Module Name: src
Committed By: chs
Date: Wed Oct 9 17:47:13 UTC 2019
Modified Files:
src/sys/kern: sysv_shm.c
Log Message:
simpler fix for the race between shmat() and shmdt():
change shmat() to hold shm_lock until it is completely done.
To generate a diff of this commit:
cvs rdiff -u -r1.140 -r1.141 src/sys/kern/sysv_shm.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/kern/sysv_shm.c
diff -u src/sys/kern/sysv_shm.c:1.140 src/sys/kern/sysv_shm.c:1.141
--- src/sys/kern/sysv_shm.c:1.140 Wed Oct 9 17:44:45 2019
+++ src/sys/kern/sysv_shm.c Wed Oct 9 17:47:13 2019
@@ -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 sy
/*
* 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);
