From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f197.google.com (mail-pf0-f197.google.com [209.85.192.197]) by kanga.kvack.org (Postfix) with ESMTP id 41EE36B03A7 for ; Mon, 17 Apr 2017 19:45:43 -0400 (EDT) Received: by mail-pf0-f197.google.com with SMTP id q25so93532674pfg.6 for ; Mon, 17 Apr 2017 16:45:43 -0700 (PDT) Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com. [148.163.156.1]) by mx.google.com with ESMTPS id z27si12623623pfj.235.2017.04.17.16.45.42 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 17 Apr 2017 16:45:42 -0700 (PDT) Received: from pps.filterd (m0098394.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.20/8.16.0.20) with SMTP id v3HNjS4W068396 for ; Mon, 17 Apr 2017 19:45:42 -0400 Received: from e13.ny.us.ibm.com (e13.ny.us.ibm.com [129.33.205.203]) by mx0a-001b2d01.pphosted.com with ESMTP id 29w26abst1-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Mon, 17 Apr 2017 19:45:41 -0400 Received: from localhost by e13.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 17 Apr 2017 19:45:40 -0400 From: "Paul E. McKenney" Subject: [PATCH v2 tip/core/rcu 34/39] mm: Use static initialization for "srcu" Date: Mon, 17 Apr 2017 16:45:21 -0700 In-Reply-To: <20170417234452.GB19013@linux.vnet.ibm.com> References: <20170417234452.GB19013@linux.vnet.ibm.com> Message-Id: <1492472726-3841-34-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, bobby.prani@gmail.com, "Paul E. McKenney" , linux-mm@kvack.org, Michal Hocko , Vegard Nossum The MM-notifier code currently dynamically initializes the srcu_struct named "srcu" at subsys_initcall() time, and includes a BUG_ON() to check this initialization in do_mmu_notifier_register(). Unfortunately, there is no foolproof way to verify that an srcu_struct has been initialized, given the possibility of an srcu_struct being allocated on the stack or on the heap. This means that creating an srcu_struct_is_initialized() function is not a reasonable course of action. Nor is peppering do_mmu_notifier_register() with SRCU-specific #ifdefs an attractive alternative. This commit therefore uses DEFINE_STATIC_SRCU() to initialize this srcu_struct at compile time, thus eliminating both the subsys_initcall()-time initialization and the runtime BUG_ON(). Signed-off-by: Paul E. McKenney Cc: Cc: Andrew Morton Cc: Ingo Molnar Cc: Michal Hocko Cc: "Peter Zijlstra (Intel)" Cc: Vegard Nossum --- mm/mmu_notifier.c | 14 +------------- 1 file changed, 1 insertion(+), 13 deletions(-) diff --git a/mm/mmu_notifier.c b/mm/mmu_notifier.c index a7652acd2ab9..54ca54562928 100644 --- a/mm/mmu_notifier.c +++ b/mm/mmu_notifier.c @@ -21,7 +21,7 @@ #include /* global SRCU for all MMs */ -static struct srcu_struct srcu; +DEFINE_STATIC_SRCU(srcu); /* * This function allows mmu_notifier::release callback to delay a call to @@ -252,12 +252,6 @@ static int do_mmu_notifier_register(struct mmu_notifier *mn, BUG_ON(atomic_read(&mm->mm_users) <= 0); - /* - * Verify that mmu_notifier_init() already run and the global srcu is - * initialized. - */ - BUG_ON(!srcu.per_cpu_ref); - ret = -ENOMEM; mmu_notifier_mm = kmalloc(sizeof(struct mmu_notifier_mm), GFP_KERNEL); if (unlikely(!mmu_notifier_mm)) @@ -406,9 +400,3 @@ void mmu_notifier_unregister_no_release(struct mmu_notifier *mn, mmdrop(mm); } EXPORT_SYMBOL_GPL(mmu_notifier_unregister_no_release); - -static int __init mmu_notifier_init(void) -{ - return init_srcu_struct(&srcu); -} -subsys_initcall(mmu_notifier_init); -- 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