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Commit cb1e78cf authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcu: Remove ACCESS_ONCE() from jiffies 



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: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: default avatarJosh Triplett <josh@joshtriplett.org>
parent 87de1cfd

kernel/rcu/torture.c

+2 −2
Original line number Diff line number Diff line
@@ -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");

kernel/rcu/tree.c

+3 −3
Original line number Diff line number Diff line
@@ -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.