[Patch v2] rcu: update the CONFIG logic in include/linux/pagemap.h

[Patch v2] rcu: update the CONFIG logic in include/linux/pagemap.h

[Amerigo Wang]

TREE_RCU depends on !PREEMPT && SMP, when !CONFIG_SMP is true, CONFIG_TREE_RCU
will be false, thus "!defined(CONFIG_SMP) && defined(CONFIG_TREE_RCU)"
is always false.

Paul suggested to update the logic to
!defined(CONFIG_SMP) && defined(CONFIG_TREE_PREEMPT_RCU).

Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: WANG Cong <amwang@redhat.com>

---
 include/linux/pagemap.h |    9 +++------
 1 files changed, 3 insertions(+), 6 deletions(-)

diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index c119506..a296d7c 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -133,10 +133,9 @@ static inline int page_cache_get_speculative(struct page *page)
 {
 	VM_BUG_ON(in_interrupt());
 
-#if !defined(CONFIG_SMP) && defined(CONFIG_TREE_RCU)
-# ifdef CONFIG_PREEMPT
+#if !defined(CONFIG_SMP) && defined(CONFIG_TREE_PREEMPT_RCU)
+	/* Must have CONFIG_PREEMPT here, implied by CONFIG_TREE_PREEMPT_RCU. */
 	VM_BUG_ON(!in_atomic());
-# endif
 	/*
 	 * Preempt must be disabled here - we rely on rcu_read_lock doing
 	 * this for us.
@@ -171,10 +170,8 @@ static inline int page_cache_add_speculative(struct page *page, int count)
 {
 	VM_BUG_ON(in_interrupt());
 
-#if !defined(CONFIG_SMP) && defined(CONFIG_TREE_RCU)
-# ifdef CONFIG_PREEMPT
+#if !defined(CONFIG_SMP) && defined(CONFIG_TREE_PREEMPT_RCU)
 	VM_BUG_ON(!in_atomic());
-# endif
 	VM_BUG_ON(page_count(page) == 0);
 	atomic_add(count, &page->_count);
 

Re: [Patch v2] rcu: update the CONFIG logic in include/linux/pagemap.h

[Paul E. McKenney]

On Wed, Apr 06, 2011 at 02:32:48PM +0800, Amerigo Wang wrote:
> TREE_RCU depends on !PREEMPT && SMP, when !CONFIG_SMP is true, CONFIG_TREE_RCU
> will be false, thus "!defined(CONFIG_SMP) && defined(CONFIG_TREE_RCU)"
> is always false.
> 
> Paul suggested to update the logic to
> !defined(CONFIG_SMP) && defined(CONFIG_TREE_PREEMPT_RCU).

Hello, Amerigo,

Thank you for keeping on top of this one!

But how does this patch handle the #else clauses?

							Thanx, Paul

> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> Signed-off-by: WANG Cong <amwang@redhat.com>
> 
> ---
>  include/linux/pagemap.h |    9 +++------
>  1 files changed, 3 insertions(+), 6 deletions(-)
> 
> diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
> index c119506..a296d7c 100644
> --- a/include/linux/pagemap.h
> +++ b/include/linux/pagemap.h
> @@ -133,10 +133,9 @@ static inline int page_cache_get_speculative(struct page *page)
>  {
>  	VM_BUG_ON(in_interrupt());
> 
> -#if !defined(CONFIG_SMP) && defined(CONFIG_TREE_RCU)
> -# ifdef CONFIG_PREEMPT
> +#if !defined(CONFIG_SMP) && defined(CONFIG_TREE_PREEMPT_RCU)
> +	/* Must have CONFIG_PREEMPT here, implied by CONFIG_TREE_PREEMPT_RCU. */
>  	VM_BUG_ON(!in_atomic());
> -# endif
>  	/*
>  	 * Preempt must be disabled here - we rely on rcu_read_lock doing
>  	 * this for us.
> @@ -171,10 +170,8 @@ static inline int page_cache_add_speculative(struct page *page, int count)
>  {
>  	VM_BUG_ON(in_interrupt());
> 
> -#if !defined(CONFIG_SMP) && defined(CONFIG_TREE_RCU)
> -# ifdef CONFIG_PREEMPT
> +#if !defined(CONFIG_SMP) && defined(CONFIG_TREE_PREEMPT_RCU)
>  	VM_BUG_ON(!in_atomic());
> -# endif
>  	VM_BUG_ON(page_count(page) == 0);
>  	atomic_add(count, &page->_count);
>