diff --git a/sys/kern/sysv_shm.c b/sys/kern/sysv_shm.c
index 056386b05fa6..0095b14a7350 100644
--- a/sys/kern/sysv_shm.c
+++ b/sys/kern/sysv_shm.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: sysv_shm.c,v 1.140 2019/10/09 17:44:45 chs Exp $	*/
+/*	$NetBSD: sysv_shm.c,v 1.141 2019/10/09 17:47:13 chs Exp $	*/
 
 /*-
  * Copyright (c) 1999, 2007 The NetBSD Foundation, Inc.
@@ -61,7 +61,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: sysv_shm.c,v 1.140 2019/10/09 17:44:45 chs Exp $");
+__KERNEL_RCSID(0, "$NetBSD: sysv_shm.c,v 1.141 2019/10/09 17:47:13 chs Exp $");
 
 #ifdef _KERNEL_OPT
 #include "opt_sysv.h"
@@ -437,42 +437,30 @@ sys_shmat(struct lwp *l, const struct sys_shmat_args *uap, register_t *retval)
 
 	/*
 	 * Create a map entry, add it to the list and increase the counters.
-	 * The lock will be dropped before the mapping, disable reallocation.
 	 */
 	shmmap_s = shmmap_getprivate(p);
 	SLIST_INSERT_HEAD(&shmmap_s->entries, shmmap_se, next);
 	shmmap_s->nitems++;
 	shmseg->shm_lpid = p->p_pid;
 	shmseg->shm_nattch++;
-	shm_realloc_disable++;
 
 	/*
-	 * Add a reference to the uvm object while we hold the
-	 * shm_lock.
+	 * Map the segment into the address space.
 	 */
 	uobj = shmseg->_shm_internal;
 	uao_reference(uobj);
-	mutex_exit(&shm_lock);
-
-	/*
-	 * Drop the shm_lock to map it into the address space, and lock
-	 * the memory, if needed (XXX where does this lock memory?).
-	 */
 	error = uvm_map(&vm->vm_map, &attach_va, size, uobj, 0, 0,
 	    UVM_MAPFLAG(prot, prot, UVM_INH_SHARE, UVM_ADV_RANDOM, flags));
 	if (error)
 		goto err_detach;
 
 	/* Set the new address, and update the time */
-	mutex_enter(&shm_lock);
 	shmmap_se->va = attach_va;
 	shmseg->shm_atime = time_second;
-	shm_realloc_disable--;
 	retval[0] = attach_va;
 	SHMPRINTF(("shmat: vm %p: add %d @%lx\n",
 	    p->p_vmspace, shmmap_se->shmid, attach_va));
 err:
-	cv_broadcast(&shm_realloc_cv);
 	mutex_exit(&shm_lock);
 	if (error && shmmap_se) {
 		kmem_free(shmmap_se, sizeof(struct shmmap_entry));
@@ -481,10 +469,7 @@ err:
 
 err_detach:
 	uao_detach(uobj);
-	mutex_enter(&shm_lock);
 	uobj = shm_delete_mapping(shmmap_s, shmmap_se);
-	shm_realloc_disable--;
-	cv_broadcast(&shm_realloc_cv);
 	mutex_exit(&shm_lock);
 	if (uobj != NULL) {
 		uao_detach(uobj);