Merge in the pthread library. This is the linuxthreads library taken from

glibc 2.1.3 and ported to work with uClibc by Stefan Soucek and Erik Andersen
(me).  Stefan has hacked things up such that linuxthreads runs on MMU-less
systems (tested only on arm-nommu).  Erik cleaned things up and made it work
properly as a shared library.
 -Erik

1 files changed, 486 insertions, 0 deletions

diff --git a/libpthread/linuxthreads/rwlock.c b/libpthread/linuxthreads/rwlock.c
new file mode 100644
index 000000000..977fd88af
--- /dev/null
+++ b/libpthread/linuxthreads/rwlock.c
@@ -0,0 +1,486 @@
+/* Read-write lock implementation.
+   Copyright (C) 1998 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by Xavier Leroy <Xavier.Leroy@inria.fr>
+   and Ulrich Drepper <drepper@cygnus.com>, 1998.
+
+   The GNU C Library 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.
+
+   The GNU C Library 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.
+
+   You should have received a copy of the GNU Library General Public
+   License along with the GNU C Library; see the file COPYING.LIB.  If not,
+   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+   Boston, MA 02111-1307, USA.  */
+
+#include <errno.h>
+#include <pthread.h>
+#include <stdlib.h>
+#include "internals.h"
+#include "queue.h"
+#include "spinlock.h"
+#include "restart.h"
+
+/*
+ * Check whether the calling thread already owns one or more read locks on the
+ * specified lock. If so, return a pointer to the read lock info structure
+ * corresponding to that lock.
+ */
+
+static pthread_readlock_info *
+rwlock_is_in_list(pthread_descr self, pthread_rwlock_t *rwlock)
+{
+  pthread_readlock_info *info;
+
+  for (info = self->p_readlock_list; info != NULL; info = info->pr_next)
+    {
+      if (info->pr_lock == rwlock)
+	return info;
+    }
+
+  return NULL;
+}
+
+/*
+ * Add a new lock to the thread's list of locks for which it has a read lock.
+ * A new info node must be allocated for this, which is taken from the thread's
+ * free list, or by calling malloc. If malloc fails, a null pointer is
+ * returned. Otherwise the lock info structure is initialized and pushed
+ * onto the thread's list.
+ */
+
+static pthread_readlock_info *
+rwlock_add_to_list(pthread_descr self, pthread_rwlock_t *rwlock)
+{
+  pthread_readlock_info *info = self->p_readlock_free;
+
+  if (info != NULL) 
+    self->p_readlock_free = info->pr_next;
+  else
+    info = malloc(sizeof *info);
+
+  if (info == NULL)
+    return NULL;
+
+  info->pr_lock_count = 1;
+  info->pr_lock = rwlock;
+  info->pr_next = self->p_readlock_list;
+  self->p_readlock_list = info;
+
+  return info;
+}
+
+/*
+ * If the thread owns a read lock over the given pthread_rwlock_t,
+ * and this read lock is tracked in the thread's lock list,
+ * this function returns a pointer to the info node in that list.
+ * It also decrements the lock count within that node, and if
+ * it reaches zero, it removes the node from the list.
+ * If nothing is found, it returns a null pointer.
+ */
+
+static pthread_readlock_info *
+rwlock_remove_from_list(pthread_descr self, pthread_rwlock_t *rwlock)
+{
+  pthread_readlock_info **pinfo;
+
+  for (pinfo = &self->p_readlock_list; *pinfo != NULL; pinfo = &(*pinfo)->pr_next)
+    {
+      if ((*pinfo)->pr_lock == rwlock)
+	{
+	  pthread_readlock_info *info = *pinfo;
+	  if (--info->pr_lock_count == 0)
+	    *pinfo = info->pr_next;
+	  return info;
+	}
+    }
+  
+  return NULL;
+}
+
+/*
+ * This function checks whether the conditions are right to place a read lock.
+ * It returns 1 if so, otherwise zero. The rwlock's internal lock must be
+ * locked upon entry.
+ */
+
+static int
+rwlock_can_rdlock(pthread_rwlock_t *rwlock, int have_lock_already)
+{
+  /* Can't readlock; it is write locked. */
+  if (rwlock->__rw_writer != NULL)
+    return 0;
+
+  /* Lock prefers readers; get it. */
+  if (rwlock->__rw_kind == PTHREAD_RWLOCK_PREFER_READER_NP)
+    return 1;
+
+  /* Lock prefers writers, but none are waiting. */
+  if (queue_is_empty(&rwlock->__rw_write_waiting))
+    return 1;
+
+  /* Writers are waiting, but this thread already has a read lock */
+  if (have_lock_already)
+    return 1;
+
+  /* Writers are waiting, and this is a new lock */
+  return 0;
+}
+
+/*
+ * This function helps support brain-damaged recursive read locking
+ * semantics required by Unix 98, while maintaining write priority.
+ * This basically determines whether this thread already holds a read lock
+ * already. It returns 1 if so, otherwise it returns 0.  
+ *
+ * If the thread has any ``untracked read locks'' then it just assumes
+ * that this lock is among them, just to be safe, and returns 1.
+ *
+ * Also, if it finds the thread's lock in the list, it sets the pointer
+ * referenced by pexisting to refer to the list entry.
+ *
+ * If the thread has no untracked locks, and the lock is not found
+ * in its list, then it is added to the list. If this fails,
+ * then *pout_of_mem is set to 1.
+ */
+
+static int
+rwlock_have_already(pthread_descr *pself, pthread_rwlock_t *rwlock,
+    pthread_readlock_info **pexisting, int *pout_of_mem)
+{
+  pthread_readlock_info *existing = NULL;
+  int out_of_mem = 0, have_lock_already = 0;
+  pthread_descr self = *pself;
+
+  if (rwlock->__rw_kind == PTHREAD_RWLOCK_PREFER_WRITER_NP)
+    {
+      if (!self)
+	self = thread_self();
+
+      existing = rwlock_is_in_list(self, rwlock);
+
+      if (existing != NULL || self->p_untracked_readlock_count > 0)
+	have_lock_already = 1;
+      else
+	{
+	  existing = rwlock_add_to_list(self, rwlock);
+	  if (existing == NULL)
+	    out_of_mem = 1;
+	}
+    }
+
+  *pout_of_mem = out_of_mem;
+  *pexisting = existing;
+  *pself = self;
+
+  return have_lock_already;
+}
+
+int
+pthread_rwlock_init (pthread_rwlock_t *rwlock,
+		     const pthread_rwlockattr_t *attr)
+{
+  __pthread_init_lock(&rwlock->__rw_lock);
+  rwlock->__rw_readers = 0;
+  rwlock->__rw_writer = NULL;
+  rwlock->__rw_read_waiting = NULL;
+  rwlock->__rw_write_waiting = NULL;
+
+  if (attr == NULL)
+    {
+      rwlock->__rw_kind = PTHREAD_RWLOCK_DEFAULT_NP;
+      rwlock->__rw_pshared = PTHREAD_PROCESS_PRIVATE;
+    }
+  else
+    {
+      rwlock->__rw_kind = attr->__lockkind;
+      rwlock->__rw_pshared = attr->__pshared;
+    }
+
+  return 0;
+}
+
+
+int
+pthread_rwlock_destroy (pthread_rwlock_t *rwlock)
+{
+  int readers;
+  _pthread_descr writer;
+
+  __pthread_lock (&rwlock->__rw_lock, NULL);
+  readers = rwlock->__rw_readers;
+  writer = rwlock->__rw_writer;
+  __pthread_unlock (&rwlock->__rw_lock);
+
+  if (readers > 0 || writer != NULL)
+    return EBUSY;
+
+  return 0;
+}
+
+int
+pthread_rwlock_rdlock (pthread_rwlock_t *rwlock)
+{
+  pthread_descr self = NULL;
+  pthread_readlock_info *existing;
+  int out_of_mem, have_lock_already;
+
+  have_lock_already = rwlock_have_already(&self, rwlock,
+      &existing, &out_of_mem);
+
+  for (;;)
+    {
+      if (self == NULL)
+	self = thread_self ();
+
+      __pthread_lock (&rwlock->__rw_lock, self);
+
+      if (rwlock_can_rdlock(rwlock, have_lock_already))
+	break;
+
+      enqueue (&rwlock->__rw_read_waiting, self);
+      __pthread_unlock (&rwlock->__rw_lock);
+      suspend (self); /* This is not a cancellation point */
+    }
+
+  ++rwlock->__rw_readers;
+  __pthread_unlock (&rwlock->__rw_lock);
+
+  if (have_lock_already || out_of_mem)
+    {
+      if (existing != NULL)
+	existing->pr_lock_count++;
+      else
+	self->p_untracked_readlock_count++;
+    }
+  
+  return 0;
+}
+
+int
+pthread_rwlock_tryrdlock (pthread_rwlock_t *rwlock)
+{
+  pthread_descr self = thread_self();
+  pthread_readlock_info *existing;
+  int out_of_mem, have_lock_already;
+  int retval = EBUSY;
+
+  have_lock_already = rwlock_have_already(&self, rwlock,
+      &existing, &out_of_mem);
+
+  __pthread_lock (&rwlock->__rw_lock, self);
+
+  /* 0 is passed to here instead of have_lock_already.
+     This is to meet Single Unix Spec requirements: 
+     if writers are waiting, pthread_rwlock_tryrdlock
+     does not acquire a read lock, even if the caller has
+     one or more read locks already. */
+
+  if (rwlock_can_rdlock(rwlock, 0))
+    {
+      ++rwlock->__rw_readers;
+      retval = 0;
+    }
+
+  __pthread_unlock (&rwlock->__rw_lock);
+
+  if (retval == 0)
+    {
+      if (have_lock_already || out_of_mem)
+	{
+	  if (existing != NULL)
+	    existing->pr_lock_count++;
+	  else
+	    self->p_untracked_readlock_count++;
+	}
+    }
+  
+  return retval;
+}
+
+
+int
+pthread_rwlock_wrlock (pthread_rwlock_t *rwlock)
+{
+  pthread_descr self = thread_self ();
+
+  while(1)
+    {
+      __pthread_lock (&rwlock->__rw_lock, self);
+      if (rwlock->__rw_readers == 0 && rwlock->__rw_writer == NULL)
+	{
+	  rwlock->__rw_writer = self;
+	  __pthread_unlock (&rwlock->__rw_lock);
+	  return 0;
+	}
+
+      /* Suspend ourselves, then try again */
+      enqueue (&rwlock->__rw_write_waiting, self);
+      __pthread_unlock (&rwlock->__rw_lock);
+      suspend (self); /* This is not a cancellation point */
+    }
+}
+
+
+int
+pthread_rwlock_trywrlock (pthread_rwlock_t *rwlock)
+{
+  int result = EBUSY;
+
+  __pthread_lock (&rwlock->__rw_lock, NULL);
+  if (rwlock->__rw_readers == 0 && rwlock->__rw_writer == NULL)
+    {
+      rwlock->__rw_writer = thread_self ();
+      result = 0;
+    }
+  __pthread_unlock (&rwlock->__rw_lock);
+
+  return result;
+}
+
+
+int
+pthread_rwlock_unlock (pthread_rwlock_t *rwlock)
+{
+  pthread_descr torestart;
+  pthread_descr th;
+
+  __pthread_lock (&rwlock->__rw_lock, NULL);
+  if (rwlock->__rw_writer != NULL)
+    {
+      /* Unlocking a write lock.  */
+      if (rwlock->__rw_writer != thread_self ())
+	{
+	  __pthread_unlock (&rwlock->__rw_lock);
+	  return EPERM;
+	}
+      rwlock->__rw_writer = NULL;
+
+      if (rwlock->__rw_kind == PTHREAD_RWLOCK_PREFER_READER_NP
+	  || (th = dequeue (&rwlock->__rw_write_waiting)) == NULL)
+	{
+	  /* Restart all waiting readers.  */
+	  torestart = rwlock->__rw_read_waiting;
+	  rwlock->__rw_read_waiting = NULL;
+	  __pthread_unlock (&rwlock->__rw_lock);
+	  while ((th = dequeue (&torestart)) != NULL)
+	    restart (th);
+	}
+      else
+	{
+	  /* Restart one waiting writer.  */
+	  __pthread_unlock (&rwlock->__rw_lock);
+	  restart (th);
+	}
+    }
+  else
+    {
+      /* Unlocking a read lock.  */
+      if (rwlock->__rw_readers == 0)
+	{
+	  __pthread_unlock (&rwlock->__rw_lock);
+	  return EPERM;
+	}
+
+      --rwlock->__rw_readers;
+      if (rwlock->__rw_readers == 0)
+	/* Restart one waiting writer, if any.  */
+	th = dequeue (&rwlock->__rw_write_waiting);
+      else
+	th = NULL;
+
+      __pthread_unlock (&rwlock->__rw_lock);
+      if (th != NULL)
+	restart (th);
+
+      /* Recursive lock fixup */
+
+      if (rwlock->__rw_kind == PTHREAD_RWLOCK_PREFER_WRITER_NP)
+	{
+	  pthread_descr self = thread_self();
+	  pthread_readlock_info *victim = rwlock_remove_from_list(self, rwlock);
+
+	  if (victim != NULL)
+	    {
+	      if (victim->pr_lock_count == 0)
+		{
+		  victim->pr_next = self->p_readlock_free;
+		  self->p_readlock_free = victim;
+		}
+	    }
+	  else
+	    {
+	      if (self->p_untracked_readlock_count > 0)
+		self->p_untracked_readlock_count--;
+	    }
+	}
+    }
+
+  return 0;
+}
+
+
+
+int
+pthread_rwlockattr_init (pthread_rwlockattr_t *attr)
+{
+  attr->__lockkind = 0;
+  attr->__pshared = 0;
+
+  return 0;
+}
+
+
+int
+pthread_rwlockattr_destroy (pthread_rwlockattr_t *attr)
+{
+  return 0;
+}
+
+
+int
+pthread_rwlockattr_getpshared (const pthread_rwlockattr_t *attr, int *pshared)
+{
+  *pshared = attr->__pshared;
+  return 0;
+}
+
+
+int
+pthread_rwlockattr_setpshared (pthread_rwlockattr_t *attr, int pshared)
+{
+  if (pshared != PTHREAD_PROCESS_PRIVATE && pshared != PTHREAD_PROCESS_SHARED)
+    return EINVAL;
+
+  attr->__pshared = pshared;
+
+  return 0;
+}
+
+
+int
+pthread_rwlockattr_getkind_np (const pthread_rwlockattr_t *attr, int *pref)
+{
+  *pref = attr->__lockkind;
+  return 0;
+}
+
+
+int
+pthread_rwlockattr_setkind_np (pthread_rwlockattr_t *attr, int pref)
+{
+  if (pref != PTHREAD_RWLOCK_PREFER_READER_NP
+      && pref != PTHREAD_RWLOCK_PREFER_WRITER_NP
+      && pref != PTHREAD_RWLOCK_DEFAULT_NP)
+    return EINVAL;
+
+  attr->__lockkind = pref;
+
+  return 0;
+}