Add code to enforce the paralleism count (-j N) for the entire tree

of submakes spawned during processing.

We create a fifo and stuff one character into it for each job we are
allowed to run.  The name of the fifo is passed to child processes
in the MAKE_JOBS_FIFO environment variable.

A make which finds this variable on startup will open the fifo and
only spawn jobs when it managed to read a token from the fifo.
When the job completes a token is writen back to the fifo.

Slave make processes get one token for free: the one their parent
make got in order to run them.  This makes the make processes
themselves invisible in the process counts.

The net effect is that "make -j 12 -s buildworld" will start at
most 12 jobs at the same time, instead of as previously up to
65 jobs would get started.

1 files changed, 2 insertions, 2 deletions

diff --git a/usr.bin/make/make.c b/usr.bin/make/make.c
index 762b65a..4f85b68 100644
--- a/usr.bin/make/make.c
+++ b/usr.bin/make/make.c
@@ -637,7 +637,7 @@ MakeStartJobs (void)
 {
     GNode	*gn;
 
-    while (!Job_Full() && !Lst_IsEmpty (toBeMade)) {
+    while (!Lst_IsEmpty (toBeMade) && !Job_Full()) {
 	gn = (GNode *) Lst_DeQueue (toBeMade);
 	DEBUGF(MAKE, ("Examining %s...", gn->name));
 	/*
@@ -840,7 +840,7 @@ Make_Run (Lst targs)
      * keepgoing flag was given.
      */
     while (!Job_Empty ()) {
-	Job_CatchOutput ();
+	Job_CatchOutput (!Lst_IsEmpty (toBeMade));
 	Job_CatchChildren (!usePipes);
 	(void)MakeStartJobs();
     }