From owner-svn-src-all@FreeBSD.ORG Sat Feb 25 17:49:59 2012 Return-Path: Delivered-To: svn-src-all@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id C4D6B106564A; Sat, 25 Feb 2012 17:49:59 +0000 (UTC) (envelope-from alc@FreeBSD.org) Received: from svn.freebsd.org (svn.freebsd.org [IPv6:2001:4f8:fff6::2c]) by mx1.freebsd.org (Postfix) with ESMTP id 96CDD8FC08; Sat, 25 Feb 2012 17:49:59 +0000 (UTC) Received: from svn.freebsd.org (localhost [127.0.0.1]) by svn.freebsd.org (8.14.4/8.14.4) with ESMTP id q1PHnxgx027527; Sat, 25 Feb 2012 17:49:59 GMT (envelope-from alc@svn.freebsd.org) Received: (from alc@localhost) by svn.freebsd.org (8.14.4/8.14.4/Submit) id q1PHnx9E027525; Sat, 25 Feb 2012 17:49:59 GMT (envelope-from alc@svn.freebsd.org) Message-Id: <201202251749.q1PHnx9E027525@svn.freebsd.org> From: Alan Cox Date: Sat, 25 Feb 2012 17:49:59 +0000 (UTC) To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org X-SVN-Group: head MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Cc: Subject: svn commit: r232160 - head/sys/vm X-BeenThere: svn-src-all@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: "SVN commit messages for the entire src tree \(except for " user" and " projects" \)" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 25 Feb 2012 17:49:59 -0000 Author: alc Date: Sat Feb 25 17:49:59 2012 New Revision: 232160 URL: http://svn.freebsd.org/changeset/base/232160 Log: Simplify vmspace_fork()'s control flow by copying immutable data before the vm map locks are acquired. Also, eliminate redundant initialization of the new vm map's timestamp. Reviewed by: kib MFC after: 3 weeks Modified: head/sys/vm/vm_map.c Modified: head/sys/vm/vm_map.c ============================================================================== --- head/sys/vm/vm_map.c Sat Feb 25 16:02:12 2012 (r232159) +++ head/sys/vm/vm_map.c Sat Feb 25 17:49:59 2012 (r232160) @@ -3082,27 +3082,25 @@ struct vmspace * vmspace_fork(struct vmspace *vm1, vm_ooffset_t *fork_charge) { struct vmspace *vm2; - vm_map_t old_map = &vm1->vm_map; - vm_map_t new_map; - vm_map_entry_t old_entry; - vm_map_entry_t new_entry; + vm_map_t new_map, old_map; + vm_map_entry_t new_entry, old_entry; vm_object_t object; int locked; - vm_map_lock(old_map); - if (old_map->busy) - vm_map_wait_busy(old_map); - new_map = NULL; /* silence gcc */ + old_map = &vm1->vm_map; + /* Copy immutable fields of vm1 to vm2. */ vm2 = vmspace_alloc(old_map->min_offset, old_map->max_offset); if (vm2 == NULL) - goto unlock_and_return; + return (NULL); vm2->vm_taddr = vm1->vm_taddr; vm2->vm_daddr = vm1->vm_daddr; vm2->vm_maxsaddr = vm1->vm_maxsaddr; - new_map = &vm2->vm_map; /* XXX */ + vm_map_lock(old_map); + if (old_map->busy) + vm_map_wait_busy(old_map); + new_map = &vm2->vm_map; locked = vm_map_trylock(new_map); /* trylock to silence WITNESS */ KASSERT(locked, ("vmspace_fork: lock failed")); - new_map->timestamp = 1; old_entry = old_map->header.next; @@ -3223,15 +3221,13 @@ vmspace_fork(struct vmspace *vm1, vm_oof } old_entry = old_entry->next; } -unlock_and_return: /* * Use inlined vm_map_unlock() to postpone handling the deferred * map entries, which cannot be done until both old_map and * new_map locks are released. */ sx_xunlock(&old_map->lock); - if (vm2 != NULL) - sx_xunlock(&new_map->lock); + sx_xunlock(&new_map->lock); vm_map_process_deferred(); return (vm2);