Fix tar's handling of links.
 [rsc] --rw-rw-r-- M 23749 glenda sys 22453 Jan 31 07:50 sys/src/cmd/tar.c
	/n/sourcesdump/2006/0131/plan9/sys/src/cmd/tar.c:56,62 - 
	/n/sourcesdump/2006/0201/plan9/sys/src/cmd/tar.c:56,62
	  	LF_PLAIN2 =	'0',
	  	LF_LINK =	'1',
	  	LF_SYMLINK1 =	'2',
	- 	LF_SYMLINK2 =	's',
	+ 	LF_SYMLINK2 =	's',		/* 4BSD used this */
	  	LF_CHR =	'3',
	  	LF_BLK =	'4',
	  	LF_DIR =	'5',
	/n/sourcesdump/2006/0131/plan9/sys/src/cmd/tar.c:459,470 - 
	/n/sourcesdump/2006/0201/plan9/sys/src/cmd/tar.c:459,471
	  	return name(hp)[0] == '\0';
	  }
	  
	+ /* return the size from the header block, or zero for links, dirs, etc. */
	  Off
	  hdrsize(Hdr *hp)
	  {
	  	Off bytes = strtoull(hp->size, nil, 8);
	  
	- 	if(isdir(hp))
	+ 	if(isdir(hp) || islink(hp->linkflag))
	  		bytes = 0;
	  	return bytes;
	  }
	/n/sourcesdump/2006/0131/plan9/sys/src/cmd/tar.c:934,939 - 
	/n/sourcesdump/2006/0201/plan9/sys/src/cmd/tar.c:935,942
	  	} else
	  		print("%s\n", fname);
	  
	+ 	if (blksleft == 0)
	+ 		bytes = 0;
	  	for (; blksleft > 0; blksleft -= blksread) {
	  		hbp = getblkrd(ar, (fd >= 0? Alldata: Justnxthdr));
	  		if (hbp == nil)
	/n/sourcesdump/2006/0131/plan9/sys/src/cmd/tar.c:940,945 - 
	/n/sourcesdump/2006/0201/plan9/sys/src/cmd/tar.c:943,951
	  			sysfatal("unexpected EOF on archive extracting %s",
	  				fname);
	  		blksread = gothowmany(blksleft);
	+ 		if (blksread <= 0)
	+ 			fprint(2, "%s: got %ld blocks reading %s!\n",
	+ 				argv0, blksread, fname);
	  		wrbytes = Tblock*blksread;
	  		if(wrbytes > bytes)
	  			wrbytes = bytes;
	/n/sourcesdump/2006/0131/plan9/sys/src/cmd/tar.c:948,953 - 
	/n/sourcesdump/2006/0201/plan9/sys/src/cmd/tar.c:954,963
	  		putreadblks(ar, blksread);
	  		bytes -= wrbytes;
	  	}
	+ 	if (bytes > 0)
	+ 		fprint(2,
	+ 		    "%s: %lld bytes uncopied at eof; %s not fully extracted\n",
	+ 			argv0, bytes, fname);
	  	if (fd >= 0) {
	  		/*
	  		 * directories should be wstated after we're done

Remove debugging print.
 [jmk] --rw-rw-r-- M 23749 glenda sys 5589 Jan 31 11:12 sys/src/cmd/ip/ping.c
	/n/sourcesdump/2006/0131/plan9/sys/src/cmd/ip/ping.c:185,191 - 
	/n/sourcesdump/2006/0201/plan9/sys/src/cmd/ip/ping.c:185,190
	  		alarm(0);
	  		now = nsec();
	  		if(n <= 0){	/* read interrupted - time to go */
	- fprint(2, "clean\n");
	  			clean(0, now+MINUTE, nil);
	  			continue;
	  		}

Avoid holding locks too long in imagereclaim, 
and avoid rescheduling if it does happen.
 [rsc] --rw-rw-r-- M 23749 glenda sys 28702 Jan 31 18:16 sys/src/9/port/proc.c
	/n/sourcesdump/2006/0131/plan9/sys/src/9/port/proc.c:122,128 - 
	/n/sourcesdump/2006/0201/plan9/sys/src/9/port/proc.c:122,146
	  			getcallerpc(&p+2));
	  
	  	if(up){
	- 		if(up->nlocks.ref && up->state != Moribund && up->delaysched < 20){
	+ 		/*
	+ 		 * Delay the sched until the process gives up the locks
	+ 		 * it is holding.  This avoids dumb lock loops.
	+ 		 * Don't delay if the process is Moribund.
	+ 		 * It called sched to die.
	+ 		 * But do sched eventually.  This avoids a missing unlock
	+ 		 * from hanging the entire kernel. 
	+ 		 * But don't reschedule procs holding palloc or procalloc.
	+ 		 * Those are far too important to be holding while asleep.
	+ 		 *
	+ 		 * This test is not exact.  There can still be a few instructions
	+ 		 * in the middle of taslock when a process holds a lock
	+ 		 * but Lock.p has not yet been initialized.
	+ 		 */
	+ 		if(up->nlocks.ref)
	+ 		if(up->state != Moribund)
	+ 		if(up->delaysched < 20
	+ 		|| palloc.Lock.p == up
	+ 		|| procalloc.Lock.p == up){
	  			up->delaysched++;
	   			delayedscheds++;
	  			return;
 [rsc] --rw-rw-r-- M 23749 glenda sys 13939 Jan 31 18:16 sys/src/9/port/segment.c
	/n/sourcesdump/2006/0131/plan9/sys/src/9/port/segment.c:320,325 - 
	/n/sourcesdump/2006/0201/plan9/sys/src/9/port/segment.c:320,326
	  static void
	  imagereclaim(void)
	  {
	+ 	int n;
	  	Page *p;
	  	uvlong ticks;
	  
	/n/sourcesdump/2006/0131/plan9/sys/src/9/port/segment.c:330,339 - 
	/n/sourcesdump/2006/0201/plan9/sys/src/9/port/segment.c:331,348
	  
	  	lock(&palloc);
	  	ticks = fastticks(nil);
	- 	for(p = palloc.head; p; p = p->next) {
	- 		if(p->ref == 0 && p->image && canlock(p)) {
	- 			if(p->ref == 0)
	+ 	n = 0;
	+ 	/*
	+ 	 * All the pages with images backing them are at the
	+ 	 * end of the list (see putpage) so start there and work
	+ 	 * backward.
	+ 	 */
	+ 	for(p = palloc.tail; p && p->image && n<1000; p = p->prev) {
	+ 		if(p->ref == 0 && canlock(p)) {
	+ 			if(p->ref == 0) {
	+ 				n++;
	  				uncachepage(p);
	+ 			}
	  			unlock(p);
	  		}
	  	}