LinuxThreads library.

1998-03-11 00:42  Wolfram Gloger  <wmglo@dent.med.uni-muenchen.de>
	* linuxthreads/manager.c: Enable resetting of the thread
	scheduling policy to SCHED_OTHER when the parent thread
	has a different one.
1998-02-01 13:51  Ulrich Drepper  <drepper@cygnus.com>
	* sysdeps/unix/sysv/linux/bits/posix_opt.h: Define
	_POSIX_ASYNCHRONOUS_IO.
	* sysdeps/pthread/pthread.h: Define bits for Unix98 variants of
	mutexes.
	* mutex.c: Implement new mutex types.
	* internals.h: Include <signal.h>.
	* libpthread.map: Add __erno_location and __h_errno_location.
	* errno.c: Return pointer to variable actually in use.  This might
	not be the one in the thread structure.
	* internals.h (struct _pthread_descr_struct): Add new fields p_errnop
	and p_h_errnop.
	* manager.c (__pthread_manager): Set p_errnop and p_h_errnop member
	of manager thread structure.
	(pthread_handle_create): Set p_errnop and p_h_errnop members for new
	thread.
	* pthread.c: Adapt initializer for thread structures.
	(__pthread_initial_thread): Set p_errnop and p_h_errnop member.
	(__pthread_reset_main_thread): Reset p_errnop and p_h_errnop of
	current thread to global variables.
1998-01-31 17:27  Ulrich Drepper  <drepper@cygnus.com>
	* rwlock.c: New file.
	* Makefile (libpthread-routines): Add rwlock.
	* sysdeps/pthread/pthread.h: Define data structures and declare
	functions.
	* libpthread.map: Add new functions.
1997-12-18 13:50  Philip Blundell  <pb@nexus.co.uk>
	* sysdeps/arm/pt-machine.h: New file; add ARM support.
	* sysdeps/arm/Implies: likewise.
	* README: Document it.
1997-12-13  Andreas Schwab  <schwab@issan.informatik.uni-dortmund.de>
	* signals.c: Remove unneeded initializer for sigwaited, saving a
1997-04-11 01:18  Andreas Schwab  <schwab@issan.informatik.uni-dortmund.de>
	* semaphore.c (sem_init): Set sem_spinlock only if available.
1997-12-04 01:48  Ulrich Drepper  <drepper@cygnus.com>
	* mutex.c: Implement PTHREAD_MUTEX_CHECKERROR.
	* sysdeps/pthread/pthread.h: Define PTHREAD_MUTEX_CHECKERROR.
	* Makefile: Update from LinuxThreads 0.7.
	* internals.h. Likewise.
	* manager.c: Likewise.
	* mutex.c: Likewise.
	* pthread.c: Likewise.
	* signals.c: Likewise.
	* specific.c: Likewise.
	* Examples/ex3.c: Likewise.
1997-11-20 18:13  Ulrich Drepper  <drepper@cygnus.com>
	* pthread.c (__pthread_reset_main_thread): Close pipe only if still
	open.
1997-10-29 05:38  Ulrich Drepper  <drepper@cygnus.com>

	* wrapsyscall.c: Add socket functions which are also cancelation
	points.

1997-10-19 21:40  Wolfram Gloger  <wg@wolfram.dent.med.uni-muenchen.de>

	* specific.c (__libc_internal_tsd_set, __libc_internal_tsd_get):
	New functions for fast thread specific data within libc.

	* internals.h: Add new array p_libc_specific to struct
	_pthread_descr_struct.

	* sysdeps/pthread/bits/libc-lock.h: Declare new functions.

1997-10-13 05:39  Ulrich Drepper  <drepper@cygnus.com>

	* semaphore.h: Add __BEGIN_DECLS/__END_DECLS.
	Reported by Ralf Corsepius <corsepiu@faw.uni-ulm.de>.

1997-08-29 03:05  Ulrich Drepper  <drepper@cygnus.com>

	* internals.h (struct _pthread_descr_struct): Add definitions for
	two-level specific key handling.
	* manager.c (pthread_handle_create): Initialize specific memory array.
	* specific.c: Implement two-level key handling.
	* weaks.c: Don't provide dummy key handling.
	* sysdeps/pthread/bits/libc-lock.h: Typedef __libc_lock_t (no #define).
	Add definition of __libc_key_t.
	* sysdeps/unix/sysv/linux/bits/local_lim.h: Define PTHREAD_KEYS_MAX
	as 1024.
	Add definition of _POSIX_THREAD_DESTRUCTOR_ITERATIONS and
	PTHREAD_DESTRUCTOR_ITERATIONS.

	* manager.c (pthread_handle_create): Compare mmap result with
	MAP_FAILED.

	* ptfork.c: Rename to __pthread_atfork and make old name a weak alias.
	* sysdeps/pthread/bits/pthread.h: Add prototype for __pthread_atfork.

1997-08-22 19:04  Richard Henderson  <rth@cygnus.com>

	sysdeps/sparc -> sysdeps/sparc/sparc32
	sysdeps/sparc64 -> sysdeps/sparc/sparc64

	* internals.h: Change definition of THREAD_SELF to be an expression,
	not a statement that did a return.
	* sysdeps/alpha/pt-machine.h (THREAD_SELF): Update accordingly.
	* sysdeps/sparc/sparc32/pt-machine.h (THREAD_SELF, INIT_THREAD_SELF):
	Follow Solaris and use a "system reserved" register (%g6) to hold
	the thread descriptor.
	* sysdeps/sparc/sparc64/pt-machine.h: Likewise.

1997-08-03 00:09  Ulrich Drepper  <drepper@cygnus.com>

	* mutex.c: Correct pthread_once.  Patch by Xavier Leroy.
	* sysdeps/pthread/pthread.h: Add prototype for __pthread_once.
	* sysdeps/pthread/bits/pthread.h: Add macros for __libc_once.

	* semaphore.c: Include spinlock.h only when needed.

	* specific.c (__pthread_setsepcific, __pthread_getspecific): Reject
	keys for entries not in use.

	* weaks.c: Implement key handling functions for real.

1997-06-29  01:04  Richard Henderson  <richard@gnu.ai.mit.edu>

	Initial sparc64-linux support:
	* linuxthreads/sysdeps/sparc64/Implies: New file.
	* linuxthreads/sysdeps/sparc64/pt-machine.h: Likewise.

1997-06-29 00:48  Ulrich Drepper  <drepper@cygnus.com>

	* semaphore.c: Include spinlock.h at correct place.
	Patch by HJ Lu.

1997-06-13 10:06  Richard Henderson  <rth@tamu.edu>

	The Great Bit File Move:
	* sysdeps/alpha/semaphorebits.h: -> .../bits/semaphore.h.
	* sysdeps/powerpc/semaphorebits.h: Likewise.
	* sysdeps/pthread/cmpxchg/semaphorebits.h: Likewise.
	* sysdeps/pthread/no-cmpxchg/semaphorebits.h: Likewise.
	* sysdeps/pthread/libc-lock.h: -> bits/
	* sysdeps/pthread/stdio-lock.h: Likewise.
	* sysdeps/unix/sysv/linux/local_lim.h: Likewise.
	* sysdeps/unix/sysv/linux/posix_opt.h: Likewise.
	* semaphore.h: Likewise.
	* sysdeps/pthread/pthread.h: Likewise.

	* lockfile.c: <foo.h> -> <bits/foo.h>.
	* semaphore.h: Likewise.

	* Makefile: (headers): foo.h -> bits/foo.h.
	* sysdeps/pthread/Makefile: Likewise.

1997-04-11 01:18  Andreas Schwab  <schwab@issan.informatik.uni-dortmund.de>

	* semaphore.c (sem_init): Set sem_spinlock only if available.

	* sysdeps/m68k/pt-machine.h (testandset, __compare_and_swap): Fix
	asm constraints.

1997-04-09 03:00  Ulrich Drepper  <drepper@cygnus.com>

	Update from LinuxThreads 0.6.

	* attr.c (pthread_attr_getdetachstate): Use __sched_get_priority_max
	and __sched_get_priority_min instead of names without `__'.

	* manager.c: Rewrite large parts to implement opaque pthread_t.

	* cancel.c: Adapt for opaque pthread_t type.
	* condvar.c: Likewise.
	* errno.c: Likewise.
	* join.c: Likewise.
	* mutex.c: Likewise.
	* pthread.c: Likewise.
	* signals.c: Likewise.
	* specific.c: Likewise.
	* restart.h: Likewise.
	* queue.h: Likewise.
	* Examples/ex3.c: Likewise.
	* Examples/ex4.c: Likewise.
	* sysdeps/pthread/pthread.h: Likewise.

	* pthread.c: Accumulate time for all threads in thread manager.

	* semaphore.c: Implement fallback implementation for architectures
	sometimes missing compare-exchange operations.

	* cancel.c (pthread_cancel): Validate handle argument.
	* join.c (pthread_join): Likewise.
	(pthread_detach): Likewise.
	* signals.c (pthread_kill): Likewise.

	* spinlock.h (acquire): Use __sched_yield not sched_yield.

	* queue.h (enqueue): Enqueue thread according to priority.

	* internals.c (struct pthread_start_args): New struct for passing
	args to cloning function.
	(struct _pthread): Rename to _pthread_descr_struct and adapt for
	opaque pthread_t.

	* Examples/Makefile (clean): Pass -f option to rm.

	* sysdeps/i386/pt-machine.h: Add check for compare-exchange instruction
	and define TEST_FOR_COMPARE_AND_SWAP.
	* sysdeps/i386/i486/pt-machine.h: Removed.

	* sysdeps/unix/sysv/linux/local_lim.h (PTHREAD_THREADS_MAX): Increase
	to 1024.

1997-04-04 16:38  Ulrich Drepper  <drepper@cygnus.com>

	* restart.h (suspend): Clear p_signal before suspending.
	(suspend_with_cancellation): Likewise.
	Patch by Xavier Leroy <Xavier.Leroy@inria.fr>.

	* weaks.c: Make __pthread_key_create return 1.
	* sysdeps/pthread/libc-lock.h: Define __libc_key_create,
	__libc_getspecific, __libc_setspecific, and __libc_key_t.
	* sysdeps/pthread/stdio-lock.h: Don't care for implementation not
	using libio.

1997-03-19 15:13  Miguel de Icaza  <miguel@nuclecu.unam.mx>

	* sysdeps/sparc/pt-machine (RELEASE): Fix.

1997-03-01 07:55  Geoff Keating  <geoffk@ozemail.com.au>

	* sysdeps/powerpc/Implies: Added.
	* sysdeps/powerpc/pt-machine.h: Added.
	* sysdeps/powerpc/semaphorebits.h: Added.

1997-01-22 01:22  Ulrich Drepper  <drepper@cygnus.com>

	* linuxtheads/pthread.c (__pthread_initial_thread): Correct
	initializer.
	(__pthread_manager_thread): Likewise.
	Reported by Andreas Jaeger.

1997-01-18 22:15  Richard Henderson  <rth@tamu.edu>

	Since sigset_t no longer fits in a register, we can't pass in the
	thread's initial mask so easily.  Take this opportunity to simplify
	the clone implementation by only accepting a single void* argument.

	* linuxthreads/manager.c (__pthread_manager): Put thread vitals
	in the thread struct instead of as arguments through clone.
	(pthread_start_thread): Look for them there.
	* linuxthreads/internals.h (struct _pthread): Add p_initial_fn,
	p_initial_fn_arg, p_initial_mask.  Fix __pthread_manager proto.
	* linuxthreads/pthread.c (pthread_initialize_manager): Revise
	clone invocation.

6 files changed, 520 insertions, 0 deletions

diff --git a/linuxthreads/Examples/Makefile b/linuxthreads/Examples/Makefile
new file mode 100644
index 0000000..c68b367
--- /dev/null
+++ b/linuxthreads/Examples/Makefile
@@ -0,0 +1,15 @@
+CC=gcc
+CFLAGS=-g -O -Wall -I.. -D_REENTRANT
+LIBPTHREAD=../libpthread.a
+
+PROGS=ex1 ex2 ex3 ex4 ex5 proxy
+
+all: $(PROGS)
+
+.c:
+	$(CC) $(CFLAGS) -o $* $*.c $(LIBPTHREAD)
+
+$(PROGS):
+
+clean:
+	rm -f $(PROGS)
diff --git a/linuxthreads/Examples/ex1.c b/linuxthreads/Examples/ex1.c
new file mode 100644
index 0000000..c399fab
--- /dev/null
+++ b/linuxthreads/Examples/ex1.c
@@ -0,0 +1,36 @@
+/* Creates two threads, one printing 10000 "a"s, the other printing
+   10000 "b"s.
+   Illustrates: thread creation, thread joining. */
+
+#include <stddef.h>
+#include <stdio.h>
+#include <unistd.h>
+#include "pthread.h"
+
+void * process(void * arg)
+{
+  int i;
+  fprintf(stderr, "Starting process %s\n", (char *) arg);
+  for (i = 0; i < 10000; i++) {
+    write(1, (char *) arg, 1);
+  }
+  return NULL;
+}
+
+int main()
+{
+  int retcode;
+  pthread_t th_a, th_b;
+  void * retval;
+
+  retcode = pthread_create(&th_a, NULL, process, "a");
+  if (retcode != 0) fprintf(stderr, "create a failed %d\n", retcode);
+  retcode = pthread_create(&th_b, NULL, process, "b");
+  if (retcode != 0) fprintf(stderr, "create b failed %d\n", retcode);
+  retcode = pthread_join(th_a, &retval);
+  if (retcode != 0) fprintf(stderr, "join a failed %d\n", retcode);
+  retcode = pthread_join(th_b, &retval);
+  if (retcode != 0) fprintf(stderr, "join b failed %d\n", retcode);
+  return 0;
+}
+
diff --git a/linuxthreads/Examples/ex2.c b/linuxthreads/Examples/ex2.c
new file mode 100644
index 0000000..3f7f115
--- /dev/null
+++ b/linuxthreads/Examples/ex2.c
@@ -0,0 +1,116 @@
+/* The classic producer-consumer example.
+   Illustrates mutexes and conditions.
+   All integers between 0 and 9999 should be printed exactly twice,
+   once to the right of the arrow and once to the left. */
+
+#include <stdio.h>
+#include "pthread.h"
+
+#define BUFFER_SIZE 16
+
+/* Circular buffer of integers. */
+
+struct prodcons {
+  int buffer[BUFFER_SIZE];      /* the actual data */
+  pthread_mutex_t lock;         /* mutex ensuring exclusive access to buffer */
+  int readpos, writepos;        /* positions for reading and writing */
+  pthread_cond_t notempty;      /* signaled when buffer is not empty */
+  pthread_cond_t notfull;       /* signaled when buffer is not full */
+};
+
+/* Initialize a buffer */
+
+void init(struct prodcons * b)
+{
+  pthread_mutex_init(&b->lock, NULL);
+  pthread_cond_init(&b->notempty, NULL);
+  pthread_cond_init(&b->notfull, NULL);
+  b->readpos = 0;
+  b->writepos = 0;
+}
+
+/* Store an integer in the buffer */
+
+void put(struct prodcons * b, int data)
+{
+  pthread_mutex_lock(&b->lock);
+  /* Wait until buffer is not full */
+  while ((b->writepos + 1) % BUFFER_SIZE == b->readpos) {
+    pthread_cond_wait(&b->notfull, &b->lock);
+    /* pthread_cond_wait reacquired b->lock before returning */
+  }
+  /* Write the data and advance write pointer */
+  b->buffer[b->writepos] = data;
+  b->writepos++;
+  if (b->writepos >= BUFFER_SIZE) b->writepos = 0;
+  /* Signal that the buffer is now not empty */
+  pthread_cond_signal(&b->notempty);
+  pthread_mutex_unlock(&b->lock);
+}
+
+/* Read and remove an integer from the buffer */
+
+int get(struct prodcons * b)
+{
+  int data;
+  pthread_mutex_lock(&b->lock);
+  /* Wait until buffer is not empty */
+  while (b->writepos == b->readpos) {
+    pthread_cond_wait(&b->notempty, &b->lock);
+  }
+  /* Read the data and advance read pointer */
+  data = b->buffer[b->readpos];
+  b->readpos++;
+  if (b->readpos >= BUFFER_SIZE) b->readpos = 0;
+  /* Signal that the buffer is now not full */
+  pthread_cond_signal(&b->notfull);
+  pthread_mutex_unlock(&b->lock);
+  return data;
+}
+
+/* A test program: one thread inserts integers from 1 to 10000,
+   the other reads them and prints them. */
+
+#define OVER (-1)
+
+struct prodcons buffer;
+
+void * producer(void * data)
+{
+  int n;
+  for (n = 0; n < 10000; n++) {
+    printf("%d --->\n", n);
+    put(&buffer, n);
+  }
+  put(&buffer, OVER);
+  return NULL;
+}
+
+void * consumer(void * data)
+{
+  int d;
+  while (1) {
+    d = get(&buffer);
+    if (d == OVER) break;
+    printf("---> %d\n", d);
+  }
+  return NULL;
+}
+
+int main()
+{
+  pthread_t th_a, th_b;
+  void * retval;
+
+  init(&buffer);
+  /* Create the threads */
+  pthread_create(&th_a, NULL, producer, 0);
+  pthread_create(&th_b, NULL, consumer, 0);
+  /* Wait until producer and consumer finish. */
+  pthread_join(th_a, &retval);
+  pthread_join(th_b, &retval);
+  return 0;
+}
+  
+
+
diff --git a/linuxthreads/Examples/ex3.c b/linuxthreads/Examples/ex3.c
new file mode 100644
index 0000000..002bc90
--- /dev/null
+++ b/linuxthreads/Examples/ex3.c
@@ -0,0 +1,144 @@
+/* Multi-thread searching.
+   Illustrates: thread cancellation, cleanup handlers. */
+
+#include <stdio.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <pthread.h>
+
+/* Defines the number of searching threads */
+#define NUM_THREADS 5
+
+/* Function prototypes */
+void *search(void *);
+void print_it(void *);
+
+/* Global variables */
+pthread_t threads[NUM_THREADS];
+pthread_mutex_t lock;
+int tries;
+
+int main(argc, argv)
+     int argc;
+     char ** argv;
+{
+  int i;
+  int pid;
+
+  /* create a number to search for */
+  pid = getpid();
+  printf("Searching for the number = %d...\n", pid);
+
+  /* Initialize the mutex lock */
+  pthread_mutex_init(&lock, NULL); 
+
+  /* Create the searching threads */
+  for (i=0; i<NUM_THREADS; i++)
+    pthread_create(&threads[i], NULL, search, (void *)pid);
+
+  /* Wait for (join) all the searching threads */
+  for (i=0; i<NUM_THREADS; i++) 
+    pthread_join(threads[i], NULL);
+
+  printf("It took %d tries to find the number.\n", tries);
+
+  /* Exit the program */
+  return 0;
+}
+
+/* This is the cleanup function that is called 
+   when the threads are cancelled */
+
+void print_it(void *arg)
+{
+  int *try = (int *) arg;
+  pthread_t tid;
+
+  /* Get the calling thread's ID */
+  tid = pthread_self();
+
+  /* Print where the thread was in its search when it was cancelled */
+  printf("Thread %lx was canceled on its %d try.\n", tid, *try); 
+}
+
+/* This is the search routine that is executed in each thread */
+
+void *search(void *arg)
+{
+  int num = (int) arg;
+  int i, j, ntries;
+  pthread_t tid;
+
+  /* get the calling thread ID */
+  tid = pthread_self();
+
+  /* use the thread ID to set the seed for the random number generator */
+  /* Since srand and rand are not thread-safe, serialize with lock */
+  pthread_mutex_lock(&lock);
+  srand((int)tid);
+  i = rand() & 0xFFFFFF;
+  pthread_mutex_unlock(&lock);
+  ntries = 0;
+
+  /* Set the cancellation parameters --
+     - Enable thread cancellation 
+     - Defer the action of the cancellation */
+
+  pthread_setcancelstate(PTHREAD_CANCEL_ENABLE, NULL);
+  pthread_setcanceltype(PTHREAD_CANCEL_DEFERRED, NULL);
+
+  /* Push the cleanup routine (print_it) onto the thread
+     cleanup stack.  This routine will be called when the 
+     thread is cancelled.  Also note that the pthread_cleanup_push
+     call must have a matching pthread_cleanup_pop call.  The
+     push and pop calls MUST be at the same lexical level 
+     within the code */
+
+  /* Pass address of `ntries' since the current value of `ntries' is not 
+     the one we want to use in the cleanup function */
+
+  pthread_cleanup_push(print_it, (void *)&ntries);
+
+  /* Loop forever */
+  while (1) {
+    i = (i + 1) & 0xFFFFFF;
+    ntries++;
+
+    /* Does the random number match the target number? */
+    if (num == i) {
+      /* Try to lock the mutex lock --
+         if locked, check to see if the thread has been cancelled
+         if not locked then continue */
+      while (pthread_mutex_trylock(&lock) == EBUSY)
+        pthread_testcancel();
+
+      /* Set the global variable for the number of tries */
+      tries = ntries;
+      printf("Thread %lx found the number!\n", tid);
+
+      /* Cancel all the other threads */
+      for (j=0; j<NUM_THREADS; j++) 
+        if (threads[j] != tid) pthread_cancel(threads[j]);
+
+      /* Break out of the while loop */
+      break;
+    }
+
+    /* Every 100 tries check to see if the thread has been cancelled. */
+    if (ntries % 100 == 0) {
+      pthread_testcancel();
+    }
+  }
+
+  /* The only way we can get here is when the thread breaks out
+     of the while loop.  In this case the thread that makes it here
+     has found the number we are looking for and does not need to run
+     the thread cleanup function.  This is why the pthread_cleanup_pop
+     function is called with a 0 argument; this will pop the cleanup
+     function off the stack without executing it */
+
+  pthread_cleanup_pop(0);
+  return((void *)0);
+}
+
diff --git a/linuxthreads/Examples/ex4.c b/linuxthreads/Examples/ex4.c
new file mode 100644
index 0000000..83bc54c
--- /dev/null
+++ b/linuxthreads/Examples/ex4.c
@@ -0,0 +1,107 @@
+/* Making a library function that uses static variables thread-safe.
+   Illustrates: thread-specific data, pthread_once(). */
+
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <pthread.h>
+
+/* This is a typical example of a library function that uses
+   static variables to accumulate results between calls.
+   Here, it just returns the concatenation of all string arguments
+   that were given to it. */
+
+#if 0
+
+char * str_accumulate(char * s)
+{
+  static char accu[1024] = { 0 };
+  strcat(accu, s);
+  return accu;
+}
+
+#endif
+
+/* Of course, this cannot be used in a multi-threaded program
+   because all threads store "accu" at the same location.
+   So, we'll use thread-specific data to have a different "accu"
+   for each thread. */
+
+/* Key identifying the thread-specific data */
+static pthread_key_t str_key;
+/* "Once" variable ensuring that the key for str_alloc will be allocated
+   exactly once. */
+static pthread_once_t str_alloc_key_once = PTHREAD_ONCE_INIT;
+
+/* Forward functions */
+static void str_alloc_key(void);
+static void str_alloc_destroy_accu(void * accu);
+
+/* Thread-safe version of str_accumulate */
+
+char * str_accumulate(char * s)
+{
+  char * accu;
+
+  /* Make sure the key is allocated */
+  pthread_once(&str_alloc_key_once, str_alloc_key);
+  /* Get the thread-specific data associated with the key */
+  accu = (char *) pthread_getspecific(str_key);
+  /* It's initially NULL, meaning that we must allocate the buffer first. */
+  if (accu == NULL) {
+    accu = malloc(1024);
+    if (accu == NULL) return NULL;
+    accu[0] = 0;
+    /* Store the buffer pointer in the thread-specific data. */
+    pthread_setspecific(str_key, (void *) accu);
+    printf("Thread %lx: allocating buffer at %p\n", pthread_self(), accu);
+  }
+  /* Now we can use accu just as in the non thread-safe code. */
+  strcat(accu, s);
+  return accu;
+}
+
+/* Function to allocate the key for str_alloc thread-specific data. */
+
+static void str_alloc_key(void)
+{
+  pthread_key_create(&str_key, str_alloc_destroy_accu);
+  printf("Thread %lx: allocated key %d\n", pthread_self(), str_key);
+}
+
+/* Function to free the buffer when the thread exits. */
+/* Called only when the thread-specific data is not NULL. */
+
+static void str_alloc_destroy_accu(void * accu)
+{
+  printf("Thread %lx: freeing buffer at %p\n", pthread_self(), accu);
+  free(accu);
+}
+
+/* Test program */
+
+void * process(void * arg)
+{
+  char * res;
+  res = str_accumulate("Result of ");
+  res = str_accumulate((char *) arg);
+  res = str_accumulate(" thread");
+  printf("Thread %lx: \"%s\"\n", pthread_self(), res);
+  return NULL;
+}
+
+int main(int argc, char ** argv)
+{
+  char * res;
+  pthread_t th1, th2;
+
+  res = str_accumulate("Result of ");
+  pthread_create(&th1, NULL, process, "first");
+  pthread_create(&th2, NULL, process, "second");
+  res = str_accumulate("initial thread");
+  printf("Thread %lx: \"%s\"\n", pthread_self(), res);
+  pthread_join(th1, NULL);
+  pthread_join(th2, NULL);
+  pthread_exit(NULL);
+}
diff --git a/linuxthreads/Examples/ex5.c b/linuxthreads/Examples/ex5.c
new file mode 100644
index 0000000..366668e
--- /dev/null
+++ b/linuxthreads/Examples/ex5.c
@@ -0,0 +1,102 @@
+/* The classic producer-consumer example, implemented with semaphores.
+   All integers between 0 and 9999 should be printed exactly twice,
+   once to the right of the arrow and once to the left. */
+
+#include <stdio.h>
+#include "pthread.h"
+#include "semaphore.h"
+
+#define BUFFER_SIZE 16
+
+/* Circular buffer of integers. */
+
+struct prodcons {
+  int buffer[BUFFER_SIZE];      /* the actual data */
+  int readpos, writepos;        /* positions for reading and writing */
+  sem_t sem_read;               /* number of elements available for reading */
+  sem_t sem_write;              /* number of locations available for writing */
+};
+
+/* Initialize a buffer */
+
+void init(struct prodcons * b)
+{
+  sem_init(&b->sem_write, 0, BUFFER_SIZE - 1);
+  sem_init(&b->sem_read, 0, 0);
+  b->readpos = 0;
+  b->writepos = 0;
+}
+
+/* Store an integer in the buffer */
+
+void put(struct prodcons * b, int data)
+{
+  /* Wait until buffer is not full */
+  sem_wait(&b->sem_write);
+  /* Write the data and advance write pointer */
+  b->buffer[b->writepos] = data;
+  b->writepos++;
+  if (b->writepos >= BUFFER_SIZE) b->writepos = 0;
+  /* Signal that the buffer contains one more element for reading */
+  sem_post(&b->sem_read);
+}
+
+/* Read and remove an integer from the buffer */
+
+int get(struct prodcons * b)
+{
+  int data;
+  /* Wait until buffer is not empty */
+  sem_wait(&b->sem_read);
+  /* Read the data and advance read pointer */
+  data = b->buffer[b->readpos];
+  b->readpos++;
+  if (b->readpos >= BUFFER_SIZE) b->readpos = 0;
+  /* Signal that the buffer has now one more location for writing */
+  sem_post(&b->sem_write);
+  return data;
+}
+
+/* A test program: one thread inserts integers from 1 to 10000,
+   the other reads them and prints them. */
+
+#define OVER (-1)
+
+struct prodcons buffer;
+
+void * producer(void * data)
+{
+  int n;
+  for (n = 0; n < 10000; n++) {
+    printf("%d --->\n", n);
+    put(&buffer, n);
+  }
+  put(&buffer, OVER);
+  return NULL;
+}
+
+void * consumer(void * data)
+{
+  int d;
+  while (1) {
+    d = get(&buffer);
+    if (d == OVER) break;
+    printf("---> %d\n", d);
+  }
+  return NULL;
+}
+
+int main()
+{
+  pthread_t th_a, th_b;
+  void * retval;
+
+  init(&buffer);
+  /* Create the threads */
+  pthread_create(&th_a, NULL, producer, 0);
+  pthread_create(&th_b, NULL, consumer, 0);
+  /* Wait until producer and consumer finish. */
+  pthread_join(th_a, &retval);
+  pthread_join(th_b, &retval);
+  return 0;
+}