* [PATCH 1/1] rcu: remove remaining read-modify-write ACCESS_ONCE() calls
@ 2014-07-08 21:46 Pranith Kumar
2014-07-08 22:09 ` Paul E. McKenney
0 siblings, 1 reply; 2+ messages in thread
From: Pranith Kumar @ 2014-07-08 21:46 UTC (permalink / raw)
To: Paul E. McKenney, Josh Triplett, open list:READ-COPY UPDATE...
Change the remaining uses of ACCESS_ONCE() so that each ACCESS_ONCE() either does a load or a store, but not both.
Signed-off-by: Pranith Kumar <bobby.prani@gmail.com>
---
kernel/rcu/tree.c | 6 ++++--
kernel/rcu/tree_plugin.h | 8 +++++---
2 files changed, 9 insertions(+), 5 deletions(-)
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index dac6d20..c356bf6 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1700,7 +1700,8 @@ static int rcu_gp_fqs(struct rcu_state *rsp, int fqs_state_in)
if (ACCESS_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) {
raw_spin_lock_irq(&rnp->lock);
smp_mb__after_unlock_lock();
- ACCESS_ONCE(rsp->gp_flags) &= ~RCU_GP_FLAG_FQS;
+ ACCESS_ONCE(rsp->gp_flags) =
+ ACCESS_ONCE(rsp->gp_flags) & ~RCU_GP_FLAG_FQS;
raw_spin_unlock_irq(&rnp->lock);
}
return fqs_state;
@@ -2514,7 +2515,8 @@ static void force_quiescent_state(struct rcu_state *rsp)
raw_spin_unlock_irqrestore(&rnp_old->lock, flags);
return; /* Someone beat us to it. */
}
- ACCESS_ONCE(rsp->gp_flags) |= RCU_GP_FLAG_FQS;
+ ACCESS_ONCE(rsp->gp_flags) =
+ ACCESS_ONCE(rsp->gp_flags) | RCU_GP_FLAG_FQS;
raw_spin_unlock_irqrestore(&rnp_old->lock, flags);
wake_up(&rsp->gp_wq); /* Memory barrier implied by wake_up() path. */
}
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 637a8a9..f87b88c 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -897,7 +897,8 @@ void synchronize_rcu_expedited(void)
/* Clean up and exit. */
smp_mb(); /* ensure expedited GP seen before counter increment. */
- ACCESS_ONCE(sync_rcu_preempt_exp_count)++;
+ ACCESS_ONCE(sync_rcu_preempt_exp_count) =
+ sync_rcu_preempt_exp_count + 1;
unlock_mb_ret:
mutex_unlock(&sync_rcu_preempt_exp_mutex);
mb_ret:
@@ -2307,8 +2308,9 @@ static int rcu_nocb_kthread(void *arg)
list = next;
}
trace_rcu_batch_end(rdp->rsp->name, c, !!list, 0, 0, 1);
- ACCESS_ONCE(rdp->nocb_p_count) -= c;
- ACCESS_ONCE(rdp->nocb_p_count_lazy) -= cl;
+ ACCESS_ONCE(rdp->nocb_p_count) = rdp->nocb_p_count - c;
+ ACCESS_ONCE(rdp->nocb_p_count_lazy) =
+ rdp->nocb_p_count_lazy - cl;
rdp->n_nocbs_invoked += c;
}
return 0;
--
1.9.1
^ permalink raw reply related [flat|nested] 2+ messages in thread* Re: [PATCH 1/1] rcu: remove remaining read-modify-write ACCESS_ONCE() calls
2014-07-08 21:46 [PATCH 1/1] rcu: remove remaining read-modify-write ACCESS_ONCE() calls Pranith Kumar
@ 2014-07-08 22:09 ` Paul E. McKenney
0 siblings, 0 replies; 2+ messages in thread
From: Paul E. McKenney @ 2014-07-08 22:09 UTC (permalink / raw)
To: Pranith Kumar; +Cc: Josh Triplett, open list:READ-COPY UPDATE...
On Tue, Jul 08, 2014 at 05:46:50PM -0400, Pranith Kumar wrote:
> Change the remaining uses of ACCESS_ONCE() so that each ACCESS_ONCE() either does a load or a store, but not both.
>
> Signed-off-by: Pranith Kumar <bobby.prani@gmail.com>
Queued for 3.18, thank you Pranith!
Thanx, Paul
> ---
> kernel/rcu/tree.c | 6 ++++--
> kernel/rcu/tree_plugin.h | 8 +++++---
> 2 files changed, 9 insertions(+), 5 deletions(-)
>
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index dac6d20..c356bf6 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -1700,7 +1700,8 @@ static int rcu_gp_fqs(struct rcu_state *rsp, int fqs_state_in)
> if (ACCESS_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) {
> raw_spin_lock_irq(&rnp->lock);
> smp_mb__after_unlock_lock();
> - ACCESS_ONCE(rsp->gp_flags) &= ~RCU_GP_FLAG_FQS;
> + ACCESS_ONCE(rsp->gp_flags) =
> + ACCESS_ONCE(rsp->gp_flags) & ~RCU_GP_FLAG_FQS;
> raw_spin_unlock_irq(&rnp->lock);
> }
> return fqs_state;
> @@ -2514,7 +2515,8 @@ static void force_quiescent_state(struct rcu_state *rsp)
> raw_spin_unlock_irqrestore(&rnp_old->lock, flags);
> return; /* Someone beat us to it. */
> }
> - ACCESS_ONCE(rsp->gp_flags) |= RCU_GP_FLAG_FQS;
> + ACCESS_ONCE(rsp->gp_flags) =
> + ACCESS_ONCE(rsp->gp_flags) | RCU_GP_FLAG_FQS;
> raw_spin_unlock_irqrestore(&rnp_old->lock, flags);
> wake_up(&rsp->gp_wq); /* Memory barrier implied by wake_up() path. */
> }
> diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
> index 637a8a9..f87b88c 100644
> --- a/kernel/rcu/tree_plugin.h
> +++ b/kernel/rcu/tree_plugin.h
> @@ -897,7 +897,8 @@ void synchronize_rcu_expedited(void)
>
> /* Clean up and exit. */
> smp_mb(); /* ensure expedited GP seen before counter increment. */
> - ACCESS_ONCE(sync_rcu_preempt_exp_count)++;
> + ACCESS_ONCE(sync_rcu_preempt_exp_count) =
> + sync_rcu_preempt_exp_count + 1;
> unlock_mb_ret:
> mutex_unlock(&sync_rcu_preempt_exp_mutex);
> mb_ret:
> @@ -2307,8 +2308,9 @@ static int rcu_nocb_kthread(void *arg)
> list = next;
> }
> trace_rcu_batch_end(rdp->rsp->name, c, !!list, 0, 0, 1);
> - ACCESS_ONCE(rdp->nocb_p_count) -= c;
> - ACCESS_ONCE(rdp->nocb_p_count_lazy) -= cl;
> + ACCESS_ONCE(rdp->nocb_p_count) = rdp->nocb_p_count - c;
> + ACCESS_ONCE(rdp->nocb_p_count_lazy) =
> + rdp->nocb_p_count_lazy - cl;
> rdp->n_nocbs_invoked += c;
> }
> return 0;
> --
> 1.9.1
>
^ permalink raw reply [flat|nested] 2+ messages in thread
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2014-07-08 21:46 [PATCH 1/1] rcu: remove remaining read-modify-write ACCESS_ONCE() calls Pranith Kumar
2014-07-08 22:09 ` Paul E. McKenney
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