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Fix the phys_pager in the way similar to the rev. 1.83 of the

Browse Source 
sys/vm/device_pager.c:

Protect the creation of the phys pager with non-NULL handle with the
phys_pager_mtx. Lookup of phys pager in the pagers list by handle is now
synchronized with its removal from the list, and phys_pager_mtx is put
before vm object lock in lock order. Dispose the phys_pager_alloc_lock
and tsleep calls, together with acquiring Giant, since phys_pager_mtx
now covers the same block.

Reviewed by:	alc
Approved by:	re (kensmith)
This commit is contained in:
Konstantin Belousov 2007-08-18 16:40:33 +00:00
parent 11eeea5e85
commit efe7553ed7
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=171887
1 changed files with 25 additions and 22 deletions
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47
sys/vm/phys_pager.c
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@ -42,8 +42,6 @@ __FBSDID("$FreeBSD$");
#include <vm/vm_page.h>
#include <vm/vm_pager.h>
/* prevent concurrent creation races */
static int phys_pager_alloc_lock;
/* list of device pager objects */
static struct pagerlst phys_pager_object_list;
/* protect access to phys_pager_object_list */
@ -64,7 +62,7 @@ static vm_object_t
phys_pager_alloc(void *handle, vm_ooffset_t size, vm_prot_t prot,
vm_ooffset_t foff)
{
vm_object_t object;
vm_object_t object, object1;
vm_pindex_t pindex;
/*
@ -76,38 +74,41 @@ phys_pager_alloc(void *handle, vm_ooffset_t size, vm_prot_t prot,
pindex = OFF_TO_IDX(foff + PAGE_MASK + size);
if (handle != NULL) {
mtx_lock(&Giant);
/*
* Lock to prevent object creation race condition.
*/
while (phys_pager_alloc_lock) {
phys_pager_alloc_lock = -1;
tsleep(&phys_pager_alloc_lock, PVM, "swpalc", 0);
}
phys_pager_alloc_lock = 1;
mtx_lock(&phys_pager_mtx);
/*
* Look up pager, creating as necessary.
*/
object1 = NULL;
object = vm_pager_object_lookup(&phys_pager_object_list, handle);
if (object == NULL) {
/*
* Allocate object and associate it with the pager.
*/
object = vm_object_allocate(OBJT_PHYS, pindex);
object->handle = handle;
mtx_lock(&phys_pager_mtx);
TAILQ_INSERT_TAIL(&phys_pager_object_list, object,
pager_object_list);
mtx_unlock(&phys_pager_mtx);
object1 = vm_object_allocate(OBJT_PHYS, pindex);
mtx_lock(&phys_pager_mtx);
object = vm_pager_object_lookup(&phys_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_INSERT_TAIL(&phys_pager_object_list, object,
pager_object_list);
}
} else {
if (pindex > object->size)
object->size = pindex;
}
if (phys_pager_alloc_lock == -1)
wakeup(&phys_pager_alloc_lock);
phys_pager_alloc_lock = 0;
mtx_unlock(&Giant);
mtx_unlock(&phys_pager_mtx);
vm_object_deallocate(object1);
} else {
object = vm_object_allocate(OBJT_PHYS, pindex);
}
@ -123,9 +124,11 @@ phys_pager_dealloc(vm_object_t object)
{
if (object->handle != NULL) {
VM_OBJECT_UNLOCK(object);
mtx_lock(&phys_pager_mtx);
TAILQ_REMOVE(&phys_pager_object_list, object, pager_object_list);
mtx_unlock(&phys_pager_mtx);
VM_OBJECT_LOCK(object);
}
}