From owner-svn-src-stable-7@FreeBSD.ORG Tue Jan 25 19:44:56 2011 Return-Path: Delivered-To: svn-src-stable-7@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 46D461065697; Tue, 25 Jan 2011 19:44:56 +0000 (UTC) (envelope-from jhb@FreeBSD.org) Received: from svn.freebsd.org (svn.freebsd.org [IPv6:2001:4f8:fff6::2c]) by mx1.freebsd.org (Postfix) with ESMTP id 35E368FC19; Tue, 25 Jan 2011 19:44:56 +0000 (UTC) Received: from svn.freebsd.org (localhost [127.0.0.1]) by svn.freebsd.org (8.14.3/8.14.3) with ESMTP id p0PJiu7I048018; Tue, 25 Jan 2011 19:44:56 GMT (envelope-from jhb@svn.freebsd.org) Received: (from jhb@localhost) by svn.freebsd.org (8.14.3/8.14.3/Submit) id p0PJiuC5048015; Tue, 25 Jan 2011 19:44:56 GMT (envelope-from jhb@svn.freebsd.org) Message-Id: <201101251944.p0PJiuC5048015@svn.freebsd.org> From: John Baldwin Date: Tue, 25 Jan 2011 19:44:56 +0000 (UTC) To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-7@freebsd.org X-SVN-Group: stable-7 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Cc: Subject: svn commit: r217836 - stable/7/sys/vm X-BeenThere: svn-src-stable-7@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: SVN commit messages for only the 7-stable src tree List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 25 Jan 2011 19:44:56 -0000 Author: jhb Date: Tue Jan 25 19:44:55 2011 New Revision: 217836 URL: http://svn.freebsd.org/changeset/base/217836 Log: MFC 214144: - Make 'vm_refcnt' volatile so that compilers won't be tempted to treat its value as a loop invariant. Currently this is a no-op because 'atomic_cmpset_int()' clobbers all memory on current architectures. - Use atomic_fetchadd_int() instead of an atomic_cmpset_int() loop to drop a reference in vmspace_free(). Modified: stable/7/sys/vm/vm_map.c stable/7/sys/vm/vm_map.h Directory Properties: stable/7/sys/ (props changed) stable/7/sys/cddl/contrib/opensolaris/ (props changed) stable/7/sys/contrib/dev/acpica/ (props changed) stable/7/sys/contrib/pf/ (props changed) Modified: stable/7/sys/vm/vm_map.c ============================================================================== --- stable/7/sys/vm/vm_map.c Tue Jan 25 19:44:42 2011 (r217835) +++ stable/7/sys/vm/vm_map.c Tue Jan 25 19:44:55 2011 (r217836) @@ -336,15 +336,11 @@ vmspace_dofree(struct vmspace *vm) void vmspace_free(struct vmspace *vm) { - int refcnt; if (vm->vm_refcnt == 0) panic("vmspace_free: attempt to free already freed vmspace"); - do - refcnt = vm->vm_refcnt; - while (!atomic_cmpset_int(&vm->vm_refcnt, refcnt, refcnt - 1)); - if (refcnt == 1) + if (atomic_fetchadd_int(&vm->vm_refcnt, -1) == 1) vmspace_dofree(vm); } Modified: stable/7/sys/vm/vm_map.h ============================================================================== --- stable/7/sys/vm/vm_map.h Tue Jan 25 19:44:42 2011 (r217835) +++ stable/7/sys/vm/vm_map.h Tue Jan 25 19:44:55 2011 (r217836) @@ -246,7 +246,7 @@ struct vmspace { caddr_t vm_taddr; /* (c) user virtual address of text */ caddr_t vm_daddr; /* (c) user virtual address of data */ caddr_t vm_maxsaddr; /* user VA at max stack growth */ - int vm_refcnt; /* number of references */ + volatile int vm_refcnt; /* number of references */ }; #ifdef _KERNEL