Valdis.Kletnieks@vt.edu
Cc: dhowells@redhat.com
LKML-Reference: <12626465501857-git-send-email->
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent eb1ba45f

kernel/rcutree.c

+6 −11
Original line number Diff line number Diff line
@@ -1144,10 +1144,8 @@ void rcu_check_callbacks(int cpu, int user) 
/*

 * Scan the leaf rcu_node structures, processing dyntick state for any that

 * have not yet encountered a quiescent state, using the function specified.

 * Returns 1 if the current grace period ends while scanning (possibly

 * because we made it end).

 */

static int rcu_process_dyntick(struct rcu_state *rsp,

static void rcu_process_dyntick(struct rcu_state *rsp,

				int (*f)(struct rcu_data *))

{

	unsigned long bit;
@@ -1161,7 +1159,7 @@ static int rcu_process_dyntick(struct rcu_state *rsp, 
		spin_lock_irqsave(&rnp->lock, flags);

		if (rnp->completed != rsp->gpnum - 1) {

			spin_unlock_irqrestore(&rnp->lock, flags);

			return 1;

			return;

		}

		if (rnp->qsmask == 0) {

			spin_unlock_irqrestore(&rnp->lock, flags);
@@ -1181,7 +1179,6 @@ static int rcu_process_dyntick(struct rcu_state *rsp, 
		}

		spin_unlock_irqrestore(&rnp->lock, flags);

	}

	return 0;

}



/*
@@ -1193,7 +1190,6 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed) 
	unsigned long flags;

	struct rcu_node *rnp = rcu_get_root(rsp);

	u8 forcenow;

	u8 gpdone;



	if (!rcu_gp_in_progress(rsp))

		return;  /* No grace period in progress, nothing to force. */
@@ -1226,10 +1222,9 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed) 
			break; /* So gcc recognizes the dead code. */



		/* Record dyntick-idle state. */

		gpdone = rcu_process_dyntick(rsp,

					     dyntick_save_progress_counter);

		rcu_process_dyntick(rsp, dyntick_save_progress_counter);

		spin_lock(&rnp->lock);  /* irqs already disabled */

		if (gpdone)

		if (!rcu_gp_in_progress(rsp))

			break;

		/* fall into next case. */
@@ -1249,7 +1244,7 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed) 


		/* Check dyntick-idle state, send IPI to laggarts. */

		spin_unlock(&rnp->lock);  /* irqs remain disabled */

		gpdone = rcu_process_dyntick(rsp, rcu_implicit_dynticks_qs);

		rcu_process_dyntick(rsp, rcu_implicit_dynticks_qs);



		/* Leave state in case more forcing is required. */