Messages in this thread Patch in this message | | | Date | Fri, 7 Mar 2008 20:47:28 +0100 | From | Andrea Arcangeli <> | Subject | Re: [PATCH] 3/4 combine RCU with seqlock to allow mmu notifier methods to sleep (#v9 was 1/4) |
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On Fri, Mar 07, 2008 at 07:45:52PM +0100, Andrea Arcangeli wrote: > On Fri, Mar 07, 2008 at 07:01:35PM +0100, Peter Zijlstra wrote: > > The reason Christoph can do without RCU is because he doesn't allow > > unregister, and as soon as you drop that you'll end up with something > > Not sure to follow, what do you mean "he doesn't allow"? We'll also > have to rip unregister regardless after you pointed out the ->release > won't be called after calling my mmu_notifier_unregister in 3/4. If > you figured out how to retain mmu_notifier_unregister I'm not seeing > it anymore.
Given I don't see other (buggy ;) ways anymore to retain mmu_notifier_unregister, I did like in EMM and I dropped the unregister function.
To me it looks like this will be enough and equally efficient as the expanded version in EMM that is not using the highlevel hlist_rcu macros. If you can see any pitfall let me know! Thanks a lot for the help.
------ This is a replacement for the previously posted 3/4, one of the pieces to allow the mmu notifier methods to sleep.
Signed-off-by: Andrea Arcangeli <andrea@qumranet.com>
diff --git a/include/linux/mmu_notifier.h b/include/linux/mmu_notifier.h --- a/include/linux/mmu_notifier.h +++ b/include/linux/mmu_notifier.h @@ -70,17 +70,6 @@ static inline int mm_has_notifiers(struc */ extern void mmu_notifier_register(struct mmu_notifier *mn, struct mm_struct *mm); -/* - * Must hold the mmap_sem for write. - * - * RCU is used to traverse the list. A quiescent period needs to pass - * before the "struct mmu_notifier" can be freed. Alternatively it - * can be synchronously freed inside ->release when the list can't - * change anymore and nobody could possibly walk it. - */ -extern void mmu_notifier_unregister(struct mmu_notifier *mn, - struct mm_struct *mm); - extern void __mmu_notifier_release(struct mm_struct *mm); extern int __mmu_notifier_clear_flush_young(struct mm_struct *mm, unsigned long address); diff --git a/mm/mmu_notifier.c b/mm/mmu_notifier.c --- a/mm/mmu_notifier.c +++ b/mm/mmu_notifier.c @@ -43,12 +43,10 @@ int __mmu_notifier_clear_flush_young(str struct hlist_node *n; int young = 0; - rcu_read_lock(); hlist_for_each_entry_rcu(mn, n, &mm->mmu_notifier_list, hlist) { if (mn->ops->clear_flush_young) young |= mn->ops->clear_flush_young(mn, mm, address); } - rcu_read_unlock(); return young; } @@ -59,12 +57,10 @@ void __mmu_notifier_invalidate_page(stru struct mmu_notifier *mn; struct hlist_node *n; - rcu_read_lock(); hlist_for_each_entry_rcu(mn, n, &mm->mmu_notifier_list, hlist) { if (mn->ops->invalidate_page) mn->ops->invalidate_page(mn, mm, address); } - rcu_read_unlock(); } void __mmu_notifier_invalidate_range_begin(struct mm_struct *mm, @@ -73,12 +69,10 @@ void __mmu_notifier_invalidate_range_beg struct mmu_notifier *mn; struct hlist_node *n; - rcu_read_lock(); hlist_for_each_entry_rcu(mn, n, &mm->mmu_notifier_list, hlist) { if (mn->ops->invalidate_range_begin) mn->ops->invalidate_range_begin(mn, mm, start, end); } - rcu_read_unlock(); } void __mmu_notifier_invalidate_range_end(struct mm_struct *mm, @@ -87,12 +81,10 @@ void __mmu_notifier_invalidate_range_end struct mmu_notifier *mn; struct hlist_node *n; - rcu_read_lock(); hlist_for_each_entry_rcu(mn, n, &mm->mmu_notifier_list, hlist) { if (mn->ops->invalidate_range_end) mn->ops->invalidate_range_end(mn, mm, start, end); } - rcu_read_unlock(); } /* @@ -106,9 +98,3 @@ void mmu_notifier_register(struct mmu_no hlist_add_head_rcu(&mn->hlist, &mm->mmu_notifier_list); } EXPORT_SYMBOL_GPL(mmu_notifier_register); - -void mmu_notifier_unregister(struct mmu_notifier *mn, struct mm_struct *mm) -{ - hlist_del_rcu(&mn->hlist); -} -EXPORT_SYMBOL_GPL(mmu_notifier_unregister);
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