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Commit 559569ac authored by Paul E. McKenney's avatar Paul E. McKenney Committed by Ingo Molnar
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rcu: Adjust force_quiescent_state() locking, step 2 



This patch releases rnp->lock after the end of
force_quiescent_state()'s switch statement.  This is a second
step towards prohibiting starting grace periods while
force_quiescent_state() is executing, which will reduce the
number and complexity of races that force_quiescent_state() is
involved in.

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: <12626465501994-git-send-email->
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent f96e9232

kernel/rcutree.c

+3 −10
Original line number Original line Diff line number Diff line
@@ -1219,7 +1219,6 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed) 
	case RCU_GP_IDLE:

	case RCU_GP_IDLE:

	case RCU_GP_INIT:

	case RCU_GP_INIT:





		spin_unlock(&rnp->lock);

		break; /* grace period idle or initializing, ignore. */

		break; /* grace period idle or initializing, ignore. */





	case RCU_SAVE_DYNTICK:

	case RCU_SAVE_DYNTICK:
@@ -1246,10 +1245,8 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed) 
			rsp->completed_fqs = lastcomp;

			rsp->completed_fqs = lastcomp;

			forcenow = signaled == RCU_SAVE_COMPLETED;

			forcenow = signaled == RCU_SAVE_COMPLETED;

		}

		}

		if (!forcenow) {

		if (!forcenow)

			spin_unlock(&rnp->lock);

			break;

			break;

		}

		/* fall into next case. */

		/* fall into next case. */





	case RCU_FORCE_QS:

	case RCU_FORCE_QS:
@@ -1262,14 +1259,10 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed) 




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

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





		break;

		spin_lock(&rnp->lock);



	default:



		spin_unlock(&rnp->lock);

		WARN_ON_ONCE(1);

		break;

		break;

	}

	}

	spin_unlock(&rnp->lock);

unlock_fqs_ret:

unlock_fqs_ret:

	spin_unlock_irqrestore(&rsp->fqslock, flags);

	spin_unlock_irqrestore(&rsp->fqslock, flags);

}

}