From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Paul E. McKenney" Subject: [PATCH RFC tip/core/rcu 09/15] uprobes: Remove now-redundant smp_read_barrier_depends() Date: Mon, 9 Oct 2017 17:22:43 -0700 Message-ID: <1507594969-8347-9-git-send-email-paulmck@linux.vnet.ibm.com> References: <20171010001951.GA6476@linux.vnet.ibm.com> Return-path: Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:51830 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1755725AbdJJAWz (ORCPT ); Mon, 9 Oct 2017 20:22:55 -0400 Received: from pps.filterd (m0098413.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.21/8.16.0.21) with SMTP id v9A0JPnW109685 for ; Mon, 9 Oct 2017 20:22:54 -0400 Received: from e16.ny.us.ibm.com (e16.ny.us.ibm.com [129.33.205.206]) by mx0b-001b2d01.pphosted.com with ESMTP id 2dggmafayd-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Mon, 09 Oct 2017 20:22:54 -0400 Received: from localhost by e16.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 9 Oct 2017 20:22:53 -0400 In-Reply-To: <20171010001951.GA6476@linux.vnet.ibm.com> Sender: linux-arch-owner@vger.kernel.org List-ID: To: linux-kernel@vger.kernel.org Cc: mingo@kernel.org, torvalds@linux-foundation.org, mark.rutland@arm.com, dhowells@redhat.com, linux-arch@vger.kernel.org, peterz@infradead.org, will.deacon@arm.com, "Paul E. McKenney" , Ingo Molnar , Arnaldo Carvalho de Melo , Alexander Shishkin Now that READ_ONCE() implies smp_read_barrier_depends(), the get_xol_area() and get_trampoline_vaddr() no longer need their smp_read_barrier_depends() calls, which this commit removes. While we are here, convert the corresponding smp_wmb() to an smp_store_release(). Signed-off-by: Paul E. McKenney Cc: Peter Zijlstra Cc: Ingo Molnar Cc: Arnaldo Carvalho de Melo Cc: Alexander Shishkin --- kernel/events/uprobes.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index 267f6ef91d97..ce6848e46e94 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -1167,8 +1167,8 @@ static int xol_add_vma(struct mm_struct *mm, struct xol_area *area) } ret = 0; - smp_wmb(); /* pairs with get_xol_area() */ - mm->uprobes_state.xol_area = area; + /* pairs with get_xol_area() */ + smp_store_release(&mm->uprobes_state.xol_area, area); /* ^^^ */ fail: up_write(&mm->mmap_sem); @@ -1230,8 +1230,8 @@ static struct xol_area *get_xol_area(void) if (!mm->uprobes_state.xol_area) __create_xol_area(0); - area = mm->uprobes_state.xol_area; - smp_read_barrier_depends(); /* pairs with wmb in xol_add_vma() */ + /* Pairs with xol_add_vma() smp_store_release() */ + area = READ_ONCE(mm->uprobes_state.xol_area); /* ^^^ */ return area; } @@ -1528,8 +1528,8 @@ static unsigned long get_trampoline_vaddr(void) struct xol_area *area; unsigned long trampoline_vaddr = -1; - area = current->mm->uprobes_state.xol_area; - smp_read_barrier_depends(); + /* Pairs with xol_add_vma() smp_store_release() */ + area = READ_ONCE(current->mm->uprobes_state.xol_area); /* ^^^ */ if (area) trampoline_vaddr = area->vaddr; -- 2.5.2