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Subject[PATCH tip/core/rcu 02/11] rcu: adjust force_quiescent_state() locking, step 2
Date
From: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

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>
---
kernel/rcutree.c | 13 +++----------
1 files changed, 3 insertions(+), 10 deletions(-)

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index eae331d..d42ad30 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -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);
}
--
1.5.2.5


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