diff options
Diffstat (limited to 'db2/mutex')
| -rw-r--r-- | db2/mutex/README | 8 | ||||
| -rw-r--r-- | db2/mutex/mutex.c | 16 |
2 files changed, 8 insertions, 16 deletions
diff --git a/db2/mutex/README b/db2/mutex/README index 30d6b6a..fceeef7 100644 --- a/db2/mutex/README +++ b/db2/mutex/README @@ -1,4 +1,4 @@ -# @(#)README 10.1 (Sleepycat) 4/12/97 +# @(#)README 10.2 (Sleepycat) 11/25/97 Resource locking routines: lock based on a db_mutex_t. All this gunk (including trying to make assembly code portable), is necessary because @@ -11,9 +11,9 @@ information. If HAVE_SPINLOCKS is defined (i.e. we know how to do test-and-sets for this compiler/architecture combination), we try and lock the resource tsl -TSL_DEFAULT_SPINS times. If we can't acquire the lock that way, we use -a system call to sleep for 10ms, 20ms, 40ms, etc. (The time is bounded -at 1 second, just in case.) Using the timer backoff means that there are +__db_tsl_spins times. If we can't acquire the lock that way, we use a +system call to sleep for 10ms, 20ms, 40ms, etc. (The time is bounded at +1 second, just in case.) Using the timer backoff means that there are two assumptions: that locks are held for brief periods (never over system calls or I/O) and that locks are not hotly contested. diff --git a/db2/mutex/mutex.c b/db2/mutex/mutex.c index 7c8ea6e..6e87c5f 100644 --- a/db2/mutex/mutex.c +++ b/db2/mutex/mutex.c @@ -8,7 +8,7 @@ #include "config.h" #ifndef lint -static const char sccsid[] = "@(#)mutex.c 10.28 (Sleepycat) 10/31/97"; +static const char sccsid[] = "@(#)mutex.c 10.29 (Sleepycat) 11/25/97"; #endif /* not lint */ #ifndef NO_SYSTEM_INCLUDES @@ -101,12 +101,6 @@ static const char sccsid[] = "@(#)mutex.c 10.28 (Sleepycat) 10/31/97"; #endif /* HAVE_SPINLOCKS */ -#ifdef MORE_THAN_ONE_PROCESSOR -#define TSL_DEFAULT_SPINS 5 /* Default spins before block. */ -#else -#define TSL_DEFAULT_SPINS 1 /* Default spins before block. */ -#endif - /* * __db_mutex_init -- * Initialize a DB mutex structure. @@ -130,6 +124,7 @@ __db_mutex_init(mp, off) #ifdef HAVE_SPINLOCKS TSL_INIT(&mp->tsl_resource); + mp->spins = __os_spin(); #else mp->off = off; #endif @@ -155,11 +150,8 @@ __db_mutex_lock(mp, fd) int nspins; for (usecs = MS(10);;) { - /* - * Try and acquire the uncontested resource lock for - * TSL_DEFAULT_SPINS. - */ - for (nspins = TSL_DEFAULT_SPINS; nspins > 0; --nspins) + /* Try and acquire the uncontested resource lock for N spins. */ + for (nspins = mp->spins; nspins > 0; --nspins) if (TSL_SET(&mp->tsl_resource)) { #ifdef DEBUG if (mp->pid != 0) { |