From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Thu, 28 Feb 2008 15:05:30 -0800 (PST) From: Christoph Lameter Subject: Re: [PATCH] mmu notifiers #v7 In-Reply-To: <20080227192610.GF28483@v2.random> Message-ID: References: <20080219084357.GA22249@wotan.suse.de> <20080219135851.GI7128@v2.random> <20080219231157.GC18912@wotan.suse.de> <20080220010941.GR7128@v2.random> <20080220103942.GU7128@v2.random> <20080221045430.GC15215@wotan.suse.de> <20080221144023.GC9427@v2.random> <20080221161028.GA14220@sgi.com> <20080227192610.GF28483@v2.random> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: Andrea Arcangeli Cc: Jack Steiner , Nick Piggin , akpm@linux-foundation.org, Robin Holt , Avi Kivity , Izik Eidus , kvm-devel@lists.sourceforge.net, Peter Zijlstra , general@lists.openfabrics.org, Steve Wise , Roland Dreier , Kanoj Sarcar , linux-kernel@vger.kernel.org, linux-mm@kvack.org, daniel.blueman@quadrics.com List-ID: On Wed, 27 Feb 2008, Andrea Arcangeli wrote: > +struct mmu_notifier_head { > + struct hlist_head head; > + spinlock_t lock; > +}; Still think that the lock here is not of too much use and can be easily replaced by mmap_sem. > +#define mmu_notifier(function, mm, args...) \ > + do { \ > + struct mmu_notifier *__mn; \ > + struct hlist_node *__n; \ > + \ > + if (unlikely(!hlist_empty(&(mm)->mmu_notifier.head))) { \ > + rcu_read_lock(); \ > + hlist_for_each_entry_rcu(__mn, __n, \ > + &(mm)->mmu_notifier.head, \ > + hlist) \ > + if (__mn->ops->function) \ > + __mn->ops->function(__mn, \ > + mm, \ > + args); \ > + rcu_read_unlock(); \ > + } \ > + } while (0) Andrew recomended local variables for parameters used multile times. This means the mm parameter here. > +/* > + * Notifiers that use the parameters that they were passed so that the > + * compiler does not complain about unused variables but does proper > + * parameter checks even if !CONFIG_MMU_NOTIFIER. > + * Macros generate no code. > + */ > +#define mmu_notifier(function, mm, args...) \ > + do { \ > + if (0) { \ > + struct mmu_notifier *__mn; \ > + \ > + __mn = (struct mmu_notifier *)(0x00ff); \ > + __mn->ops->function(__mn, mm, args); \ > + }; \ > + } while (0) Note also Andrew's comments on the use of 0x00ff... > +/* > + * No synchronization. This function can only be called when only a single > + * process remains that performs teardown. > + */ > +void mmu_notifier_release(struct mm_struct *mm) > +{ > + struct mmu_notifier *mn; > + struct hlist_node *n, *tmp; > + > + if (unlikely(!hlist_empty(&mm->mmu_notifier.head))) { > + hlist_for_each_entry_safe(mn, n, tmp, > + &mm->mmu_notifier.head, hlist) { > + hlist_del(&mn->hlist); > + if (mn->ops->release) > + mn->ops->release(mn, mm); > + } > + } > +} One could avoid a hlist_for_each_entry_safe here by simply always deleting the first object. Also re the _notify variants: The binding to pte_clear_flush_young etc will become a problem for notifiers that want to sleep because pte_clear_flush is usually called with the pte lock held. See f.e. try_to_unmap_one, page_mkclean_one etc. It would be better if the notifier calls could be moved outside of the pte lock. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org