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Subject[tip:core/rcu] rcu: Further cleanups of use of lastcomp
Commit-ID:  560d4bc0df9a5e63b980432282d8c2bd3559ec74
Gitweb: http://git.kernel.org/tip/560d4bc0df9a5e63b980432282d8c2bd3559ec74
Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
AuthorDate: Fri, 13 Nov 2009 19:51:38 -0800
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Sat, 14 Nov 2009 10:31:42 +0100

rcu: Further cleanups of use of lastcomp

Now that a copy of the rsp->completed flag is available in all
rcu_node structures, make full use of it. It is still
legitimate to access rsp->completed while holding the root
rcu_node structure's lock, however.

Also, tighten up force_quiescent_state()'s checks for end of
current grace period.

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: <1258170699933-git-send-email->
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
kernel/rcutree.c | 13 ++++++-------
1 files changed, 6 insertions(+), 7 deletions(-)
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 3df0438..24bbf2c 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -817,7 +817,7 @@ cpu_quiet(int cpu, struct rcu_state *rsp, struct rcu_data *rdp, long lastcomp)

rnp = rdp->mynode;
spin_lock_irqsave(&rnp->lock, flags);
- if (lastcomp != ACCESS_ONCE(rsp->completed)) {
+ if (lastcomp != rnp->completed) {

/*
* Someone beat us to it for this grace period, so leave.
@@ -935,7 +935,6 @@ static void rcu_adopt_orphan_cbs(struct rcu_state *rsp)
static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp)
{
unsigned long flags;
- long lastcomp;
unsigned long mask;
struct rcu_data *rdp = rsp->rda[cpu];
struct rcu_node *rnp;
@@ -971,7 +970,6 @@ static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp)
spin_unlock(&rnp->lock); /* irqs remain disabled. */
rnp = rnp->parent;
} while (rnp != NULL);
- lastcomp = rsp->completed;

spin_unlock_irqrestore(&rsp->onofflock, flags);

@@ -1145,7 +1143,7 @@ static int rcu_process_dyntick(struct rcu_state *rsp, long lastcomp,
rcu_for_each_leaf_node(rsp, rnp) {
mask = 0;
spin_lock_irqsave(&rnp->lock, flags);
- if (rsp->completed != lastcomp) {
+ if (rnp->completed != lastcomp) {
spin_unlock_irqrestore(&rnp->lock, flags);
return 1;
}
@@ -1159,7 +1157,7 @@ static int rcu_process_dyntick(struct rcu_state *rsp, long lastcomp,
if ((rnp->qsmask & bit) != 0 && f(rsp->rda[cpu]))
mask |= bit;
}
- if (mask != 0 && rsp->completed == lastcomp) {
+ if (mask != 0 && rnp->completed == lastcomp) {

/* cpu_quiet_msk() releases rnp->lock. */
cpu_quiet_msk(mask, rsp, rnp, flags);
@@ -1196,7 +1194,7 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed)
lastcomp = rsp->gpnum - 1;
signaled = rsp->signaled;
rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS;
- if (lastcomp == rsp->gpnum) {
+ if(!rcu_gp_in_progress(rsp)) {
rsp->n_force_qs_ngp++;
spin_unlock(&rnp->lock);
goto unlock_ret; /* no GP in progress, time updated. */
@@ -1224,7 +1222,8 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed)
/* Update state, record completion counter. */
forcenow = 0;
spin_lock(&rnp->lock);
- if (lastcomp == rsp->completed &&
+ if (lastcomp + 1 == rsp->gpnum &&
+ lastcomp == rsp->completed &&
rsp->signaled == signaled) {
rsp->signaled = RCU_FORCE_QS;
rsp->completed_fqs = lastcomp;

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