From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: linux-kernel@vger.kernel.org
Cc: mingo@kernel.org, laijs@cn.fujitsu.com, dipankar@in.ibm.com,
akpm@linux-foundation.org, mathieu.desnoyers@efficios.com,
josh@joshtriplett.org, niv@us.ibm.com, tglx@linutronix.de,
peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com,
edumazet@google.com, darren@dvhart.com, fweisbec@gmail.com,
oleg@redhat.com, sbw@mit.edu,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Subject: [PATCH tip/core/rcu 01/12] rcu: Add ACCESS_ONCE() to ->n_force_qs_lh accesses
Date: Mon, 17 Feb 2014 13:35:48 -0800 [thread overview]
Message-ID: <1392672959-6386-1-git-send-email-paulmck@linux.vnet.ibm.com> (raw)
In-Reply-To: <20140217213533.GA5387@linux.vnet.ibm.com>
From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
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>
---
kernel/rcu/tree.c | 4 ++--
kernel/rcu/tree_trace.c | 2 +-
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");
--
1.8.1.5
next prev parent reply other threads:[~2014-02-17 21:36 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-02-17 21:35 [PATCH tip/core/rcu 0/12] Miscellaneous fixes for 3.15 Paul E. McKenney
2014-02-17 21:35 ` Paul E. McKenney [this message]
2014-02-17 21:35 ` [PATCH tip/core/rcu 02/12] rcu: Stop tracking FSF's postal address Paul E. McKenney
2014-02-17 21:35 ` [PATCH tip/core/rcu 03/12] rcu: Remove ACCESS_ONCE() from jiffies Paul E. McKenney
2014-02-17 21:35 ` [PATCH tip/core/rcu 04/12] rcu: Glue ASCII strings together Paul E. McKenney
2014-02-17 21:35 ` [PATCH tip/core/rcu 05/12] rcu: Indentation and spacing fixes Paul E. McKenney
2014-02-17 21:35 ` [PATCH tip/core/rcu 06/12] rcu: Define rcu_assign_pointer() in terms of smp_store_release() Paul E. McKenney
2014-02-17 21:35 ` [PATCH tip/core/rcu 07/12] rcu: Disambiguate CONFIG_RCU_NOCB_CPUs Paul E. McKenney
2014-02-17 21:35 ` [PATCH tip/core/rcu 08/12] rcu: Move SRCU grace period work to power efficient workqueue Paul E. McKenney
2014-02-17 21:35 ` [PATCH tip/core/rcu 09/12] fs: Substitute rcu_access_pointer() for rcu_dereference_raw() Paul E. McKenney
2014-02-17 22:00 ` Josh Triplett
2014-02-17 23:05 ` Paul E. McKenney
2014-02-18 0:04 ` Josh Triplett
2014-02-18 0:27 ` Paul E. McKenney
2014-02-17 21:35 ` [PATCH tip/core/rcu 10/12] block: " Paul E. McKenney
2014-02-18 20:21 ` Jens Axboe
2014-02-17 21:35 ` [PATCH tip/core/rcu 11/12] notifier: " Paul E. McKenney
2014-02-17 21:35 ` [PATCH tip/core/rcu 12/12] rcu: Fix sparse warning for rcu_expedited from kernel/ksysfs.c Paul E. McKenney
2014-02-17 22:01 ` [PATCH tip/core/rcu 0/12] Miscellaneous fixes for 3.15 Josh Triplett
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