From fb6042c5cd8a411cfcfcf6c1a1d466eb42a4ff33 Mon Sep 17 00:00:00 2001
From: John Denker <jsd@av8n.com>
Date: Sat, 14 Jul 2012 23:13:38 -0700
Subject: working toward a process-group signalling system

---
 tools/hi-q.c | 37 +++++++++++++++++++++++++------------
 1 file changed, 25 insertions(+), 12 deletions(-)

(limited to 'tools/hi-q.c')

diff --git a/tools/hi-q.c b/tools/hi-q.c
index a065ad0..14ca5ec 100644
--- a/tools/hi-q.c
+++ b/tools/hi-q.c
@@ -197,17 +197,16 @@ int main(int argc, char** argv, char const * const * env) {
     }
     if (job.size()) filter.push_back(job);
   }
-  if (verbose) for (vector<VS>::const_iterator job = filter.begin();
-        job != filter.end(); job++) {
-    cerr << "Filter: ";
-    for (VS::const_iterator token = job->begin();
-        token != job->end(); token++){
+  unsigned int nkids = filter.size();
+  if (verbose) for (unsigned int ii = 0; ii < nkids; ii++) {
+    cerr << "hi-q filter[" << ii << "] :; ";
+    for (VS::const_iterator token = filter[ii].begin();
+        token != filter[ii].end(); token++){
       cerr << *token << " ";
     }
     cerr << endl;
   }
 
-  int nkids = filter.size();
   vector<pid_t> kidpid(nkids);  // indexed by kid number
 
 // At this point, there are some loop invariants;
@@ -218,7 +217,7 @@ int main(int argc, char** argv, char const * const * env) {
 //     doesn't choose it.  That allows N-1 of the kids
 //     to close it and dup() something useful onto it.
 
-  for (int ii=0; ii < nkids; ii++){  /* loop over all kids */
+  for (unsigned int ii=0; ii < nkids; ii++){  /* loop over all kids */
     int datapipe[2];
     int kid_end;
 
@@ -256,6 +255,16 @@ int main(int argc, char** argv, char const * const * env) {
     kidpid[ii] = fork();
     if (!kidpid[ii]) {  /*** child code ***/
 
+      pid_t kidgroup(0);    // process group for all kids is
+                            // equal to pid of kid#0
+      if (ii) kidgroup = kidpid[0];
+      if (setpgid(0, kidgroup) != 0) {
+        cerr << "setpgid failed! " << errno << " ... ";
+        perror(0);
+      }
+      cerr << "kid [" << ii << "] starts: " << getpid() 
+        << "  kidpid[0] " << kidpid[0]
+        << endl;
 // Now that we are through creating pipes, we don't
 // need to continue blocking fd1:
       close(1);
@@ -295,10 +304,14 @@ int main(int argc, char** argv, char const * const * env) {
       panic(ex_syserr);
     }
     close(kid_end);
-#ifdef more_testing
-    fprintf(stderr, "forked kid #%d (%d) piping %d\n",
-                ii, kidpid[ii], kid_end);
-//    sleep(1); /* let kid run a while */
+// it is important to let kid#0 run a while;
+// otherwise it won't fully exist when the other kids start,
+// and depending race conditions, the setpgid could fail
+    if (1) usleep(0);
+#if 1
+    cerr << "forked kid #" << ii 
+            << " (" << kidpid[ii] << ") "
+            << endl;
 #endif
   }
 
@@ -307,7 +320,7 @@ int main(int argc, char** argv, char const * const * env) {
   close(0);             // the reading end of stdin was
                         // delegated to the first child
 
-  for (int ii=0; ii<nkids-1; ii++){        /* loop over N-1 kids */
+  for (unsigned int ii=0; ii<nkids-1; ii++){        /* loop over N-1 kids */
                                         /* not last kid */
 #ifdef testing
     blurb(ii, kidpid);
-- 
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