From 2b53bca326decd50012883f0cff3b5316a3e100d Mon Sep 17 00:00:00 2001
From: Nicholas Noll <nbnoll@eml.cc>
Date: Tue, 19 Oct 2021 13:28:01 -0700
Subject: feat(rc): prototype of async jobs

---
 sys/cmd/rc/exec.c | 112 ++++++++++++++++++++++++++++++++++++++----------------
 1 file changed, 80 insertions(+), 32 deletions(-)

(limited to 'sys/cmd/rc/exec.c')

diff --git a/sys/cmd/rc/exec.c b/sys/cmd/rc/exec.c
index 87b6bb7..37c289b 100644
--- a/sys/cmd/rc/exec.c
+++ b/sys/cmd/rc/exec.c
@@ -135,6 +135,31 @@ path(char *w)
     return path;
 }
 
+static inline
+void
+defaultsignal(void)
+{
+    signal(SIGINT,  SIG_DFL);
+    signal(SIGQUIT, SIG_DFL);
+    signal(SIGTSTP, SIG_DFL);
+    signal(SIGTTIN, SIG_DFL);
+    signal(SIGTTOU, SIG_DFL);
+    signal(SIGCHLD, SIG_DFL);
+}
+
+static inline
+void
+setpid(int pid)
+{
+    runner->pid = pid;
+    if(runner->pgid <= 0){
+        runner->pgid = runner->pid;
+        addjob(runner);
+    }
+
+    setpgid(pid, runner->pgid);
+}
+
 static
 void
 xx(void)
@@ -161,21 +186,12 @@ xforkx(void)
         return -1;
     case 0: // child
         clearwait(runner);
+        runner->link = nil;
 
         if(shell.interactive){
-            runner->pid = getpid();
-            if(runner->pgid <= 0)
-                runner->pgid = runner->pid;
-
-            setpgid(pid, runner->pgid);
+            setpid(getpid());
             tcsetpgrp(0, runner->pgid);
-
-            signal(SIGINT,  SIG_DFL);
-            signal(SIGQUIT, SIG_DFL);
-            signal(SIGTSTP, SIG_DFL);
-            signal(SIGTTIN, SIG_DFL);
-            signal(SIGTTOU, SIG_DFL);
-            signal(SIGCHLD, SIG_DFL);
+            defaultsignal();
         }
 
         pushword("exec");
@@ -185,12 +201,7 @@ xforkx(void)
         /*unreachable*/
     default: // parent
         addwait(runner, pid);
-
-        /* ensure the state matches for parent and child */
-        runner->pid = pid;
-        if(runner->pgid <= 0)
-            runner->pgid = pid;
-        setpgid(pid, runner->pgid);
+        setpid(pid); // ensure the state matches for parent and child
 
         return pid;
     }
@@ -213,7 +224,7 @@ pushredir(int type, int from, int to)
 /* byte code */
 static
 void
-run(Code *c, int pc, Var *local)
+run(Code *c, int pc, Var *local, int keeppid)
 {
     Thread *new = emalloc(sizeof(*new));
 
@@ -236,7 +247,10 @@ run(Code *c, int pc, Var *local)
     new->wait.on     = nil;
 
     new->status = 0;
-    new->pgid = new->pid = -1;
+    if(keeppid)
+        new->pgid = runner->pgid, new->pid = runner->pid;
+    else
+        new->pgid = new->pid = -1;
 
     new->line     = 0;
     new->link     = runner;
@@ -285,9 +299,9 @@ count(Word *w)
 // -----------------------------------------------------------------------
 // builtins
 
-static Code dotcmd[14] = 
+static Code dotcmd[14] =
 {
-    [0]  = {.i = 1},
+    [0]  = {.i = 0},
     [1]  = {.f = Xmark},
     [2]  = {.f = Xword},
     [3]  = {.s = "0"},
@@ -346,7 +360,7 @@ xdot(void)
     }
     /* set up for a new command loop */
     old = runner; // store pointer to old code
-    run(dotcmd, 1, nil);
+    run(dotcmd, 1, nil, 0);
 
     /* operations on new command stack */
     pushredir(Rclose, fd, 0);
@@ -434,7 +448,7 @@ xboot(int argc, char *argv[])
     bootstrap[i++].f = Xexit;
     bootstrap[i].i = 0;
 
-    run(bootstrap, 1, nil);
+    run(bootstrap, 1, nil, 0);
     pushlist(); // prime bootstrap argv
 
     argv0 = strdup(argv[0]);
@@ -478,7 +492,7 @@ Xreturn(void)
      * 2. return to our calling thread
      * 3. don't free!
      */
-    case PStop:
+     case Prun: case Pstop:
         run->code.i--;
         runner = run->link;
         return;
@@ -487,7 +501,7 @@ Xreturn(void)
      * 1. remove from our list
      * 2. continue to clean up its memory
      */
-    case PDone:
+    case Pdone:
         deljob(run);
         /* fallthrough */
     default:
@@ -589,7 +603,7 @@ Xreadcmd(void)
             --root->code.i;
     }else{
         --root->code.i;    /* re-execute Xreadcmd after codebuf runs */
-        run(compiled, 1, root->local);
+        run(compiled, 1, root->local, 0);
     }
 
     killzombies();
@@ -629,6 +643,43 @@ Xunlocal(void)
     efree(v);
 }
 
+void
+Xasync(void)
+{
+    int pid;
+    int null = open("/dev/null", 0);
+    if(!null){
+        Xerror("can not open /dev/null\n");
+        return;
+    }
+
+    switch(pid=fork()){
+    case -1:
+        close(null);
+        Xerror("fork failed: try again");
+        break;
+
+    case 0: // child
+        clearwait(runner);
+        pushredir(Ropen, null, 0);
+        if(shell.interactive){ // NOTE: this needs to read off its caller's interactivity
+            setpid(getpid());
+            defaultsignal();
+        }
+        run(runner->code.exe, runner->code.i+1, runner->local, 1);
+        runner->link = nil;
+        break;
+
+    default: // parent
+        close(null);
+        setpid(pid);
+        addwait(runner, pid);
+
+        runner->code.i = runner->code.exe[runner->code.i].i; /* jump to end of async command */
+        /* don't wait: continue running */
+    }
+}
+
 void
 Xbasic(void)
 {
@@ -642,7 +693,6 @@ Xbasic(void)
         Xerror("empty argument list\n");
         return;
     }
-    flush(shell.err);
 
     v = var(arg->str);
     if(v->func){
@@ -658,7 +708,6 @@ Xbasic(void)
     }
 
     /* if we are here then it's an external command */
-    addjob(runner);
 
     // run the external command
     if((pid = xforkx()) < 0) {
@@ -666,12 +715,11 @@ Xbasic(void)
         return;
     }
 
-    poplist();
-
     if(!shell.interactive)
         waitall(runner);
 
     foreground(runner, 0); // waits for child
+    poplist();
 }
 
 void
@@ -735,5 +783,5 @@ Xflat(void)
 void
 Xexit(void)
 {
-    exit(shell.status);
+    exit(runner->status);
 }
-- 
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