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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2013-12-03 09:24:02 -0800
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2014-02-17 15:01:10 -0800
commit3660c2813fb6d0ba48ee44bcbf9feddf7218c11d (patch)
treedb632e8ff7302aae520dfab42e6b2fce4615fb7f
parent6d0abeca3242a88cab8232e4acd7e2bf088f3bc2 (diff)
downloadblackbird-op-linux-3660c2813fb6d0ba48ee44bcbf9feddf7218c11d.tar.gz
blackbird-op-linux-3660c2813fb6d0ba48ee44bcbf9feddf7218c11d.zip
rcu: Add ACCESS_ONCE() to ->n_force_qs_lh accesses
The ->n_force_qs_lh field is accessed without the benefit of any synchronization, so this commit adds the needed ACCESS_ONCE() wrappers. Yes, increments to ->n_force_qs_lh can be lost, but contention should be low and the field is strictly statistical in nature, so this is not a problem. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
-rw-r--r--kernel/rcu/tree.c4
-rw-r--r--kernel/rcu/tree_trace.c2
2 files changed, 3 insertions, 3 deletions
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index b3d116cd072d..e64157798624 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -2304,7 +2304,7 @@ static void force_quiescent_state(struct rcu_state *rsp)
if (rnp_old != NULL)
raw_spin_unlock(&rnp_old->fqslock);
if (ret) {
- rsp->n_force_qs_lh++;
+ ACCESS_ONCE(rsp->n_force_qs_lh)++;
return;
}
rnp_old = rnp;
@@ -2316,7 +2316,7 @@ static void force_quiescent_state(struct rcu_state *rsp)
smp_mb__after_unlock_lock();
raw_spin_unlock(&rnp_old->fqslock);
if (ACCESS_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) {
- rsp->n_force_qs_lh++;
+ ACCESS_ONCE(rsp->n_force_qs_lh)++;
raw_spin_unlock_irqrestore(&rnp_old->lock, flags);
return; /* Someone beat us to it. */
}
diff --git a/kernel/rcu/tree_trace.c b/kernel/rcu/tree_trace.c
index 4def475336d4..d1f1e64a6d72 100644
--- a/kernel/rcu/tree_trace.c
+++ b/kernel/rcu/tree_trace.c
@@ -273,7 +273,7 @@ static void print_one_rcu_state(struct seq_file *m, struct rcu_state *rsp)
seq_printf(m, "nfqs=%lu/nfqsng=%lu(%lu) fqlh=%lu oqlen=%ld/%ld\n",
rsp->n_force_qs, rsp->n_force_qs_ngp,
rsp->n_force_qs - rsp->n_force_qs_ngp,
- rsp->n_force_qs_lh, rsp->qlen_lazy, rsp->qlen);
+ ACCESS_ONCE(rsp->n_force_qs_lh), rsp->qlen_lazy, rsp->qlen);
for (rnp = &rsp->node[0]; rnp - &rsp->node[0] < rcu_num_nodes; rnp++) {
if (rnp->level != level) {
seq_puts(m, "\n");
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