Module Name: src
Committed By: chs
Date: Wed Oct 9 17:44:45 UTC 2019
Modified Files:
src/sys/kern: sysv_shm.c
Log Message:
revert rev 1.139 (fixing a race between shmat() and shmdt())
that approach turned out to be too complicated.
To generate a diff of this commit:
cvs rdiff -u -r1.139 -r1.140 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:1.139 src/sys/kern/sysv_shm.c:1.140
--- src/sys/kern/sysv_shm.c:1.139 Tue Oct 1 16:36:58 2019
+++ src/sys/kern/sysv_shm.c Wed Oct 9 17:44:45 2019
@@ -1,4 +1,4 @@
-/* $NetBSD: sysv_shm.c,v 1.139 2019/10/01 16:36:58 chs Exp $ */
+/* $NetBSD: sysv_shm.c,v 1.140 2019/10/09 17:44:45 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 1.139 2019/10/01 16:36:58 chs Exp $");
+__KERNEL_RCSID(0, "$NetBSD: sysv_shm.c,v 1.140 2019/10/09 17:44:45 chs Exp $");
#ifdef _KERNEL_OPT
#include "opt_sysv.h"
@@ -87,7 +87,6 @@ struct shmmap_entry {
SLIST_ENTRY(shmmap_entry) next;
vaddr_t va;
int shmid;
- bool busy;
};
int shm_nused __cacheline_aligned;
@@ -314,10 +313,8 @@ sys_shmdt(struct lwp *l, const struct sy
struct uvm_object *uobj;
struct shmid_ds *shmseg;
size_t size;
- int segnum;
mutex_enter(&shm_lock);
-restart:
/* In case of reallocation, we will wait for completion */
while (__predict_false(shm_realloc_state))
cv_wait(&shm_realloc_cv, &shm_lock);
@@ -349,18 +346,12 @@ restart:
}
}
- segnum = IPCID_TO_IX(shmmap_se->shmid);
- if (shmmap_se->busy) {
- cv_wait(&shm_cv[segnum], &shm_lock);
- goto restart;
- }
-
SHMPRINTF(("shmdt: vm %p: remove %d @%lx\n",
p->p_vmspace, shmmap_se->shmid, shmmap_se->va));
/* Delete the entry from shm map */
uobj = shm_delete_mapping(shmmap_s, shmmap_se);
- shmseg = &shmsegs[segnum];
+ shmseg = &shmsegs[IPCID_TO_IX(shmmap_se->shmid)];
size = (shmseg->shm_segsz + PGOFSET) & ~PGOFSET;
mutex_exit(&shm_lock);
@@ -395,13 +386,10 @@ sys_shmat(struct lwp *l, const struct sy
vaddr_t attach_va;
vm_prot_t prot;
vsize_t size;
- int segnum;
/* Allocate a new map entry and set it */
shmmap_se = kmem_alloc(sizeof(struct shmmap_entry), KM_SLEEP);
shmmap_se->shmid = SCARG(uap, shmid);
- shmmap_se->busy = true;
- segnum = IPCID_TO_IX(shmmap_se->shmid);
mutex_enter(&shm_lock);
/* In case of reallocation, we will wait for completion */
@@ -478,13 +466,11 @@ sys_shmat(struct lwp *l, const struct sy
/* Set the new address, and update the time */
mutex_enter(&shm_lock);
shmmap_se->va = attach_va;
- shmmap_se->busy = false;
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));
- cv_broadcast(&shm_cv[segnum]);
err:
cv_broadcast(&shm_realloc_cv);
mutex_exit(&shm_lock);
@@ -498,7 +484,6 @@ err_detach:
mutex_enter(&shm_lock);
uobj = shm_delete_mapping(shmmap_s, shmmap_se);
shm_realloc_disable--;
- cv_broadcast(&shm_cv[segnum]);
cv_broadcast(&shm_realloc_cv);
mutex_exit(&shm_lock);
if (uobj != NULL) {
