Compatibility versions of semaphore functions.
authordrepper <drepper>
Fri, 9 Jul 1999 21:03:20 +0000 (21:03 +0000)
committerdrepper <drepper>
Fri, 9 Jul 1999 21:03:20 +0000 (21:03 +0000)
linuxthreads/oldsemaphore.c [new file with mode: 0644]

diff --git a/linuxthreads/oldsemaphore.c b/linuxthreads/oldsemaphore.c
new file mode 100644 (file)
index 0000000..5a19a45
--- /dev/null
@@ -0,0 +1,215 @@
+/*
+ * This file contains the old semaphore code that we need to
+ * preserve for glibc-2.0 backwards compatibility. Port to glibc 2.1
+ * done by Cristian Gafton.
+ */
+
+/* Linuxthreads - a simple clone()-based implementation of Posix        */
+/* threads for Linux.                                                   */
+/* Copyright (C) 1996 Xavier Leroy (Xavier.Leroy@inria.fr)              */
+/*                                                                      */
+/* This program is free software; you can redistribute it and/or        */
+/* modify it under the terms of the GNU Library General Public License  */
+/* as published by the Free Software Foundation; either version 2       */
+/* of the License, or (at your option) any later version.               */
+/*                                                                      */
+/* This program is distributed in the hope that it will be useful,      */
+/* but WITHOUT ANY WARRANTY; without even the implied warranty of       */
+/* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the        */
+/* GNU Library General Public License for more details.                 */
+
+/* Semaphores a la POSIX 1003.1b */
+
+#include <errno.h>
+#include "pthread.h"
+#include "internals.h"
+#include "spinlock.h"
+#include "restart.h"
+#include "queue.h"
+
+typedef struct {
+    long int sem_status;
+    int sem_spinlock;
+} old_sem_t;
+
+/* Maximum value the semaphore can have.  */
+#define SEM_VALUE_MAX   ((int) ((~0u) >> 1))
+
+static inline int sem_compare_and_swap(old_sem_t *sem, long oldval, long newval)
+{
+    return __pthread_compare_and_swap(&sem->sem_status, oldval, newval, &sem->sem_spinlock);
+}
+
+/* The state of a semaphore is represented by a long int encoding
+   either the semaphore count if >= 0 and no thread is waiting on it,
+   or the head of the list of threads waiting for the semaphore.
+   To distinguish the two cases, we encode the semaphore count N
+   as 2N+1, so that it has the lowest bit set.
+
+   A sequence of sem_wait operations on a semaphore initialized to N
+   result in the following successive states:
+     2N+1, 2N-1, ..., 3, 1, &first_waiting_thread, &second_waiting_thread, ...
+*/
+
+static void sem_restart_list(pthread_descr waiting);
+
+int __old_sem_init(old_sem_t *sem, int pshared, unsigned int value)
+{
+    if (value > SEM_VALUE_MAX) {
+       errno = EINVAL;
+       return -1;
+    }
+    if (pshared) {
+       errno = ENOSYS;
+       return -1;
+    }
+  sem->sem_spinlock = 0;
+  sem->sem_status = ((long)value << 1) + 1;
+  return 0;
+}
+
+int __old_sem_wait(old_sem_t * sem)
+{
+    long oldstatus, newstatus;
+    volatile pthread_descr self = thread_self();
+    pthread_descr * th;
+
+    while (1) {
+       do {
+            oldstatus = sem->sem_status;
+            if ((oldstatus & 1) && (oldstatus != 1))
+               newstatus = oldstatus - 2;
+            else {
+               newstatus = (long) self;
+               self->p_nextwaiting = (pthread_descr) oldstatus;
+           }
+       }
+       while (! sem_compare_and_swap(sem, oldstatus, newstatus));
+       if (newstatus & 1)
+           /* We got the semaphore. */
+           return 0;
+       /* Wait for sem_post or cancellation */
+       suspend_with_cancellation(self);
+       /* This is a cancellation point */
+       if (self->p_canceled && self->p_cancelstate == PTHREAD_CANCEL_ENABLE) {
+           /* Remove ourselves from the waiting list if we're still on it */
+           /* First check if we're at the head of the list. */
+            do {
+               oldstatus = sem->sem_status;
+               if (oldstatus != (long) self) break;
+               newstatus = (long) self->p_nextwaiting;
+           }
+            while (! sem_compare_and_swap(sem, oldstatus, newstatus));
+            /* Now, check if we're somewhere in the list.
+              There's a race condition with sem_post here, but it does not matter:
+              the net result is that at the time pthread_exit is called,
+              self is no longer reachable from sem->sem_status. */
+            if (oldstatus != (long) self && (oldstatus & 1) == 0) {
+               for (th = &(((pthread_descr) oldstatus)->p_nextwaiting);
+                    *th != NULL && *th != (pthread_descr) 1;
+                    th = &((*th)->p_nextwaiting)) {
+                   if (*th == self) {
+                       *th = self->p_nextwaiting;
+                       break;
+                   }
+               }
+           }
+            pthread_exit(PTHREAD_CANCELED);
+       }
+    }
+}
+
+int __old_sem_trywait(old_sem_t * sem)
+{
+  long oldstatus, newstatus;
+
+  do {
+    oldstatus = sem->sem_status;
+    if ((oldstatus & 1) == 0 || (oldstatus == 1)) {
+      errno = EAGAIN;
+      return -1;
+    }
+    newstatus = oldstatus - 2;
+  }
+  while (! sem_compare_and_swap(sem, oldstatus, newstatus));
+  return 0;
+}
+
+int __old_sem_post(old_sem_t * sem)
+{
+  long oldstatus, newstatus;
+
+  do {
+    oldstatus = sem->sem_status;
+    if ((oldstatus & 1) == 0)
+      newstatus = 3;
+    else {
+      if (oldstatus >= SEM_VALUE_MAX) {
+        /* Overflow */
+        errno = ERANGE;
+        return -1;
+      }
+      newstatus = oldstatus + 2;
+    }
+  }
+  while (! sem_compare_and_swap(sem, oldstatus, newstatus));
+  if ((oldstatus & 1) == 0)
+    sem_restart_list((pthread_descr) oldstatus);
+  return 0;
+}
+
+int __old_sem_getvalue(old_sem_t * sem, int * sval)
+{
+  long status = sem->sem_status;
+  if (status & 1)
+    *sval = (int)((unsigned long) status >> 1);
+  else
+    *sval = 0;
+  return 0;
+}
+
+int __old_sem_destroy(old_sem_t * sem)
+{
+  if ((sem->sem_status & 1) == 0) {
+    errno = EBUSY;
+    return -1;
+  }
+  return 0;
+}
+
+/* Auxiliary function for restarting all threads on a waiting list,
+   in priority order. */
+
+static void sem_restart_list(pthread_descr waiting)
+{
+  pthread_descr th, towake, *p;
+
+  /* Sort list of waiting threads by decreasing priority (insertion sort) */
+  towake = NULL;
+  while (waiting != (pthread_descr) 1) {
+    th = waiting;
+    waiting = waiting->p_nextwaiting;
+    p = &towake;
+    while (*p != NULL && th->p_priority < (*p)->p_priority)
+      p = &((*p)->p_nextwaiting);
+    th->p_nextwaiting = *p;
+    *p = th;
+  }
+  /* Wake up threads in priority order */
+  while (towake != NULL) {
+    th = towake;
+    towake = towake->p_nextwaiting;
+    th->p_nextwaiting = NULL;
+    restart(th);
+  }
+}
+
+#if defined PIC && DO_VERSIONING
+symbol_version (__old_sem_init, sem_init, GLIBC_2.0);
+symbol_version (__old_sem_wait, sem_wait, GLIBC_2.0);
+symbol_version (__old_sem_trywait, sem_trywait, GLIBC_2.0);
+symbol_version (__old_sem_post, sem_post, GLIBC_2.0);
+symbol_version (__old_sem_getvalue, sem_getvalue, GLIBC_2.0);
+symbol_version (__old_sem_destroy, sem_destroy, GLIBC_2.0);
+#endif
+