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, 7 insertions, 42 deletions

diff --git a/erts/emulator/sys/unix/erl_unix_sys.h b/erts/emulator/sys/unix/erl_unix_sys.h
index a11a44c259..c46f2c1fa2 100644
--- a/erts/emulator/sys/unix/erl_unix_sys.h
+++ b/erts/emulator/sys/unix/erl_unix_sys.h
@@ -30,9 +30,7 @@
 #include <limits.h>
 #include <stdlib.h>
 #include <string.h>
-#ifndef QNX
 #include <memory.h>
-#endif
 
 #if defined(__sun__) && defined(__SVR4) && !defined(__EXTENSIONS__)
 #   define __EXTENSIONS__
@@ -92,11 +90,6 @@
 #include <ieeefp.h>
 #endif
 
-#ifdef QNX
-#include <process.h>
-#include <sys/qnx_glob.h>
-#endif
-
 #include <pwd.h>
 
 #ifndef HZ
@@ -136,13 +129,6 @@
 #  define ERTS_POLL_NEED_ASYNC_INTERRUPT_SUPPORT
 #endif
 
-#ifndef ENABLE_CHILD_WAITER_THREAD
-#  ifdef ERTS_SMP
-#    define ERTS_SMP_SCHEDULERS_NEED_TO_CHECK_CHILDREN
-void erts_check_children(void);
-#  endif
-#endif
-
 typedef void *GETENV_STATE;
 
 /*
@@ -310,7 +296,6 @@ typedef void (*SIGFUNC)(int);
 extern SIGFUNC sys_signal(int, SIGFUNC);
 extern void sys_sigrelease(int);
 extern void sys_sigblock(int);
-extern void sys_stop_cat(void);
 
 /*
  * Handling of floating point exceptions.
@@ -425,18 +410,14 @@ void erts_sys_unblock_fpe(int);
 #define ERTS_FP_ERROR_THOROUGH(p, f, A)	__ERTS_FP_ERROR_THOROUGH(&(p)->fp_exception, f, A)
 
 
-#ifdef NEED_CHILD_SETUP_DEFINES
-/* The child setup argv[] */
-#define CS_ARGV_PROGNAME_IX	0		/* Program name		*/
-#define CS_ARGV_UNBIND_IX	1		/* Unbind from cpu	*/
-#define CS_ARGV_WD_IX		2		/* Working directory	*/
-#define CS_ARGV_CMD_IX		3		/* Command		*/
-#define CS_ARGV_FD_CR_IX	4		/* Fd close range	*/
-#define CS_ARGV_DUP2_OP_IX(N)	((N) + 5)	/* dup2 operations	*/
+#define FORKER_ARGV_NO_OF_ARGS  3
+#define FORKER_ARGV_PROGNAME_IX	0    /* Program name                          */
+#define FORKER_ARGV_MAX_FILES	1    /* max_files                             */
 
-#define CS_ARGV_NO_OF_DUP2_OPS	3		/* Number of dup2 ops	*/
-#define CS_ARGV_NO_OF_ARGS	8		/* Number of arguments	*/
-#endif /* #ifdef NEED_CHILD_SETUP_DEFINES */
+#define FORKER_FLAG_USE_STDIO   (1 << 0)    /* dup the pipe to stdin/stderr   */
+#define FORKER_FLAG_EXIT_STATUS (1 << 1)    /* send the exit status to parent */
+#define FORKER_FLAG_DO_READ     (1 << 2)    /* dup write fd */
+#define FORKER_FLAG_DO_WRITE    (1 << 3)    /* dup read fd  */
 
 /* Threads */
 #ifdef USE_THREADS
@@ -470,20 +451,4 @@ extern jmp_buf erts_sys_sigsegv_jmp;
     } while(0)
 #endif
 
-#ifdef USE_THREADS
-#  ifdef ENABLE_CHILD_WAITER_THREAD
-#    define CHLDWTHR ENABLE_CHILD_WAITER_THREAD
-#  else
-#    define CHLDWTHR 0
-#  endif
-#  define FDBLOCK 1
-#else
-#  define CHLDWTHR 0
-#  define FDBLOCK 0
-#endif
-
-#define ERTS_SYS_SUSPEND_SIGNAL SIGUSR2
-
-int check_children(void);
-
 #endif /* #ifndef _ERL_UNIX_SYS_H */