optimize POSIX TSD for fast pthread_getspecific

src/thread/pthread_getspecific.c

@@ -2,7 +2,6 @@
 
 void *pthread_getspecific(pthread_key_t k)
 {
-	struct pthread *self = pthread_self();
-	if (!self->tsd) return 0;
+	struct pthread *self = __pthread_self();
 	return self->tsd[k];
 }

src/thread/pthread_key_create.c

@@ -12,6 +12,7 @@ int pthread_key_create(pthread_key_t *k, void (*dtor)(void *))
 	int i = (uintptr_t)&k / 16 % PTHREAD_KEYS_MAX;
 	int j = i;
 
+	pthread_self();
 	libc.tsd_keys = keys;
 	if (!dtor) dtor = nodtor;
 	/* Cheap trick - &k cannot match any destructor pointer */

src/thread/pthread_self.c

@@ -2,6 +2,10 @@
 
 static struct pthread main_thread;
 
+/* pthread_key_create.c overrides this */
+static const size_t dummy = 0;
+weak_alias(dummy, __pthread_tsd_size);
+
 #undef errno
 static int *errno_location()
 {
@@ -10,6 +14,13 @@ static int *errno_location()
 
 static int init_main_thread()
 {
+	void *tsd = 0;
+	if (__pthread_tsd_size) {
+		tsd = mmap(0, __pthread_tsd_size, PROT_READ|PROT_WRITE,
+			MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
+		if (tsd == MAP_FAILED) return -1;
+	}
+	main_thread.tsd = tsd;
 	main_thread.self = &main_thread;
 	if (__set_thread_area(&main_thread) < 0)
 		return -1;

src/thread/pthread_setspecific.c

@@ -2,13 +2,7 @@
 
 int pthread_setspecific(pthread_key_t k, const void *x)
 {
-	struct pthread *self = pthread_self();
-	/* Handle the case of the main thread */
-	if (!self->tsd) {
-		if (!x) return 0;
-		if (!(self->tsd = calloc(sizeof(void *), PTHREAD_KEYS_MAX)))
-			return ENOMEM;
-	}
+	struct pthread *self = __pthread_self();
 	/* Avoid unnecessary COW */
 	if (self->tsd[k] != x) {
 		self->tsd[k] = (void *)x;