From: Ingo Molnar Subject: Re: 2.6.25-git2: BUG: unable to handle kernel paging request at ffffffffffffffff Date: Mon, 21 Apr 2008 15:00:22 +0200 Message-ID: <20080421130022.GH9554@elte.hu> References: <200804191522.54334.rjw@sisk.pl> <200804202104.24037.rjw@sisk.pl> <20080421011855.GA6243@gondor.apana.org.au> <20080421020806.GL20138@linux.vnet.ibm.com> <20080421045911.GA1812@linux.vnet.ibm.com> <20080421054729.GA19864@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Herbert Xu , Linus Torvalds , "Rafael J. Wysocki" , LKML , Andrew Morton , linux-ext4@vger.kernel.org To: "Paul E. McKenney" Return-path: Content-Disposition: inline In-Reply-To: <20080421054729.GA19864@linux.vnet.ibm.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org * Paul E. McKenney wrote: > On Sun, Apr 20, 2008 at 09:59:11PM -0700, Paul E. McKenney wrote: > > And here is an update with one bug fixed -- testing continues. > > This is an update of http://lkml.org/lkml/2008/4/20/217, deleting > > list_for_each_safe_rcu() and fixing hlist_for_each_entry_rcu(). > > Testing continues... > > And it passes. i have queued up your patch in its form below. (but Linus might beat me at applying it) Ingo --------------------> Subject: RCU, list.h: fix list iterators From: "Paul E. McKenney" Date: Sun, 20 Apr 2008 21:59:13 -0700 RCU list iterators: should prefetch ever be optimised out with no side-effects, the current version will lose the barrier completely. Pointed-out-by: Linus Torvalds Signed-off-by: Paul E. McKenney Signed-off-by: Ingo Molnar --- include/linux/list.h | 48 +++++++++++++++--------------------------------- 1 file changed, 15 insertions(+), 33 deletions(-) Index: linux/include/linux/list.h =================================================================== --- linux.orig/include/linux/list.h +++ linux/include/linux/list.h @@ -631,31 +631,14 @@ static inline void list_splice_init_rcu( * as long as the traversal is guarded by rcu_read_lock(). */ #define list_for_each_rcu(pos, head) \ - for (pos = (head)->next; \ - prefetch(rcu_dereference(pos)->next), pos != (head); \ - pos = pos->next) + for (pos = rcu_dereference((head)->next); \ + prefetch(pos->next), pos != (head); \ + pos = rcu_dereference(pos->next)) #define __list_for_each_rcu(pos, head) \ - for (pos = (head)->next; \ - rcu_dereference(pos) != (head); \ - pos = pos->next) - -/** - * list_for_each_safe_rcu - * @pos: the &struct list_head to use as a loop cursor. - * @n: another &struct list_head to use as temporary storage - * @head: the head for your list. - * - * Iterate over an rcu-protected list, safe against removal of list entry. - * - * This list-traversal primitive may safely run concurrently with - * the _rcu list-mutation primitives such as list_add_rcu() - * as long as the traversal is guarded by rcu_read_lock(). - */ -#define list_for_each_safe_rcu(pos, n, head) \ - for (pos = (head)->next; \ - n = rcu_dereference(pos)->next, pos != (head); \ - pos = n) + for (pos = rcu_dereference((head)->next); \ + pos != (head); \ + pos = rcu_dereference(pos->next)) /** * list_for_each_entry_rcu - iterate over rcu list of given type @@ -668,10 +651,9 @@ static inline void list_splice_init_rcu( * as long as the traversal is guarded by rcu_read_lock(). */ #define list_for_each_entry_rcu(pos, head, member) \ - for (pos = list_entry((head)->next, typeof(*pos), member); \ - prefetch(rcu_dereference(pos)->member.next), \ - &pos->member != (head); \ - pos = list_entry(pos->member.next, typeof(*pos), member)) + for (pos = list_entry(rcu_dereference((head)->next), typeof(*pos), member); \ + prefetch(pos->member.next), &pos->member != (head); \ + pos = list_entry(rcu_dereference(pos->member.next), typeof(*pos), member)) /** @@ -686,9 +668,9 @@ static inline void list_splice_init_rcu( * as long as the traversal is guarded by rcu_read_lock(). */ #define list_for_each_continue_rcu(pos, head) \ - for ((pos) = (pos)->next; \ - prefetch(rcu_dereference((pos))->next), (pos) != (head); \ - (pos) = (pos)->next) + for ((pos) = rcu_dereference((pos)->next); \ + prefetch((pos)->next), (pos) != (head); \ + (pos) = rcu_dereference((pos)->next)) /* * Double linked lists with a single pointer list head. @@ -986,10 +968,10 @@ static inline void hlist_add_after_rcu(s * as long as the traversal is guarded by rcu_read_lock(). */ #define hlist_for_each_entry_rcu(tpos, pos, head, member) \ - for (pos = (head)->first; \ - rcu_dereference(pos) && ({ prefetch(pos->next); 1;}) && \ + for (pos = rcu_dereference((head)->first); \ + pos && ({ prefetch(pos->next); 1;}) && \ ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \ - pos = pos->next) + pos = rcu_dereference(pos->next)) #else #warning "don't include kernel headers in userspace"