Major update for pthreads, based in large part on improvements

from glibc 2.3.  This should make threads much more efficient.
 -Erik

1 files changed, 124 insertions, 8 deletions

diff --git a/libpthread/linuxthreads/spinlock.h b/libpthread/linuxthreads/spinlock.h
index aae18a27b..0ec40c57c 100644
--- a/libpthread/linuxthreads/spinlock.h
+++ b/libpthread/linuxthreads/spinlock.h
@@ -12,6 +12,27 @@
 /* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the        */
 /* GNU Library General Public License for more details.                 */
 
+#include <bits/initspin.h>
+
+
+/* There are 2 compare and swap synchronization primitives with
+   different semantics:
+
+	1. compare_and_swap, which has acquire semantics (i.e. it
+	completes befor subsequent writes.)
+	2. compare_and_swap_with_release_semantics, which has release
+	semantics (it completes after previous writes.)
+
+   For those platforms on which they are the same. HAS_COMPARE_AND_SWAP
+   should be defined. For those platforms on which they are different,
+   HAS_COMPARE_AND_SWAP_WITH_RELEASE_SEMANTICS has to be defined.  */
+
+#ifndef HAS_COMPARE_AND_SWAP
+#ifdef HAS_COMPARE_AND_SWAP_WITH_RELEASE_SEMANTICS
+#define HAS_COMPARE_AND_SWAP
+#endif
+#endif
+
 #if defined(TEST_FOR_COMPARE_AND_SWAP)
 
 extern int __pthread_has_cas;
@@ -29,6 +50,22 @@ static inline int compare_and_swap(long * ptr, long oldval, long newval,
 
 #elif defined(HAS_COMPARE_AND_SWAP)
 
+#ifdef IMPLEMENT_TAS_WITH_CAS
+#define testandset(p) !__compare_and_swap((long int *) p, 0, 1)
+#endif
+
+#ifdef HAS_COMPARE_AND_SWAP_WITH_RELEASE_SEMANTICS
+
+static inline int
+compare_and_swap_with_release_semantics (long * ptr, long oldval,
+					 long newval, int * spinlock)
+{
+  return __compare_and_swap_with_release_semantics (ptr, oldval,
+						    newval);
+}
+
+#endif
+
 static inline int compare_and_swap(long * ptr, long oldval, long newval,
                                    int * spinlock)
 {
@@ -48,30 +85,90 @@ static inline int compare_and_swap(long * ptr, long oldval, long newval,
 
 #endif
 
+#ifndef HAS_COMPARE_AND_SWAP_WITH_RELEASE_SEMANTICS
+#define compare_and_swap_with_release_semantics compare_and_swap
+#define __compare_and_swap_with_release_semantics __compare_and_swap
+#endif
+
 /* Internal locks */
 
 extern void internal_function __pthread_lock(struct _pthread_fastlock * lock,
 					     pthread_descr self);
-extern void internal_function __pthread_unlock(struct _pthread_fastlock *lock);
+extern int __pthread_unlock(struct _pthread_fastlock *lock);
 
 static inline void __pthread_init_lock(struct _pthread_fastlock * lock)
 {
   lock->__status = 0;
-  lock->__spinlock = 0;
+  lock->__spinlock = __LT_SPINLOCK_INIT;
 }
 
 static inline int __pthread_trylock (struct _pthread_fastlock * lock)
 {
-  long oldstatus;
+#if defined TEST_FOR_COMPARE_AND_SWAP
+  if (!__pthread_has_cas)
+#endif
+#if !defined HAS_COMPARE_AND_SWAP || defined TEST_FOR_COMPARE_AND_SWAP
+  {
+    return (testandset(&lock->__spinlock) ? EBUSY : 0);
+  }
+#endif
 
+#if defined HAS_COMPARE_AND_SWAP
   do {
-    oldstatus = lock->__status;
-    if (oldstatus != 0) return EBUSY;
-  } while(! compare_and_swap(&lock->__status, 0, 1, &lock->__spinlock));
+    if (lock->__status != 0) return EBUSY;
+  } while(! __compare_and_swap(&lock->__status, 0, 1));
   return 0;
+#endif
+}
+
+/* Variation of internal lock used for pthread_mutex_t, supporting
+   timed-out waits.  Warning: do not mix these operations with the above ones
+   over the same lock object! */
+
+extern void __pthread_alt_lock(struct _pthread_fastlock * lock,
+			       pthread_descr self);
+
+extern int __pthread_alt_timedlock(struct _pthread_fastlock * lock,
+			       pthread_descr self, const struct timespec *abstime);
+
+extern void __pthread_alt_unlock(struct _pthread_fastlock *lock);
+
+static inline void __pthread_alt_init_lock(struct _pthread_fastlock * lock)
+{
+  lock->__status = 0;
+  lock->__spinlock = __LT_SPINLOCK_INIT;
 }
 
-#define LOCK_INITIALIZER {0, 0}
+static inline int __pthread_alt_trylock (struct _pthread_fastlock * lock)
+{
+#if defined TEST_FOR_COMPARE_AND_SWAP
+  if (!__pthread_has_cas)
+#endif
+#if !defined HAS_COMPARE_AND_SWAP || defined TEST_FOR_COMPARE_AND_SWAP
+  {
+    int res = EBUSY;
+
+    if (testandset(&lock->__spinlock) == 0)
+      {
+	if (lock->__status == 0)
+	  {
+	    lock->__status = 1;
+	    WRITE_MEMORY_BARRIER();
+	    res = 0;
+	  }
+	lock->__spinlock = __LT_SPINLOCK_INIT;
+      }
+    return res;
+  }
+#endif
+
+#if defined HAS_COMPARE_AND_SWAP
+  do {
+    if (lock->__status != 0) return EBUSY;
+  } while(! compare_and_swap(&lock->__status, 0, 1, &lock->__spinlock));
+  return 0;
+#endif
+}
 
 /* Operations on pthread_atomic, which is defined in internals.h */
 
@@ -98,5 +195,24 @@ static inline long atomic_decrement(struct pthread_atomic *pa)
     return oldval;
 }
 
-#define ATOMIC_INITIALIZER { 0, 0 }
 
+static inline void
+__pthread_set_own_extricate_if (pthread_descr self, pthread_extricate_if *peif)
+{
+  /* Only store a non-null peif if the thread has cancellation enabled.
+     Otherwise pthread_cancel will unconditionally call the extricate handler,
+     and restart the thread giving rise to forbidden spurious wakeups. */
+  if (peif == NULL
+      || THREAD_GETMEM(self, p_cancelstate) == PTHREAD_CANCEL_ENABLE)
+    {
+      /* If we are removing the extricate interface, we need to synchronize
+	 against pthread_cancel so that it does not continue with a pointer
+         to a deallocated pthread_extricate_if struct! The thread lock
+         is (ab)used for this synchronization purpose. */
+      if (peif == NULL)
+	__pthread_lock (THREAD_GETMEM(self, p_lock), self);
+      THREAD_SETMEM(self, p_extricate, peif);
+      if (peif == NULL)
+	__pthread_unlock (THREAD_GETMEM(self, p_lock));
+    }
+}