erts: Create forker process for spawn driver

Instead of forking from the beam process, we create a separate
process in which all forks are done. This has several advantages:

1) performance:
  * don't have to close all fd's in the world
  * fork only has to copy stuff from a small process
  * work is done in a completely seperate process
  * a 3x performance increase has been measured,
    can be made even greater (10x) if we cache the
    environment in child setup

2) stability
  * the exec is done in another process than beam, which means that
    if the file that we exec to is on an nfs that is not available
    right now we will not block a scheduler until the nfs returns.

3) simplicity
  * don't have to deal with SIGCHLD in the erts

Unfortunately, this solution also implies some badness.

1) There will always be a seperate process running together with
   beam on unix. This could be confusing and undesirable.
2) We have to transfer the entire environment to child_setup
   for each command.

OTP-13088

1 files changed, 59 insertions, 8 deletions

diff --git a/erts/emulator/beam/io.c b/erts/emulator/beam/io.c
index 2a3759212e..6ec7a9ba1e 100644
--- a/erts/emulator/beam/io.c
+++ b/erts/emulator/beam/io.c
@@ -54,6 +54,7 @@
 extern ErlDrvEntry fd_driver_entry;
 extern ErlDrvEntry vanilla_driver_entry;
 extern ErlDrvEntry spawn_driver_entry;
+extern ErlDrvEntry forker_driver_entry;
 extern ErlDrvEntry *driver_tab[]; /* table of static drivers, only used during initialization */
 
 erts_driver_t *driver_list; /* List of all drivers, static and dynamic. */
@@ -71,6 +72,7 @@ const Port erts_invalid_port = {{ERTS_INVALID_PORT}};
 
 erts_driver_t vanilla_driver;
 erts_driver_t spawn_driver;
+erts_driver_t forker_driver;
 erts_driver_t fd_driver;
 
 int erts_port_synchronous_ops = 0;
@@ -306,12 +308,9 @@ static Port *create_port(char *name,
     size_t port_size, busy_port_queue_size, size;
     erts_aint32_t state = ERTS_PORT_SFLG_CONNECTED;
     erts_aint32_t x_pts_flgs = 0;
-#ifdef DEBUG
-    /* Make sure the debug flags survives until port is freed */
-    state |= ERTS_PORT_SFLG_PORT_DEBUG;
-#endif
 
 #ifdef ERTS_SMP
+    ErtsRunQueue *runq;
     if (!driver_lock) {
 	/* Align size for mutex following port struct */
 	port_size = size = ERTS_ALC_DATA_ALIGN_SIZE(sizeof(Port));
@@ -321,6 +320,12 @@ static Port *create_port(char *name,
 #endif
 	port_size = size = ERTS_ALC_DATA_ALIGN_SIZE(sizeof(Port));
 
+#ifdef DEBUG
+    /* Make sure the debug flags survives until port is freed */
+    state |= ERTS_PORT_SFLG_PORT_DEBUG;
+#endif
+
+
     busy_port_queue_size
 	= ((driver->flags & ERL_DRV_FLAG_NO_BUSY_MSGQ)
 	   ? 0
@@ -356,8 +361,12 @@ static Port *create_port(char *name,
 	p += sizeof(erts_mtx_t);
 	state |= ERTS_PORT_SFLG_PORT_SPECIFIC_LOCK;
     }
-    erts_smp_atomic_set_nob(&prt->run_queue,
-			    (erts_aint_t) erts_get_runq_current(NULL));
+    if (erts_get_scheduler_data())
+        runq = erts_get_runq_current(NULL);
+    else
+        runq = ERTS_RUNQ_IX(0);
+    erts_smp_atomic_set_nob(&prt->run_queue, (erts_aint_t) runq);
+
     prt->xports = NULL;
 #else
     erts_atomic32_init_nob(&prt->refc, 1);
@@ -1535,6 +1544,26 @@ erts_schedule_proc2port_signal(Process *c_p,
     return ERTS_PORT_OP_SCHEDULED;
 }
 
+static int
+erts_schedule_port2port_signal(Eterm port_num, ErtsProc2PortSigData *sigdp,
+                               int task_flags,
+                               ErtsProc2PortSigCallback callback)
+{
+    Port *prt = erts_port_lookup_raw(port_num);
+
+    if (!prt)
+        return -1;
+
+    sigdp->caller = ERTS_INVALID_PID;
+
+    return erts_port_task_schedule(prt->common.id,
+                                   NULL,
+                                   ERTS_PORT_TASK_PROC_SIG,
+                                   sigdp,
+                                   callback,
+                                   task_flags);
+}
+
 static ERTS_INLINE void
 send_badsig(Port *prt) {
     ErtsProcLocks rp_locks = ERTS_PROC_LOCKS_XSIG_SEND;
@@ -2862,6 +2891,7 @@ void erts_init_io(int port_tab_size,
     init_driver(&fd_driver, &fd_driver_entry, NULL);
     init_driver(&vanilla_driver, &vanilla_driver_entry, NULL);
     init_driver(&spawn_driver, &spawn_driver_entry, NULL);
+    init_driver(&forker_driver, &forker_driver_entry, NULL);
     erts_init_static_drivers();
     for (dp = driver_tab; *dp != NULL; dp++)
 	erts_add_driver_entry(*dp, NULL, 1);
@@ -2923,6 +2953,7 @@ void erts_lcnt_enable_io_lock_count(int enable) {
 
     lcnt_enable_drv_lock_count(&vanilla_driver, enable);
     lcnt_enable_drv_lock_count(&spawn_driver, enable);
+    lcnt_enable_drv_lock_count(&forker_driver, enable);
     lcnt_enable_drv_lock_count(&fd_driver, enable);
     /* enable lock counting in all drivers */
     for (dp = driver_list; dp; dp = dp->next) {
@@ -3964,7 +3995,7 @@ port_sig_control(Port *prt,
 	    Uint hsz, rsz;
 	    int control_flags;
 
-	    rp = erts_proc_lookup_raw(sigdp->caller);
+	    rp = sigdp->caller == ERTS_INVALID_PID ? NULL : erts_proc_lookup_raw(sigdp->caller);
 	    if (!rp)
 		goto done;
 
@@ -4007,7 +4038,8 @@ port_sig_control(Port *prt,
 
     /* failure */
 
-    port_sched_op_reply(sigdp->caller, sigdp->ref, am_badarg);
+    if (sigdp->caller != ERTS_INVALID_PID)
+        port_sched_op_reply(sigdp->caller, sigdp->ref, am_badarg);
 
 done:
 
@@ -4017,6 +4049,23 @@ done:
     return ERTS_PORT_REDS_CONTROL;
 }
 
+/*
+ * This is an asynchronous control call. I.e. it will not return anything
+ * to the caller.
+ */
+int
+erl_drv_port_control(Eterm port_num, char cmd, char* buff, ErlDrvSizeT size)
+{
+    ErtsProc2PortSigData *sigdp = erts_port_task_alloc_p2p_sig_data();
+
+    sigdp->flags = ERTS_P2P_SIG_TYPE_CONTROL | ERTS_P2P_SIG_DATA_FLG_REPLY;
+    sigdp->u.control.binp = NULL;
+    sigdp->u.control.command = cmd;
+    sigdp->u.control.bufp = buff;
+    sigdp->u.control.size = size;
+
+    return erts_schedule_port2port_signal(port_num, sigdp, 0, port_sig_control);
+}
 
 ErtsPortOpResult
 erts_port_control(Process* c_p,
@@ -4794,6 +4843,8 @@ print_port_info(Port *p, int to, void *arg)
 	erts_print(to, arg, "Port is a file: %s\n",p->name);
     } else if (p->drv_ptr == &spawn_driver) {
 	erts_print(to, arg, "Port controls external process: %s\n",p->name);
+    } else if (p->drv_ptr == &forker_driver) {
+	erts_print(to, arg, "Port controls forker process: %s\n",p->name);
     } else {
 	erts_print(to, arg, "Port controls linked-in driver: %s\n",p->name);
     }