shithub: riscv

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--- a/sys/src/9/port/fault.c

+++ b/sys/src/9/port/fault.c

@@ -140,14 +140,20 @@

 		lkp = *pg;

 		lock(lkp);

-

+		if(lkp->ref <= 0)

+			panic("fault: lkp->ref %d <= 0", lkp->ref);

 		if(lkp->image == &swapimage)

 			ref = lkp->ref + swapcount(lkp->daddr);

 		else

 			ref = lkp->ref;

-		if(ref > 1) {

-			unlock(lkp);

+		if(ref == 1 && lkp->image){

+			/* save a copy of the original for the image cache */

+			duppage(lkp);

+			ref = lkp->ref;

+		}

+		unlock(lkp);

+		if(ref > 1){

 			new = newpage(0, &s, addr);

 			if(s == 0)

 				return -1;

@@ -154,13 +160,6 @@

 			*pg = new;

 			copypage(lkp, *pg);

 			putpage(lkp);

-		}

-		else {

-			/* save a copy of the original for the image cache */

-			if(lkp->image)

-				duppage(lkp);

-

-			unlock(lkp);

 		}

 		mmuphys = PPN((*pg)->pa) | PTEWRITE | PTEVALID;

 		(*pg)->modref = PG_MOD|PG_REF;

--- a/sys/src/9/port/page.c

+++ b/sys/src/9/port/page.c

@@ -275,7 +275,18 @@

 	retries = 0;

 retry:

+	/* don't dup shared page */

+	if(p->ref != 1){

+		print("duppage: p->ref %d != 1\n", p->ref);

+		return 0;

+	}

+	/* don't dup pages with no image */

+	if(p->image == nil || p->image->notext){

+		print("duppage: noimage\n");

+		return 0;

+	}

+

 	if(retries++ > dupretries){

 		print("duppage %d, up %p\n", retries, up);

 		dupretries += 100;

@@ -284,12 +295,7 @@

 		uncachepage(p);

 		return 1;

 	}

-		

-	/* don't dup pages with no image */

-	if(p->ref == 0 || p->image == nil || p->image->notext)

-		return 0;

-

 	/*

 	 *  normal lock ordering is to call

 	 *  lock(&palloc) before lock(p).

@@ -337,6 +343,8 @@

 * once they finally lock(np).

 */

 	lock(np);

+	if(np->ref != 0)	/* should never happen */

+		panic("duppage: np->ref %d != 0\n", np->ref);

 	unlock(&palloc);

 	/* Cache the new version */