Date: Thu, 24 May 2012 04:09:48 +0000 (UTC) From: Alan Cox <alc@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-9@freebsd.org Subject: svn commit: r235878 - stable/9/sys/vm Message-ID: <201205240409.q4O49mDA014338@svn.freebsd.org>
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Author: alc Date: Thu May 24 04:09:47 2012 New Revision: 235878 URL: http://svn.freebsd.org/changeset/base/235878 Log: MFC r232160 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. Modified: stable/9/sys/vm/vm_map.c Directory Properties: stable/9/sys/ (props changed) Modified: stable/9/sys/vm/vm_map.c ============================================================================== --- stable/9/sys/vm/vm_map.c Thu May 24 03:45:13 2012 (r235877) +++ stable/9/sys/vm/vm_map.c Thu May 24 04:09:47 2012 (r235878) @@ -3087,27 +3087,25 @@ 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; @@ -3228,15 +3226,13 @@ 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);
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