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Update locking comment above vm_page:

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- re-assign page queue lock "Q"
       - assign page lock "P"
       - update several uncommented fields
       - observe that hold_count is now protected by the page lock "P"
This commit is contained in:
Kip Macy 2010-05-01 03:41:21 +00:00
parent 483191871b
commit 0ce3ba8cd5
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=207460
1 changed files with 10 additions and 9 deletions
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19
sys/vm/vm_page.h
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@ -90,20 +90,21 @@
* and sundry status bits.
*
* Fields in this structure are locked either by the lock on the
* object that the page belongs to (O) or by the lock on the page
* queues (P).
* object that the page belongs to (O), its corresponding page lock (P),
* or by the lock on the page queues (Q).
*
*/
TAILQ_HEAD(pglist, vm_page);
struct vm_page {
TAILQ_ENTRY(vm_page) pageq; /* queue info for FIFO queue or free list (P) */
TAILQ_ENTRY(vm_page) pageq; /* queue info for FIFO queue or free list (Q) */
TAILQ_ENTRY(vm_page) listq; /* pages in same object (O) */
struct vm_page *left; /* splay tree link (O) */
struct vm_page *right; /* splay tree link (O) */
vm_object_t object; /* which object am I in (O,P)*/
vm_pindex_t pindex; /* offset into object (O,P) */
vm_object_t object; /* which object am I in (O,Q)*/
vm_pindex_t pindex; /* offset into object (O,Q) */
vm_paddr_t phys_addr; /* physical address of page */
struct md_page md; /* machine dependant stuff */
uint8_t queue; /* page queue index */
@ -111,11 +112,11 @@ struct vm_page {
u_short flags; /* see below */
uint8_t order; /* index of the buddy queue */
uint8_t pool;
u_short cow; /* page cow mapping count */
u_int wire_count; /* wired down maps refs (P) */
short hold_count; /* page hold count */
u_short cow; /* page cow mapping count (Q) */
u_int wire_count; /* wired down maps refs (Q) */
short hold_count; /* page hold count (P) */
u_short oflags; /* page flags (O) */
u_char act_count; /* page usage count */
u_char act_count; /* page usage count (Q) */
u_char busy; /* page busy count (O) */
/* NOTE that these must support one bit per DEV_BSIZE in a page!!! */
/* so, on normal X86 kernels, they must be at least 8 bits wide */