Add async I/O code to devpnc, but disabled for now: there is a delay

problem with remote terminal sessions:

1. netlink to remote Prime
2. a prirun
3. l (list directory)
4. displays a little, then a longish pause up to 30 seconds, then the rest

Does a similar thing with stat us.  Hitting Enter will cause it to
finish, while typing characters does not.  I suspect this is a problem
with Prime's networking code, but not sure.

Also, if async I/O is used, the QUIT. OK, message doesn't appear after
ctrl-p.  I think they are getting wiped out by Primenet's buffer
flushes.

All of this might be subtle timing problems because I changed the
default clock rate from 250/330/500/whatever times per sec to 20 times
per second in this rev 19 version of Primos.

devpnc.h

@@ -189,7 +189,7 @@
 
 #ifndef HOBBY
 
-/* PNC poll rate is 1/10th of a second */
+/* PNC poll rate in ms, mostly for connecting to new nodes */
 
 #define PNCPOLL 100
 
@@ -304,6 +304,15 @@ typedef struct {
 } t_dma;
 static t_dma rcv, xmit;
 
+static int sawsigio=0, olddevpoll;
+
+void pnchavedata(int s) {
+  if (sawsigio) return;
+  olddevpoll = devpoll[7];
+  devpoll[7] = 1;
+  sawsigio = 1;
+}
+
 /* return pointer to a hex-formatted uid */
 
 char * pnchexuid(char * uid) {
@@ -371,14 +380,22 @@ pncinitfd(int fd) {
     perror("unable to get ts flags for PNC");
     fatal(NULL);
   }
-  fdflags |= O_NONBLOCK;
+  optval = MAXPKTBYTES;
+  if (setsockopt(fd, SOL_SOCKET, SO_SNDLOWAT, &optval, sizeof(optval))) {
+    perror("setsockopt 2 failed for PNC");
+    fatal(NULL);
+  }
+  if (setsockopt(fd, SOL_SOCKET, SO_NOSIGPIPE, &optval, sizeof(optval))) {
+    perror("setsockopt 3 failed for PNC");
+    fatal(NULL);
+  }
+  fdflags |= O_NONBLOCK+O_ASYNC;
   if (fcntl(fd, F_SETFL, fdflags) == -1) {
     perror("unable to set fdflags for PNC");
     fatal(NULL);
   }
-  optval = MAXPKTBYTES;
+  if (fcntl(fd, F_SETOWN, getpid()) == -1) {
-  if (setsockopt(fd, SOL_SOCKET, SO_SNDLOWAT, &optval, sizeof(optval))) {
+    perror("unable to SETOWN for PNC");
-    perror("setsockopt failed for PNC");
     fatal(NULL);
   }
 }
@@ -872,6 +889,10 @@ int devpnc (int class, int func, int device) {
       perror("setsockopt failed for PNC listen");
       fatal(NULL);
     }
+    if (setsockopt(pncfd, SOL_SOCKET, SO_NOSIGPIPE, &optval, sizeof(optval))) {
+      perror("setsockopt 1 failed for PNC");
+      fatal(NULL);
+    }
     addr.sin_family = AF_INET;
     addr.sin_port = htons(nport);
     addr.sin_addr.s_addr = INADDR_ANY;
@@ -885,6 +906,12 @@ int devpnc (int class, int func, int device) {
     }
     TRACE(T_RIO, "PNC configured\n");
     devpoll[device] = PNCPOLL*gvp->instpermsec;
+#ifdef ASYNCIO
+    if (signal(SIGIO, pnchavedata) == SIG_ERR) {
+      perror("installing SIGIO handler");
+      fatal(NULL);
+    }
+#endif
     return 0;
 
   case 0:
@@ -1122,10 +1149,19 @@ int devpnc (int class, int func, int device) {
 
   case 4:
     TRACE(T_RIO, " POLL '%02o%02o\n", func, device);
-    devpoll[device] = PNCPOLL*gvp->instpermsec;
+
-    time(&timenow);
+    /* on SIGPIPE, reset to the previous poll time and just do reads;
-    pncaccept(timenow);   /* accept 1 new connection each poll */
+       otherwise, a regularly scheduled poll */
-    pncconnect(timenow);  /* try to connect to a disconnected node */
+
+    if (sawsigio) {
+      devpoll[device] = olddevpoll;
+      sawsigio = 0;
+    } else {
+      devpoll[device] = PNCPOLL*gvp->instpermsec;
+      time(&timenow);
+      pncaccept(timenow);   /* accept 1 new connection each poll */
+      pncconnect(timenow);  /* try to connect to a disconnected node */
+    }
 
 intrexit:
     if (rcv.state == PNCBSRDY)

em.c

@@ -6628,12 +6628,18 @@ d_bdx:  /* 0140734 */
       if (delayusec > 1000) {
 	if (gettimeofday(&tv0, NULL) != 0)
 	  fatal("em: gettimeofday 0 failed");
+
+	/* NOTE: on OSX, a signal (sigio for pnc) will interrupt usleep */
+
 	usleep(delayusec);
 	if (gettimeofday(&tv1, NULL) != 0)
 	  fatal("em: gettimeofday 1 failed");
 	actualmsec = (tv1.tv_sec-tv0.tv_sec-1)*1000 + (tv1.tv_usec+1000000-tv0.tv_usec)/1000;
-	// TRACEA(" BDX loop at %o/%o, remainder=%d, owner=%o, utempl=%d, wanted %d us, got %d ms\n", gvp->prevpc>>16, gvp->prevpc&0xffff, crs[X], crs[OWNERL], utempl, delayusec, actualusec);
+#if 0
-
+	if (actualmsec > delayusec*1.2/1000) {
+	  TRACEA(" BDX loop at %o/%o, remainder=%d, owner=%o, utempl=%d, wanted %d ms, got %d ms\n", gvp->prevpc>>16, gvp->prevpc&0xffff, crs[X], crs[OWNERL], utempl, delayusec/1000, actualmsec);
+	}
+#endif
 	/* do timer bookkeeping that would have occurred if we had 
 	   actually looped on BDX utempl times */