git: 9front

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ref: e81d60c2bc87de6050d17060dad9c43a05fc06ac
parent: 18942824d915d353b3cf8a5c52b30e5164c25e56
author: cinap_lenrek <cinap_lenrek@gmx.de>
date: Sat Nov 2 13:54:42 EDT 2013 

rio: huge simplification of flush handling

xfidflush() now uses a simpler way to flush another xfid.

when we can send to Xfid.c channel, we know that the
xfid is completed. so all xfidflush() needs todo is to
do an alt sending to both Xfid.c and Xfid.flushc.

once the send to Xfid.c succeeds, we know the xfid is gone
and we can respond to the flush request.

theres no need to keep track of flush state anymore. so
Xfid.active and Xfid.flushing can be removed.

note, that it is ok to respond normally to a currently
flushed request.


--- a/sys/src/cmd/rio/dat.h
+++ b/sys/src/cmd/rio/dat.h
@@ -258,8 +258,6 @@
 		Fid		*f;
 		uchar	*buf;
 		Filsys	*fs;
-		QLock	active;
-		int		flushing;	/* another Xfid is trying to flush us */
 		int		flushtag;	/* our tag, so flush can find us */
 		Channel	*flushc;	/* channel(int) to notify us we're being flushed */
 };
--- a/sys/src/cmd/rio/fsys.c
+++ b/sys/src/cmd/rio/fsys.c
@@ -270,8 +270,6 @@
 	free(x->buf);
 	x->buf = nil;
 	x->flushtag = -1;
-	if(x->flushing)
-		recv(x->flushc, nil);	/* wakeup flushing xfid */
 	return x;
 }
 
--- a/sys/src/cmd/rio/xfid.c
+++ b/sys/src/cmd/rio/xfid.c
@@ -70,8 +70,6 @@
 				fprint(2, "%p incref %ld\n", x, x->ref);
 				error("incref");
 			}
-			if(x->flushing)
-				error("flushing in allocate");
 			if(x->flushtag != -1)
 				error("flushtag in allocate");
 			incref(x);
@@ -82,8 +80,6 @@
 				fprint(2, "%p decref %ld\n", x, x->ref);
 				error("decref");
 			}
-			if(x->flushing)
-				error("flushing in free");
 			if(x->flushtag != -1)
 				error("flushtag in free");
 			x->free = xfidfree;
@@ -114,8 +110,10 @@
 	threadsetname(buf);
 	for(;;){
 		f = recvp(x->c);
-		x->flushtag = x->tag;
-		(*f)(x);
+		if(f){
+			x->flushtag = x->tag;
+			(*f)(x);
+		}
 		if(decref(x) == 0)
 			sendp(cxfidfree, x);
 	}
@@ -146,28 +144,30 @@
 	sendul(x->fs->csyncflush, 0);
 
 	if(xf){
-		qlock(&xf->active);
-		if(xf->buf){	/* not responded yet? */
-			xf->flushing = TRUE;
-			qunlock(&xf->active);
-			sendul(xf->flushc, 0);
-			xf->flushing = FALSE;
-		}else{
-			qunlock(&xf->active);
-		}
-		if(decref(xf) == 0)
-			sendp(cxfidfree, xf);
-	}
+		enum { Done, Flush, End };
+		Alt alts[End+1];
+		void *f;
+		int z;
 
-	qlock(&x->active);
-	if(x->flushing){
-		qunlock(&x->active);
-		recv(x->flushc, nil);	/* wakeup flushing xfid */
+		z = 0;
+		f = nil;
+
+		alts[Done].c = xf->c;
+		alts[Done].v = &f;
+		alts[Done].op = CHANSND;
+		alts[Flush].c = xf->flushc;
+		alts[Flush].v = &z;
+		alts[Flush].op = CHANSND;
+		alts[End].op = CHANEND;
+
+		while(alt(alts) != Done)
+			;
+	}
+	if(nbrecv(x->flushc, nil)){
 		filsyscancel(x);
 		return;
 	}
 	filsysrespond(x->fs, x, &t, nil);
-	qunlock(&x->active);
 }
 
 void
@@ -439,16 +439,9 @@
 		case CWdata:
 			break;
 		case CWgone:
-			qlock(&x->active);
-			if(!x->flushing){
-				filsysrespond(x->fs, x, &fc, Edeleted);
-				qunlock(&x->active);
-				free(r);
-				return;
-			}
-			qunlock(&x->active);
-			recv(x->flushc, nil);	/* wake up flushing xfid */
-			/* no break */
+			filsysrespond(x->fs, x, &fc, Edeleted);
+			free(r);
+			return;
 		case CWflush:
 			free(r);
 			filsyscancel(x);
@@ -456,23 +449,11 @@
 		}
 
 		/* received data */
-		qlock(&x->active);
-		if(x->flushing){
-			qunlock(&x->active);
-			recv(x->flushc, nil);	/* wake up flushing xfid */
-			free(r);
-			pair.s = runemalloc(1);
-			pair.ns = 0;
-			send(cwm.cw, &pair);		/* wake up window with empty data */
-			filsyscancel(x);
-			return;
-		}
 		pair.s = r;
 		pair.ns = nr;
 		send(cwm.cw, &pair);
 		fc.count = x->count;
 		filsysrespond(x->fs, x, &fc, nil);
-		qunlock(&x->active);
 		return;
 
 	case Qconsctl:
@@ -678,15 +659,8 @@
 		case CRdata:
 			break;
 		case CRgone:
-			qlock(&x->active);
-			if(!x->flushing){
-				filsysrespond(x->fs, x, &fc, Edeleted);
-				qunlock(&x->active);
-				return;
-			}
-			qunlock(&x->active);
-			recv(x->flushc, nil);	/* wake up flushing xfid */
-			/* no break */
+			filsysrespond(x->fs, x, &fc, Edeleted);
+			return;
 		case CRflush:
 			filsyscancel(x);
 			return;
@@ -699,20 +673,10 @@
 		pair.s = t;
 		pair.ns = cnt;
 		send(c1, &pair);
-		qlock(&x->active);
-		if(x->flushing){
-			qunlock(&x->active);
-			recv(x->flushc, nil);	/* wake up flushing xfid */
-			recv(c2, nil);			/* wake up window and toss data */
-			free(t);
-			filsyscancel(x);
-			return;
-		}
 		recv(c2, &pair);
 		fc.data = pair.s;
 		fc.count = pair.ns;
 		filsysrespond(x->fs, x, &fc, nil);
-		qunlock(&x->active);
 		free(t);
 		break;
 
@@ -743,29 +707,12 @@
 		case MRdata:
 			break;
 		case MRgone:
-			qlock(&x->active);
-			if(!x->flushing){
-				filsysrespond(x->fs, x, &fc, Edeleted);
-				qunlock(&x->active);
-				return;
-			}
-			qunlock(&x->active);
-			recv(x->flushc, nil);	/* wake up flushing xfid */
-			/* no break */
+			filsysrespond(x->fs, x, &fc, Edeleted);
+			return;
 		case MRflush:
 			filsyscancel(x);
 			return;
 		}
-
-		/* received data */
-		qlock(&x->active);
-		if(x->flushing){
-			qunlock(&x->active);
-			recv(x->flushc, nil);		/* wake up flushing xfid */
-			recv(mrm.cm, nil);			/* wake up window and toss data */
-			filsyscancel(x);
-			return;
-		}
 		recv(mrm.cm, &ms);
 		c = 'm';
 		if(w->resized)
@@ -775,7 +722,6 @@
 		fc.data = buf;
 		fc.count = min(n, cnt);
 		filsysrespond(x->fs, x, &fc, nil);
-		qunlock(&x->active);
 		break;
 
 	case Qkbd:
@@ -794,15 +740,8 @@
 		case MRdata:
 			break;
 		case MRgone:
-			qlock(&x->active);
-			if(!x->flushing){
-				filsysrespond(x->fs, x, &fc, Edeleted);
-				qunlock(&x->active);
-				return;
-			}
-			qunlock(&x->active);
-			recv(x->flushc, nil);	/* wake up flushing xfid */
-			/* no break */
+			filsysrespond(x->fs, x, &fc, Edeleted);
+			return;
 		case MRflush:
 			filsyscancel(x);
 			return;
@@ -810,18 +749,9 @@
 
 		/* received data */
 		t = recvp(krm.ck);
-		qlock(&x->active);
-		if(x->flushing){
-			qunlock(&x->active);
-			free(t);		/* toss data */
-			recv(x->flushc, nil);		/* wake up flushing xfid */
-			filsyscancel(x);
-			return;
-		}
 		fc.data = t;
 		fc.count = strlen(t)+1;
 		filsysrespond(x->fs, x, &fc, nil);
-		qunlock(&x->active);
 		free(t);
 		break;
 
@@ -934,15 +864,8 @@
 		case WCRdata:
 			break;
 		case WCRgone:
-			qlock(&x->active);
-			if(!x->flushing){
-				filsysrespond(x->fs, x, &fc, Edeleted);
-				qunlock(&x->active);
-				return;
-			}
-			qunlock(&x->active);
-			recv(x->flushc, nil);	/* wake up flushing xfid */
-			/* no break */
+			filsysrespond(x->fs, x, &fc, Edeleted);
+			return;
 		case WCRflush:
 			filsyscancel(x);
 			return;
@@ -955,15 +878,6 @@
 		pair.s = t;
 		pair.ns = cnt+1;
 		send(c1, &pair);
-		qlock(&x->active);
-		if(x->flushing){
-			qunlock(&x->active);
-			recv(x->flushc, nil);	/* wake up flushing xfid */
-			recv(c2, nil);			/* wake up window and toss data */
-			free(t);
-			filsyscancel(x);
-			return;
-		}
 		recv(c2, &pair);
 		fc.data = pair.s;
 		if(pair.ns > cnt)
@@ -970,7 +884,6 @@
 			pair.ns = cnt;
 		fc.count = pair.ns;
 		filsysrespond(x->fs, x, &fc, nil);
-		qunlock(&x->active);
 		free(t);
 		break;
 
-- 
⑨