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: Paul 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: Ingo Molnar <mingo@elte.hu>
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@ -1219,7 +1219,6 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed)
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case RCU_GP_IDLE:
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case RCU_GP_INIT:
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spin_unlock(&rnp->lock);
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break; /* grace period idle or initializing, ignore. */
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case RCU_SAVE_DYNTICK:
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@ -1246,10 +1245,8 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed)
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rsp->completed_fqs = lastcomp;
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forcenow = signaled == RCU_SAVE_COMPLETED;
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}
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if (!forcenow) {
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spin_unlock(&rnp->lock);
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if (!forcenow)
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break;
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}
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/* fall into next case. */
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case RCU_FORCE_QS:
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@ -1262,14 +1259,10 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed)
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/* Leave state in case more forcing is required. */
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break;
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default:
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spin_unlock(&rnp->lock);
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WARN_ON_ONCE(1);
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spin_lock(&rnp->lock);
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break;
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}
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spin_unlock(&rnp->lock);
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unlock_fqs_ret:
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spin_unlock_irqrestore(&rsp->fqslock, flags);
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}
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