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Protect the creation of the device pager with the dev_pager_mtx. Lookup

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of device pager in the pagers list by handle is now synchronized with
its removal from the list, and dev_pager_mtx is put before vm object
lock in lock order. Dispose the dev_pager_sx lock, since dev_pager_mtx
now covers the same block.

Noted by:	kensmith
Reviewed by:	alc
Approved by:	re (kensmith)
This commit is contained in:
Konstantin Belousov 2007-08-07 15:36:25 +00:00
parent 5a5ee8cb1e
commit deea654ebf
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=171779
1 changed files with 24 additions and 12 deletions
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36
sys/vm/device_pager.c
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@ -64,8 +64,6 @@ static boolean_t dev_pager_haspage(vm_object_t, vm_pindex_t, int *,
/* list of device pager objects */
static struct pagerlst dev_pager_object_list;
/* protect against object creation */
static struct sx dev_pager_sx;
/* protect list manipulation */
static struct mtx dev_pager_mtx;
@ -89,7 +87,6 @@ static void
dev_pager_init()
{
TAILQ_INIT(&dev_pager_object_list);
sx_init(&dev_pager_sx, "dev_pager create");
mtx_init(&dev_pager_mtx, "dev_pager list", NULL, MTX_DEF);
fakepg_zone = uma_zcreate("DP fakepg", sizeof(struct vm_page),
NULL, NULL, NULL, NULL, UMA_ALIGN_PTR,
@ -103,7 +100,7 @@ static vm_object_t
dev_pager_alloc(void *handle, vm_ooffset_t size, vm_prot_t prot, vm_ooffset_t foff)
{
struct cdev *dev;
vm_object_t object;
vm_object_t object, object1;
vm_pindex_t pindex;
unsigned int npages;
vm_paddr_t paddr;
@ -143,29 +140,42 @@ dev_pager_alloc(void *handle, vm_ooffset_t size, vm_prot_t prot, vm_ooffset_t fo
/*
* Lock to prevent object creation race condition.
*/
sx_xlock(&dev_pager_sx);
mtx_lock(&dev_pager_mtx);
/*
* Look up pager, creating as necessary.
*/
object1 = NULL;
object = vm_pager_object_lookup(&dev_pager_object_list, handle);
if (object == NULL) {
/*
* Allocate object and associate it with the pager.
*/
object = vm_object_allocate(OBJT_DEVICE, pindex);
object->handle = handle;
TAILQ_INIT(&object->un_pager.devp.devp_pglist);
mtx_lock(&dev_pager_mtx);
TAILQ_INSERT_TAIL(&dev_pager_object_list, object, pager_object_list);
mtx_unlock(&dev_pager_mtx);
object1 = vm_object_allocate(OBJT_DEVICE, pindex);
mtx_lock(&dev_pager_mtx);
object = vm_pager_object_lookup(&dev_pager_object_list, handle);
if (object != NULL) {
/*
* We raced with other thread while allocating object.
*/
if (pindex > object->size)
object->size = pindex;
} else {
object = object1;
object1 = NULL;
object->handle = handle;
TAILQ_INIT(&object->un_pager.devp.devp_pglist);
TAILQ_INSERT_TAIL(&dev_pager_object_list, object,
pager_object_list);
}
} else {
if (pindex > object->size)
object->size = pindex;
}
sx_xunlock(&dev_pager_sx);
mtx_unlock(&dev_pager_mtx);
dev_relthread(dev);
vm_object_deallocate(object1);
return (object);
}
@ -175,9 +185,11 @@ dev_pager_dealloc(object)
{
vm_page_t m;
VM_OBJECT_UNLOCK(object);
mtx_lock(&dev_pager_mtx);
TAILQ_REMOVE(&dev_pager_object_list, object, pager_object_list);
mtx_unlock(&dev_pager_mtx);
VM_OBJECT_LOCK(object);
/*
* Free up our fake pages.
*/