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listen1: add process limit option

--- a/sys/man/8/listen

+++ b/sys/man/8/listen

@@ -18,6 +18,8 @@

 [

 .B -tv

 ]

+.RB [ -p

+.IR maxprocs ]

 .I addr

 .I cmd

 [

--- a/sys/src/cmd/aux/listen1.c

+++ b/sys/src/cmd/aux/listen1.c

@@ -2,6 +2,7 @@

 #include <libc.h>

 #include <auth.h>

+int maxprocs;

 int verbose;

 int trusted;

@@ -8,7 +9,7 @@

 void

 usage(void)

 {

-	fprint(2, "usage: listen1 [-tv] address cmd args...\n");

+	fprint(2, "usage: listen1 [-tv] [-p maxprocs] address cmd args...\n");

 	exits("usage");

 }

@@ -51,8 +52,10 @@

 void

 main(int argc, char **argv)

 {

-	char data[60], dir[40], ndir[40];

+	char data[60], dir[40], ndir[40], wbuf[64];

 	int ctl, nctl, fd;

+	int wfd, nowait, procs;

+	Dir *d;

 	ARGBEGIN{

 	default:

@@ -63,6 +66,9 @@

 	case 'v':

 		verbose = 1;

 		break;

+	case 'p':

+		maxprocs = atoi(EARGF(usage()));

+		break;

 	}ARGEND

 	if(argc < 2)

@@ -85,12 +91,34 @@

 	if(ctl < 0)

 		sysfatal("announce %s: %r", argv[0]);

+	wfd = -1;

+	nowait = RFNOWAIT;

+	if(maxprocs > 0){

+		snprint(wbuf, sizeof(wbuf), "/proc/%d/wait", getpid());

+		if((wfd = open(wbuf, OREAD)) >= 0)

+			nowait = 0;

+	}

+	procs = 0;

 	for(;;){

+		if(nowait == 0 && (procs >= maxprocs || (procs % 8) == 0))

+			while(procs > 0){

+				if(procs < maxprocs){

+					d = dirfstat(wfd);

+					if(d == nil || d->length == 0){

+						free(d);

+						break;

+					}

+					free(d);

+				}

+				if(read(wfd, wbuf, sizeof(wbuf)) > 0)

+					procs--;

+			}

+

 		nctl = listen(dir, ndir);

 		if(nctl < 0)

 			sysfatal("listen %s: %r", argv[0]);

-		switch(rfork(RFFDG|RFPROC|RFNOWAIT|RFENVG|RFNAMEG|RFNOTEG)){

+		switch(rfork(RFFDG|RFPROC|RFMEM|RFENVG|RFNAMEG|RFNOTEG|nowait)){

 		case -1:

 			reject(nctl, ndir, "host overloaded");

 			close(nctl);

@@ -107,6 +135,8 @@

 			fprint(nctl, "keepalive");

 			close(ctl);

 			close(nctl);

+			if(wfd >= 0)

+				close(wfd);

 			putenv("net", ndir);

 			snprint(data, sizeof data, "%s/data", ndir);

 			bind(data, "/dev/cons", MREPL);

@@ -121,6 +151,7 @@

 			exits(nil);

 		default:

 			close(nctl);

+			procs++;

 			break;

 		}

 	}

-- 

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