Remove _THREAD_SAFE and make libc thread-safe by default by

adding (weak definitions to) stubs for some of the pthread
functions.  If the threads library is linked in, the real
pthread functions will pulled in.

Use the following convention for system calls wrapped by the
threads library:
	__sys_foo - actual system call
	_foo - weak definition to __sys_foo
	foo - weak definition to __sys_foo

Change all libc uses of system calls wrapped by the threads
library from foo to _foo.  In order to define the prototypes
for _foo(), we introduce namespace.h and un-namespace.h
(suggested by bde).  All files that need to reference these
system calls, should include namespace.h before any standard
includes, then include un-namespace.h after the standard
includes and before any local includes.  <db.h> is an exception
and shouldn't be included in between namespace.h and
un-namespace.h  namespace.h will define foo to _foo, and
un-namespace.h will undefine foo.

Try to eliminate some of the recursive calls to MT-safe
functions in libc/stdio in preparation for adding a mutex
to FILE.  We have recursive mutexes, but would like to avoid
using them if possible.

Remove uneeded includes of <errno.h> from a few files.

Add $FreeBSD$ to a few files in order to pass commitprep.

Approved by:	-arch

1 files changed, 40 insertions, 17 deletions

diff --git a/lib/libc/stdio/findfp.c b/lib/libc/stdio/findfp.c
index 3cc08a9..50edcb6 100644
--- a/lib/libc/stdio/findfp.c
+++ b/lib/libc/stdio/findfp.c
@@ -43,15 +43,15 @@ static const char rcsid[] =
 #endif /* LIBC_SCCS and not lint */
 
 #include <sys/param.h>
+#include <machine/atomic.h>
 #include <unistd.h>
 #include <stdio.h>
-#include <errno.h>
 #include <stdlib.h>
 #include <string.h>
 
-#include <libc_private.h>
 #include <spinlock.h>
 
+#include "libc_private.h"
 #include "local.h"
 #include "glue.h"
 
@@ -65,7 +65,7 @@ int	__sdidinit;
 
 				/* the usual - (stdin + stdout + stderr) */
 static FILE usual[FOPEN_MAX - 3];
-static struct glue uglue = { 0, FOPEN_MAX - 3, usual };
+static struct glue uglue = { NULL, FOPEN_MAX - 3, usual };
 
 FILE __sF[3] = {
 	std(__SRD, STDIN_FILENO),		/* stdin */
@@ -73,6 +73,7 @@ FILE __sF[3] = {
 	std(__SWR|__SNBF, STDERR_FILENO)	/* stderr */
 };
 struct glue __sglue = { &uglue, 3, __sF };
+static struct glue *lastglue = &uglue;
 
 static struct glue *	moreglue __P((int));
 
@@ -80,12 +81,18 @@ static spinlock_t thread_lock = _SPINLOCK_INITIALIZER;
 #define THREAD_LOCK()	if (__isthreaded) _SPINLOCK(&thread_lock)
 #define THREAD_UNLOCK()	if (__isthreaded) _SPINUNLOCK(&thread_lock)
 
+#if NOT_YET
+#define	SET_GLUE_PTR(ptr, val)	atomic_set_ptr(&(ptr), (uintptr_t)(val))
+#else
+#define	SET_GLUE_PTR(ptr, val)	ptr = val
+#endif
+
 static struct glue *
 moreglue(n)
-	register int n;
+	int n;
 {
-	register struct glue *g;
-	register FILE *p;
+	struct glue *g;
+	FILE *p;
 	static FILE empty;
 
 	g = (struct glue *)malloc(sizeof(*g) + ALIGNBYTES + n * sizeof(FILE));
@@ -106,22 +113,28 @@ moreglue(n)
 FILE *
 __sfp()
 {
-	register FILE *fp;
-	register int n;
-	register struct glue *g;
+	FILE	*fp;
+	int	n;
+	struct glue *g;
 
 	if (!__sdidinit)
 		__sinit();
+	/*
+	 * The list must be locked because a FILE may be updated.
+	 */
 	THREAD_LOCK();
-	for (g = &__sglue;; g = g->next) {
+	for (g = &__sglue; g != NULL; g = g->next) {
 		for (fp = g->iobs, n = g->niobs; --n >= 0; fp++)
 			if (fp->_flags == 0)
 				goto found;
-		if (g->next == NULL && (g->next = moreglue(NDYNAMIC)) == NULL)
-			break;
 	}
-	THREAD_UNLOCK();
-	return (NULL);
+	THREAD_UNLOCK();	/* don't hold lock while malloc()ing. */
+	if ((g == moreglue(NDYNAMIC)) == NULL)
+		return (NULL);
+	THREAD_LOCK();		/* reacquire the lock */
+	SET_GLUE_PTR(lastglue->next, g); /* atomically append glue to list */
+	lastglue = g;		/* not atomic; only accessed when locked */
+	fp = g->iobs;
 found:
 	fp->_flags = 1;		/* reserve this slot; caller sets real flags */
 	THREAD_UNLOCK();
@@ -137,6 +150,7 @@ found:
 	fp->_ub._size = 0;
 	fp->_lb._base = NULL;	/* no line buffer */
 	fp->_lb._size = 0;
+	/* fp->_lock = NULL; */
 	return (fp);
 }
 
@@ -150,14 +164,23 @@ __warn_references(f_prealloc,
 void
 f_prealloc()
 {
-	register struct glue *g;
+	struct glue *g;
 	int n;
 
 	n = getdtablesize() - FOPEN_MAX + 20;		/* 20 for slop. */
+	/*
+	 * It should be safe to walk the list without locking it;
+	 * new nodes are only added to the end and none are ever
+	 * removed.
+	 */
 	for (g = &__sglue; (n -= g->niobs) > 0 && g->next; g = g->next)
 		/* void */;
-	if (n > 0)
-		g->next = moreglue(n);
+	if ((n > 0) && ((g = moreglue(n)) != NULL)) {
+		THREAD_LOCK();
+		SET_GLUE_PTR(lastglue->next, g);
+		lastglue = g;
+		THREAD_UNLOCK();
+	}
 }
 
 /*