lwp: Simplify lwpSigWait() interface

lwpSigWait() was designed to resemble sigwait().  It doesn't anymore.
Drop the awkward argument, and use the return value instead.

Signed-off-by: Markus Armbruster <armbru@pond.sub.org>

include/lwp.h

@@ -64,7 +64,7 @@ void lwpYield(void);
 int lwpSleepFd(int fd, int flags, struct timeval *timeout);
 int lwpSleepUntil(time_t until);
 void lwpWakeup(struct lwpProc *);
-int lwpSigWait(int *sig);
+int lwpSigWait(void);
 void *lwpGetUD(struct lwpProc *);
 void lwpSetUD(struct lwpProc *, char *ud);
 int lwpSetPriority(int prio);

src/lib/empthread/lwp.c

@@ -117,13 +117,13 @@ empth_sleep(time_t until)
 int
 empth_wait_for_signal(void)
 {
-    int sig, err;
+    int sig;
     time_t now;
 
     ef_make_stale();
     for (;;) {
-	err = lwpSigWait(&sig);
+	sig = lwpSigWait();
-	if (CANT_HAPPEN(err)) {
+	if (CANT_HAPPEN(sig < 0)) {
 	    time(&now);
 	    lwpSleepUntil(now + 60);
 	    continue;

src/lib/lwp/sig.c

@@ -138,17 +138,17 @@ lwpGetSig(void)
 
 /*
  * Wait until one of the signals passed to lwpInitSigWait() arrives.
- * Assign its number to *@sig and return 0.
+ * Return its signal number.
- * If another thread is already waiting for signals, return EBUSY
+ * If another thread is already waiting for signals, return -1
  * without waiting.
  */
 int
-lwpSigWait(int *sig)
+lwpSigWait(void)
 {
     int res;
 
     if (LwpSigWaiter)
-	return EBUSY;
+	return -1;
     for (;;) {
 	res = lwpGetSig();
 	if (res > 0)
@@ -157,8 +157,7 @@ lwpSigWait(int *sig)
 	LwpSigWaiter = LwpCurrent;
 	lwpReschedule();
     }
-    *sig = res;
+    return res;
-    return 0;
 }
 
 /*