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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: 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>
This commit is contained in:
Paul E. McKenney 2010-01-04 15:09:01 -08:00 committed by Ingo Molnar
parent f96e9232e0
commit 559569acf9
1 changed files with 3 additions and 10 deletions
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13
kernel/rcutree.c
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@ -1219,7 +1219,6 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed)
case RCU_GP_IDLE:
case RCU_GP_INIT:
spin_unlock(&rnp->lock);
break; /* grace period idle or initializing, ignore. */
case RCU_SAVE_DYNTICK:
@ -1246,10 +1245,8 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed)
rsp->completed_fqs = lastcomp;
forcenow = signaled == RCU_SAVE_COMPLETED;
}
if (!forcenow) {
spin_unlock(&rnp->lock);
if (!forcenow)
break;
}
/* fall into next case. */
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. */
break;
default:
spin_unlock(&rnp->lock);
WARN_ON_ONCE(1);
spin_lock(&rnp->lock);
break;
}
spin_unlock(&rnp->lock);
unlock_fqs_ret:
spin_unlock_irqrestore(&rsp->fqslock, flags);
}