[PATCH] force_quiescent_state: factor out duplicated code

[PATCH] force_quiescent_state: factor out duplicated code

[Oleg Nesterov]

On top of rcu-simplify-improve-batch-tuning.patch

Cleanup. Move '#ifdef CONFIG_SMP' check and rdp->bhlimit setting
into force_quiescent_state().

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>

--- 18-rc6/kernel/rcupdate.c~2_fold	2006-09-10 16:56:10.000000000 +0400
+++ 18-rc6/kernel/rcupdate.c	2006-09-10 20:00:31.000000000 +0400
@@ -76,14 +76,17 @@ static atomic_t rcu_barrier_cpu_count;
 static DEFINE_MUTEX(rcu_barrier_mutex);
 static struct completion rcu_barrier_completion;
 
-#ifdef CONFIG_SMP
 static void force_quiescent_state(struct rcu_data *rdp,
-			struct rcu_ctrlblk *rcp)
+				struct rcu_ctrlblk *rcp)
 {
-	int cpu;
-	cpumask_t cpumask;
+	rdp->blimit = INT_MAX;
 	set_need_resched();
+
+#ifdef CONFIG_SMP
 	if (unlikely(!rcp->signaled)) {
+		cpumask_t cpumask;
+		int cpu;
+
 		rcp->signaled = 1;
 		/*
 		 * Don't send IPI to itself. With irqs disabled,
@@ -94,14 +97,8 @@ static void force_quiescent_state(struct
 		for_each_cpu_mask(cpu, cpumask)
 			smp_send_reschedule(cpu);
 	}
-}
-#else
-static inline void force_quiescent_state(struct rcu_data *rdp,
-			struct rcu_ctrlblk *rcp)
-{
-	set_need_resched();
-}
 #endif
+}
 
 /**
  * call_rcu - Queue an RCU callback for invocation after a grace period.
@@ -126,10 +123,9 @@ void fastcall call_rcu(struct rcu_head *
 	rdp = &__get_cpu_var(rcu_data);
 	*rdp->nxttail = head;
 	rdp->nxttail = &head->next;
-	if (unlikely(++rdp->qlen > qhimark)) {
-		rdp->blimit = INT_MAX;
+
+	if (unlikely(++rdp->qlen > qhimark))
 		force_quiescent_state(rdp, &rcu_ctrlblk);
-	}
 	local_irq_restore(flags);
 }
 
@@ -162,11 +158,8 @@ void fastcall call_rcu_bh(struct rcu_hea
 	*rdp->nxttail = head;
 	rdp->nxttail = &head->next;
 
-	if (unlikely(++rdp->qlen > qhimark)) {
-		rdp->blimit = INT_MAX;
+	if (unlikely(++rdp->qlen > qhimark))
 		force_quiescent_state(rdp, &rcu_bh_ctrlblk);
-	}
-
 	local_irq_restore(flags);
 }
 

Re: [PATCH] force_quiescent_state: factor out duplicated code

[Dipankar Sarma]

On Sun, Sep 10, 2006 at 08:18:10PM +0400, Oleg Nesterov wrote:
> On top of rcu-simplify-improve-batch-tuning.patch
> 
> Cleanup. Move '#ifdef CONFIG_SMP' check and rdp->bhlimit setting
> into force_quiescent_state().


Pushing the rdp->blimit setting into force_quiescent_state is fine,
but I see no need to insert #ifdef CONFIG_SMP into a routine.
Let us continue to have separate versions of force_quiescent_state()
for CONFIG_SMP and !CONFIG_SMP. It looks cleaner with #ifdefs inserted
in between.

Thanks
Dipankar

Re: [PATCH] force_quiescent_state: factor out duplicated code

[Oleg Nesterov]

On 09/11, Dipankar Sarma wrote:
>
> On Sun, Sep 10, 2006 at 08:18:10PM +0400, Oleg Nesterov wrote:
> > On top of rcu-simplify-improve-batch-tuning.patch
> > 
> > Cleanup. Move '#ifdef CONFIG_SMP' check and rdp->bhlimit setting
> > into force_quiescent_state().
> 
> 
> Pushing the rdp->blimit setting into force_quiescent_state is fine,
> but I see no need to insert #ifdef CONFIG_SMP into a routine.

Otherwise we need to push the rdp->blimit setting into both versions
of force_quiescent_state(), for CONFIG_SMP and !CONFIG_SMP.

> Let us continue to have separate versions of force_quiescent_state()
> for CONFIG_SMP and !CONFIG_SMP. It looks cleaner with #ifdefs inserted
> in between.

I personally think exactly opposite :)

Ok, let's forget about this patch, it was only cleanup.

Oleg.