diff options
Diffstat (limited to 'db2/include/mp.h')
| -rw-r--r-- | db2/include/mp.h | 33 |
1 files changed, 21 insertions, 12 deletions
diff --git a/db2/include/mp.h b/db2/include/mp.h index f108246..4efbf9b 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 10.22 (Sleepycat) 11/28/97 + * @(#)mp.h 10.25 (Sleepycat) 1/8/98 */ struct __bh; typedef struct __bh BH; @@ -41,13 +41,17 @@ struct __mpoolfile; typedef struct __mpoolfile MPOOLFILE; * Acquire the region lock. * Find the buffer header. * Increment the reference count (guarantee the buffer stays). - * 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. + * While the BH_LOCKED flag is set (I/O is going on) { + * Release the region lock. + * Explicitly yield the processor if it's not the first pass + * through this loop, otherwise, we can simply spin because + * we'll be simply switching between the two locks. + * Request the buffer lock. + * The I/O will complete... + * Acquire the buffer lock. + * Release the buffer lock. + * Acquire the region lock. + * } * Return the buffer. * * Reading/writing a buffer: @@ -57,12 +61,16 @@ struct __mpoolfile; typedef struct __mpoolfile MPOOLFILE; * Set the BH_LOCKED flag. * Acquire the buffer lock (guaranteed not to block). * Release the region lock. - * Do the I/O and/or initialize buffer contents. + * Do the I/O and/or initialize the buffer contents. + * Release the buffer lock. + * At this point, the buffer lock is available, but the logical + * operation (flagged by BH_LOCKED) is not yet completed. For + * this reason, among others, threads checking the BH_LOCKED flag + * must loop around their test. * Acquire the region lock. * Clear the BH_LOCKED flag. * Release the region lock. - * Release the buffer lock. - * If reading, return the buffer. + * Return/discard the buffer. * * Pointers to DB_MPOOL, MPOOL, DB_MPOOLFILE and MPOOLFILE structures are not * reacquired when a region lock is reacquired because they couldn't have been @@ -70,7 +78,8 @@ struct __mpoolfile; typedef struct __mpoolfile MPOOLFILE; */ #define LOCKINIT(dbmp, mutexp) \ if (F_ISSET(dbmp, MP_LOCKHANDLE | MP_LOCKREGION)) \ - (void)__db_mutex_init(mutexp, (dbmp)->fd) + (void)__db_mutex_init(mutexp, \ + MUTEX_LOCK_OFFSET((dbmp)->maddr, mutexp)) #define LOCKHANDLE(dbmp, mutexp) \ if (F_ISSET(dbmp, MP_LOCKHANDLE)) \ |