From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx179.postini.com [74.125.245.179]) by kanga.kvack.org (Postfix) with SMTP id 3DD056B005D for ; Thu, 26 Jul 2012 14:21:54 -0400 (EDT) Message-ID: <50118182.8030308@redhat.com> Date: Thu, 26 Jul 2012 13:42:26 -0400 From: Rik van Riel MIME-Version: 1.0 Subject: Re: [PATCH -alternative] mm: hugetlbfs: Close race during teardown of hugetlbfs shared page tables V2 (resend) References: <20120720134937.GG9222@suse.de> <20120720141108.GH9222@suse.de> <20120720143635.GE12434@tiehlicka.suse.cz> <20120720145121.GJ9222@suse.de> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Hugh Dickins Cc: Mel Gorman , Michal Hocko , Linux-MM , David Gibson , Ken Chen , Cong Wang , LKML , Larry Woodman On 07/23/2012 12:04 AM, Hugh Dickins wrote: > Please don't be upset if I say that I don't like either of your patches. > Mainly for obvious reasons - I don't like Mel's because anything with > trylock retries and nested spinlocks worries me before I can even start > to think about it; and I don't like Michal's for the same reason as Mel, > that it spreads more change around in common paths than we would like. I have a naive question. In huge_pmd_share, we protect ourselves by taking the mapping->i_mmap_mutex. Is there any reason we could not take the i_mmap_mutex in the huge_pmd_unshare path? I see that hugetlb_change_protection already takes that lock. Is there something preventing __unmap_hugepage_range from also taking mapping->i_mmap_mutex? That way the sharing and the unsharing code are protected by the same, per shm segment, 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