From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk0-f199.google.com (mail-qk0-f199.google.com [209.85.220.199]) by kanga.kvack.org (Postfix) with ESMTP id 7B65A6B0038 for ; Fri, 1 Dec 2017 14:51:29 -0500 (EST) Received: by mail-qk0-f199.google.com with SMTP id m67so7187553qkl.8 for ; Fri, 01 Dec 2017 11:51:29 -0800 (PST) Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com. [148.163.156.1]) by mx.google.com with ESMTPS id o59si7411680qte.6.2017.12.01.11.51.27 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 01 Dec 2017 11:51:28 -0800 (PST) Received: from pps.filterd (m0098396.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.21/8.16.0.21) with SMTP id vB1JpDvV116911 for ; Fri, 1 Dec 2017 14:51:27 -0500 Received: from e18.ny.us.ibm.com (e18.ny.us.ibm.com [129.33.205.208]) by mx0a-001b2d01.pphosted.com with ESMTP id 2ekd5e96sk-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Fri, 01 Dec 2017 14:51:26 -0500 Received: from localhost by e18.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Fri, 1 Dec 2017 14:51:25 -0500 From: "Paul E. McKenney" Subject: [PATCH tip/core/rcu 13/21] mm/ksm: Remove now-redundant smp_read_barrier_depends() Date: Fri, 1 Dec 2017 11:51:08 -0800 In-Reply-To: <20171201195053.GA23494@linux.vnet.ibm.com> References: <20171201195053.GA23494@linux.vnet.ibm.com> Message-Id: <1512157876-24665-13-git-send-email-paulmck@linux.vnet.ibm.com> Sender: owner-linux-mm@kvack.org List-ID: To: linux-kernel@vger.kernel.org Cc: mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, fweisbec@gmail.com, oleg@redhat.com, "Paul E. McKenney" , Andrea Arcangeli , Minchan Kim , Michal Hocko , "Kirill A. Shutemov" , "Aneesh Kumar K.V" , Claudio Imbrenda , linux-mm@kvack.org Because READ_ONCE() now implies smp_read_barrier_depends(), the smp_read_barrier_depends() in get_ksm_page() is now redundant. This commit removes it and updates the comments. Signed-off-by: Paul E. McKenney Cc: Andrew Morton Cc: Andrea Arcangeli Cc: Minchan Kim Cc: Michal Hocko Cc: "Kirill A. Shutemov" Cc: Ingo Molnar Cc: "Aneesh Kumar K.V" Cc: Claudio Imbrenda Cc: --- mm/ksm.c | 9 +-------- 1 file changed, 1 insertion(+), 8 deletions(-) diff --git a/mm/ksm.c b/mm/ksm.c index be8f4576f842..c406f75957ad 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -675,15 +675,8 @@ static struct page *get_ksm_page(struct stable_node *stable_node, bool lock_it) expected_mapping = (void *)((unsigned long)stable_node | PAGE_MAPPING_KSM); again: - kpfn = READ_ONCE(stable_node->kpfn); + kpfn = READ_ONCE(stable_node->kpfn); /* Address dependency. */ page = pfn_to_page(kpfn); - - /* - * page is computed from kpfn, so on most architectures reading - * page->mapping is naturally ordered after reading node->kpfn, - * but on Alpha we need to be more careful. - */ - smp_read_barrier_depends(); if (READ_ONCE(page->mapping) != expected_mapping) goto stale; -- 2.5.2 -- 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