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 03/12] rcu: Remove ACCESS_ONCE() from jiffies
Date: Mon, 17 Feb 2014 13:35:50 -0800 [thread overview]
Message-ID: <1392672959-6386-3-git-send-email-paulmck@linux.vnet.ibm.com> (raw)
In-Reply-To: <1392672959-6386-1-git-send-email-paulmck@linux.vnet.ibm.com>
From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Because jiffies is one of a very few variables marked "volatile", there
is no need to use ACCESS_ONCE() when accessing it. This commit therefore
removes the redundant ACCESS_ONCE() wrappers.
Reported by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
kernel/rcu/torture.c | 4 ++--
kernel/rcu/tree.c | 6 +++---
2 files changed, 5 insertions(+), 5 deletions(-)
diff --git a/kernel/rcu/torture.c b/kernel/rcu/torture.c
index ab7dd192a50b..022c5312b725 100644
--- a/kernel/rcu/torture.c
+++ b/kernel/rcu/torture.c
@@ -1352,7 +1352,7 @@ rcu_torture_shutdown(void *arg)
unsigned long jiffies_snap;
VERBOSE_PRINTK_STRING("rcu_torture_shutdown task started");
- jiffies_snap = ACCESS_ONCE(jiffies);
+ jiffies_snap = jiffies;
while (ULONG_CMP_LT(jiffies_snap, shutdown_time) &&
!kthread_should_stop()) {
delta = shutdown_time - jiffies_snap;
@@ -1361,7 +1361,7 @@ rcu_torture_shutdown(void *arg)
"rcu_torture_shutdown task: %lu jiffies remaining\n",
torture_type, delta);
schedule_timeout_interruptible(delta);
- jiffies_snap = ACCESS_ONCE(jiffies);
+ jiffies_snap = jiffies;
}
if (kthread_should_stop()) {
VERBOSE_PRINTK_STRING("rcu_torture_shutdown task stopping");
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 321feef0f5c0..73c3cd2b87ac 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -837,7 +837,7 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp,
* to the next. Only do this for the primary flavor of RCU.
*/
if (rdp->rsp == rcu_state &&
- ULONG_CMP_GE(ACCESS_ONCE(jiffies), rdp->rsp->jiffies_resched)) {
+ ULONG_CMP_GE(jiffies, rdp->rsp->jiffies_resched)) {
rdp->rsp->jiffies_resched += 5;
resched_cpu(rdp->cpu);
}
@@ -847,7 +847,7 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp,
static void record_gp_stall_check_time(struct rcu_state *rsp)
{
- unsigned long j = ACCESS_ONCE(jiffies);
+ unsigned long j = jiffies;
unsigned long j1;
rsp->gp_start = j;
@@ -1005,7 +1005,7 @@ static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp)
if (rcu_cpu_stall_suppress || !rcu_gp_in_progress(rsp))
return;
- j = ACCESS_ONCE(jiffies);
+ j = jiffies;
/*
* Lots of memory barriers to reject false positives.
--
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 ` [PATCH tip/core/rcu 01/12] rcu: Add ACCESS_ONCE() to ->n_force_qs_lh accesses Paul E. McKenney
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 ` Paul E. McKenney [this message]
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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