linux-kernel - Re: list-debug variants of rcu list routines.

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Date:	Thu, 15 Mar 2012 09:08:15 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Dave Jones <davej@...hat.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: list-debug variants of rcu list routines.

On Wed, Mar 14, 2012 at 10:17:39PM -0400, Dave Jones wrote:
> * Make __list_add_rcu check the next->prev and prev->next pointers
>   just like __list_add does.
> * Make list_del_rcu use __list_del_entry, which does the same checking
>   at deletion time.
> 
> Has been running for a week here without anything being tripped up,
> but it seems worth adding for completeness just in case something
> ever does corrupt those lists.

Queued, thank you!

							Thanx, Paul

> Signed-off-by: Dave Jones <davej@...hat.com>
> 
> diff -durpN '--exclude-from=/home/davej/.exclude' -u src/git-trees/kernel/linux/include/linux/rculist.h linux-dj/include/linux/rculist.h
> --- src/git-trees/kernel/linux/include/linux/rculist.h	2011-07-23 00:05:34.000000000 -0400
> +++ linux-dj/include/linux/rculist.h	2012-03-07 00:21:47.050583527 -0500
> @@ -30,6 +30,7 @@
>   * This is only for internal list manipulation where we know
>   * the prev/next entries already!
>   */
> +#ifndef CONFIG_DEBUG_LIST
>  static inline void __list_add_rcu(struct list_head *new,
>  		struct list_head *prev, struct list_head *next)
>  {
> @@ -38,6 +39,10 @@ static inline void __list_add_rcu(struct
>  	rcu_assign_pointer(list_next_rcu(prev), new);
>  	next->prev = new;
>  }
> +#else
> +extern void __list_add_rcu(struct list_head *new,
> +		struct list_head *prev, struct list_head *next);
> +#endif
> 
>  /**
>   * list_add_rcu - add a new entry to rcu-protected list
> @@ -108,7 +113,7 @@ static inline void list_add_tail_rcu(str
>   */
>  static inline void list_del_rcu(struct list_head *entry)
>  {
> -	__list_del(entry->prev, entry->next);
> +	__list_del_entry(entry);
>  	entry->prev = LIST_POISON2;
>  }
> 
> diff -durpN '--exclude-from=/home/davej/.exclude' -u src/git-trees/kernel/linux/lib/list_debug.c linux-dj/lib/list_debug.c
> --- src/git-trees/kernel/linux/lib/list_debug.c	2011-02-19 12:00:40.000000000 -0500
> +++ linux-dj/lib/list_debug.c	2012-03-07 00:18:12.108062540 -0500
> @@ -8,6 +8,7 @@
> 
>  #include <linux/module.h>
>  #include <linux/list.h>
> +#include <linux/rculist.h>
> 
>  /*
>   * Insert a new entry between two known consecutive entries.
> @@ -73,3 +74,24 @@ void list_del(struct list_head *entry)
>  	entry->prev = LIST_POISON2;
>  }
>  EXPORT_SYMBOL(list_del);
> +
> +/*
> + * RCU variants.
> + */
> +void __list_add_rcu(struct list_head *new,
> +                struct list_head *prev, struct list_head *next)
> +{
> +	WARN(next->prev != prev,
> +		"list_add_rcu corruption. next->prev should be "
> +		"prev (%p), but was %p. (next=%p).\n",
> +		prev, next->prev, next);
> +	WARN(prev->next != next,
> +		"list_add_rcu corruption. prev->next should be "
> +		"next (%p), but was %p. (prev=%p).\n",
> +		next, prev->next, prev);
> +        new->next = next;
> +        new->prev = prev;
> +        rcu_assign_pointer(list_next_rcu(prev), new);
> +        next->prev = new;
> +}
> +EXPORT_SYMBOL(__list_add_rcu);
> 

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