From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx163.postini.com [74.125.245.163]) by kanga.kvack.org (Postfix) with SMTP id 386596B005C for ; Wed, 30 May 2012 21:57:50 -0400 (EDT) Received: by pbbrp2 with SMTP id rp2so912956pbb.14 for ; Wed, 30 May 2012 18:57:49 -0700 (PDT) Date: Wed, 30 May 2012 18:57:47 -0700 (PDT) From: David Rientjes Subject: Re: [PATCH -V7 05/14] hugetlb: avoid taking i_mmap_mutex in unmap_single_vma() for hugetlb In-Reply-To: <1338388739-22919-6-git-send-email-aneesh.kumar@linux.vnet.ibm.com> Message-ID: References: <1338388739-22919-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <1338388739-22919-6-git-send-email-aneesh.kumar@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: "Aneesh Kumar K.V" Cc: linux-mm@kvack.org, kamezawa.hiroyu@jp.fujitsu.com, dhillf@gmail.com, mhocko@suse.cz, akpm@linux-foundation.org, hannes@cmpxchg.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, Andrea Arcangeli On Wed, 30 May 2012, Aneesh Kumar K.V wrote: > From: "Aneesh Kumar K.V" > > i_mmap_mutex lock was added in unmap_single_vma by 502717f4e ("hugetlb: > fix linked list corruption in unmap_hugepage_range()") but we don't use > page->lru in unmap_hugepage_range any more. Also the lock was taken > higher up in the stack in some code path. That would result in deadlock. > > unmap_mapping_range (i_mmap_mutex) > -> unmap_mapping_range_tree > -> unmap_mapping_range_vma > -> zap_page_range_single > -> unmap_single_vma > -> unmap_hugepage_range (i_mmap_mutex) > You should be able to show this with lockdep? > For shared pagetable support for huge pages, since pagetable pages are ref > counted we don't need any lock during huge_pmd_unshare. We do take > i_mmap_mutex in huge_pmd_share while walking the vma_prio_tree in mapping. > (39dde65c9940c97f ("shared page table for hugetlb page")). > I think this should be folded into patch 4, the code you're removing here is just added in that function unnecessarily. -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org