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rcu: Remove remaining read-modify-write ACCESS_ONCE() calls 

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>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Pranith Kumar 2014-07-08 17:46:50 -04:00 committed by Paul E. McKenney
parent 11ed7f934c
commit 4de376a1b1
2 changed files with 9 additions and 5 deletions
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6
kernel/rcu/tree.c
View File

@ -1684,7 +1684,8 @@ 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;
@ -2505,7 +2506,8 @@ 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. */
}

8
kernel/rcu/tree_plugin.h
View File

@ -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:
@ -2428,8 +2429,9 @@ 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;