Add a magic field to the pthread structure to help recognize valid

threads from invalid ones. The pthread structure is opaque to the user
so this change does not cause any incompatibilities.

Hopefully this change will help code that was written for draft 4
fail gracefully if the programmer ignores the compiler warning about
the change in the level of indirection for the argument passed to
pthread_detach(). I got burnt, so I fixed then (expletive deleted)
thing.

These functions comply with the revised standard. That should shut
Terry up!

4 files changed, 25 insertions, 2 deletions

diff --git a/lib/libpthread/thread/thr_create.c b/lib/libpthread/thread/thr_create.c
index da00e4d..412f558 100644
--- a/lib/libpthread/thread/thr_create.c
+++ b/lib/libpthread/thread/thr_create.c
@@ -60,6 +60,12 @@ _thread_create(pthread_t * thread, const pthread_attr_t * attr,
 		/* Insufficient memory to create a thread: */
 		ret = EAGAIN;
 	} else {
+		/*
+		 * Write a magic value to the thread structure to help
+		 * identify valid ones:
+		 */
+		new_thread->magic = PTHREAD_MAGIC;
+
 		/* Check if default thread attributes are required: */
 		if (attr == NULL || *attr == NULL) {
 			/* Use the default thread attributes: */
diff --git a/lib/libpthread/thread/thr_detach.c b/lib/libpthread/thread/thr_detach.c
index a9f2469..57c073a 100644
--- a/lib/libpthread/thread/thr_detach.c
+++ b/lib/libpthread/thread/thr_detach.c
@@ -46,7 +46,7 @@ pthread_detach(pthread_t pthread)
 	_thread_kern_sig_block(&status);
 
 	/* Check for invalid calling parameters: */
-	if (pthread == NULL) {
+	if (pthread == NULL || pthread->magic != PTHREAD_MAGIC) {
 		/* Return an invalid argument error: */
 		rval = EINVAL;
 	}
diff --git a/lib/libpthread/thread/thr_join.c b/lib/libpthread/thread/thr_join.c
index 63d0d58..9e86a01 100644
--- a/lib/libpthread/thread/thr_join.c
+++ b/lib/libpthread/thread/thr_join.c
@@ -42,6 +42,16 @@ pthread_join(pthread_t pthread, void **thread_return)
 	int             status;
 	pthread_t	pthread1;
 
+	/* Check if the caller has specified an invalid thread: */
+	if (pthread == NULL || pthread->magic != PTHREAD_MAGIC)
+		/* Invalid thread: */
+		return(EINVAL);
+
+	/* Check if the caller has specified itself: */
+	if (pthread == _thread_run)
+		/* Avoid a deadlock condition: */
+		return(EDEADLK);
+
 	/* Block signals: */
 	_thread_kern_sig_block(&status);
 
diff --git a/lib/libpthread/thread/thr_private.h b/lib/libpthread/thread/thr_private.h
index 7d5bf89..e4b377a 100644
--- a/lib/libpthread/thread/thr_private.h
+++ b/lib/libpthread/thread/thr_private.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1995 John Birrell <jb@cimlogic.com.au>.
+ * Copyright (c) 1995-1998 John Birrell <jb@cimlogic.com.au>.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -278,6 +278,13 @@ union pthread_wait_data {
  */
 struct pthread {
 	/*
+	 * Magic value to help recognize a valid thread structure
+	 * from an invalid one:
+	 */
+#define	PTHREAD_MAGIC		((u_int32_t) 0xd09ba115)
+	u_int32_t		magic;
+
+	/*
 	 * Pointer to the next thread in the thread linked list.
 	 */
 	struct pthread	*nxt;