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-rw-r--r--db2/include/mp.h41
1 files changed, 22 insertions, 19 deletions
diff --git a/db2/include/mp.h b/db2/include/mp.h
index 3b71774..f68f42b 100644
--- a/db2/include/mp.h
+++ b/db2/include/mp.h
@@ -4,7 +4,7 @@
* Copyright (c) 1996, 1997
* Sleepycat Software. All rights reserved.
*
- * @(#)mp.h 10.16 (Sleepycat) 9/23/97
+ * @(#)mp.h 10.19 (Sleepycat) 10/25/97
*/
struct __bh; typedef struct __bh BH;
@@ -22,30 +22,36 @@ struct __mpoolfile; typedef struct __mpoolfile MPOOLFILE;
#define DB_CACHESIZE_DEF (128 * 1024)
#define DB_CACHESIZE_MIN ( 20 * 1024)
-/* Macro to return per-process address, offsets. */
-#define ADDR(base, offset) ((void *)((u_int8_t *)((base)->addr) + offset))
-#define OFFSET(base, p) ((u_int8_t *)(p) - (u_int8_t *)(base)->addr)
-
#define INVALID 0 /* Invalid shared memory offset. */
#define TEMPORARY "<tmp>" /* Temporary file name. */
/*
- * There are two kinds of locks in the mpool code. The first is the region
- * lock, used to serialize modifications to all data structures. The second
- * is a per-buffer header lock. The locking order is as follows:
+ * There are three ways we do locking in the mpool code:
+ *
+ * Locking a handle mutex to provide concurrency for DB_THREAD operations.
+ * Locking the region mutex to provide mutual exclusion while reading and
+ * writing structures in the shared region.
+ * Locking buffer header mutexes during I/O.
+ *
+ * The first will not be further described here. We use the shared mpool
+ * region lock to provide mutual exclusion while reading/modifying all of
+ * the data structures, including the buffer headers. We use a per-buffer
+ * header lock to wait on buffer I/O. The order of locking is as follows:
*
- * Process searching for a buffer:
+ * Searching for a buffer:
* Acquire the region lock.
* Find the buffer header.
* Increment the reference count (guarantee the buffer stays).
- * If the BH_LOCKED flag is set:
+ * If the BH_LOCKED flag is set (I/O is going on):
* Release the region lock.
+ * Request the buffer lock.
+ * The I/O will complete...
* Acquire the buffer lock.
* Release the buffer lock.
* Acquire the region lock.
* Return the buffer.
*
- * Process reading/writing a buffer:
+ * Reading/writing a buffer:
* Acquire the region lock.
* Find/create the buffer header.
* If reading, increment the reference count (guarantee the buffer stays).
@@ -69,8 +75,7 @@ struct __mpoolfile; typedef struct __mpoolfile MPOOLFILE;
#define LOCKHANDLE(dbmp, mutexp) \
if (F_ISSET(dbmp, MP_LOCKHANDLE)) \
- (void)__db_mutex_lock(mutexp, (dbmp)->fd, \
- (dbmp)->dbenv == NULL ? NULL : (dbmp)->dbenv->db_yield)
+ (void)__db_mutex_lock(mutexp, (dbmp)->fd)
#define UNLOCKHANDLE(dbmp, mutexp) \
if (F_ISSET(dbmp, MP_LOCKHANDLE)) \
(void)__db_mutex_unlock(mutexp, (dbmp)->fd)
@@ -78,8 +83,7 @@ struct __mpoolfile; typedef struct __mpoolfile MPOOLFILE;
#define LOCKREGION(dbmp) \
if (F_ISSET(dbmp, MP_LOCKREGION)) \
(void)__db_mutex_lock(&((RLAYOUT *)(dbmp)->mp)->lock, \
- (dbmp)->fd, \
- (dbmp)->dbenv == NULL ? NULL : (dbmp)->dbenv->db_yield)
+ (dbmp)->fd)
#define UNLOCKREGION(dbmp) \
if (F_ISSET(dbmp, MP_LOCKREGION)) \
(void)__db_mutex_unlock(&((RLAYOUT *)(dbmp)->mp)->lock, \
@@ -87,8 +91,7 @@ struct __mpoolfile; typedef struct __mpoolfile MPOOLFILE;
#define LOCKBUFFER(dbmp, bhp) \
if (F_ISSET(dbmp, MP_LOCKREGION)) \
- (void)__db_mutex_lock(&(bhp)->mutex, (dbmp)->fd, \
- (dbmp)->dbenv == NULL ? NULL : (dbmp)->dbenv->db_yield)
+ (void)__db_mutex_lock(&(bhp)->mutex, (dbmp)->fd)
#define UNLOCKBUFFER(dbmp, bhp) \
if (F_ISSET(dbmp, MP_LOCKREGION)) \
(void)__db_mutex_unlock(&(bhp)->mutex, (dbmp)->fd)
@@ -250,8 +253,8 @@ struct __bh {
#define BH_WRITE 0x020 /* Page scheduled for writing. */
u_int16_t flags;
- SH_TAILQ_ENTRY q; /* LRU list of bucket headers. */
- SH_TAILQ_ENTRY mq; /* MPOOLFILE list of bucket headers. */
+ SH_TAILQ_ENTRY q; /* LRU queue. */
+ SH_TAILQ_ENTRY hq; /* MPOOL hash bucket queue. */
db_pgno_t pgno; /* Underlying MPOOLFILE page number. */
size_t mf_offset; /* Associated MPOOLFILE offset. */