Author: alc
Date: Tue May 11 01:29:18 2010
New Revision: 207905
URL: http://svn.freebsd.org/changeset/base/207905
Log:
Update synchronization annotations for struct vm_page. Add a comment
explaining how the setting of PG_WRITEABLE is synchronized.
Modified:
head/sys/vm/vm_page.h
Modified: head/sys/vm/vm_page.h
==============================================================================
--- head/sys/vm/vm_page.h Mon May 10 22:21:08 2010 (r207904)
+++ head/sys/vm/vm_page.h Tue May 11 01:29:18 2010 (r207905)
@@ -112,7 +112,7 @@ 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 (Q) */
+ u_short cow; /* page cow mapping count (P) */
u_int wire_count; /* wired down maps refs (P) */
short hold_count; /* page hold count (P) */
u_short oflags; /* page flags (O) */
@@ -122,16 +122,16 @@ struct vm_page {
/* so, on normal X86 kernels, they must be at least 8 bits wide */
#if PAGE_SIZE == 4096
u_char valid; /* map of valid DEV_BSIZE chunks (O) */
- u_char dirty; /* map of dirty DEV_BSIZE chunks */
+ u_char dirty; /* map of dirty DEV_BSIZE chunks (O) */
#elif PAGE_SIZE == 8192
u_short valid; /* map of valid DEV_BSIZE chunks (O) */
- u_short dirty; /* map of dirty DEV_BSIZE chunks */
+ u_short dirty; /* map of dirty DEV_BSIZE chunks (O) */
#elif PAGE_SIZE == 16384
u_int valid; /* map of valid DEV_BSIZE chunks (O) */
- u_int dirty; /* map of dirty DEV_BSIZE chunks */
+ u_int dirty; /* map of dirty DEV_BSIZE chunks (O) */
#elif PAGE_SIZE == 32768
u_long valid; /* map of valid DEV_BSIZE chunks (O) */
- u_long dirty; /* map of dirty DEV_BSIZE chunks */
+ u_long dirty; /* map of dirty DEV_BSIZE chunks (O) */
#endif
};
@@ -216,6 +216,9 @@ extern struct vpglocks pa_lock[];
* via the object/vm_page_t because there is no knowledge of their
* pte mappings, nor can they be removed from their objects via
* the object, and such pages are also not on any PQ queue.
+ *
+ * PG_WRITEABLE is set exclusively by pmap_enter(). When it does so, either
+ * the page must be VPO_BUSY or the containing object must be locked.
*/
#define PG_CACHED 0x0001 /* page is cached */
#define PG_FREE 0x0002 /* page is free */
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