[v4,1/2,BZ,21340] add support for POSIX_SPAWN_SETSID

diff --git a/posix/Makefile b/posix/Makefile
index a6586ea..0fc509c 100644
--- a/posix/Makefile
+++ b/posix/Makefile
@@ -91,7 +91,7 @@  tests		:= test-errno tstgetopt testfnm runtests runptests \
 		   bug-getopt5 tst-getopt_long1 bug-regex34 bug-regex35 \
 		   tst-pathconf tst-getaddrinfo4 tst-rxspencer-no-utf8 \
 		   tst-fnmatch3 bug-regex36 tst-getaddrinfo5 \
-		   tst-posix_spawn-fd \
+		   tst-posix_spawn-fd tst-posix_spawn-setsid \
 		   tst-posix_fadvise tst-posix_fadvise64
 xtests		:= bug-ga2
 ifeq (yes,$(build-shared))
diff --git a/posix/spawn.h b/posix/spawn.h
index 36e3867..a1154a3 100644
--- a/posix/spawn.h
+++ b/posix/spawn.h
@@ -59,6 +59,7 @@  typedef struct
 #define POSIX_SPAWN_SETSCHEDULER	0x20
 #ifdef __USE_GNU
 # define POSIX_SPAWN_USEVFORK		0x40
+# define POSIX_SPAWN_SETSID		0x80
 #endif
 
 
diff --git a/posix/spawnattr_setflags.c b/posix/spawnattr_setflags.c
index 9b3d1e0..62d2f00 100644
--- a/posix/spawnattr_setflags.c
+++ b/posix/spawnattr_setflags.c
@@ -25,6 +25,7 @@ 
 		   | POSIX_SPAWN_SETSIGMASK				      \
 		   | POSIX_SPAWN_SETSCHEDPARAM				      \
 		   | POSIX_SPAWN_SETSCHEDULER				      \
+		   | POSIX_SPAWN_SETSID					      \
 		   | POSIX_SPAWN_USEVFORK)
 
 /* Store flags in the attribute structure.  */
diff --git a/posix/tst-posix_spawn-setsid.c b/posix/tst-posix_spawn-setsid.c
new file mode 100644
index 0000000..256bd72
--- /dev/null
+++ b/posix/tst-posix_spawn-setsid.c
@@ -0,0 +1,95 @@ 
+/* Test posix_spawn setsid attribute.
+   Copyright (C) 2017 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <spawn.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <sys/resource.h>
+#include <unistd.h>
+
+#include <support/check.h>
+
+static void
+do_test_setsid (bool test_setsid)
+{
+  pid_t sid, child_sid;
+  int res;
+
+  /* Current session ID.  */
+  sid = getsid(0);
+  if (sid == (pid_t) -1)
+    FAIL_EXIT1 ("getsid (0): %m");
+
+  posix_spawnattr_t attrp;
+  /* posix_spawnattr_init should not fail (it basically memset the
+     attribute).  */
+  posix_spawnattr_init (&attrp);
+  if (test_setsid)
+    {
+      res = posix_spawnattr_setflags (&attrp, POSIX_SPAWN_SETSID);
+      if (res != 0)
+	{
+	  errno = res;
+	  FAIL_EXIT1 ("posix_spawnattr_setflags: %m");
+	}
+    }
+
+  /* Program to run.  */
+  char *args[2] = { (char *) "true", NULL };
+  pid_t child;
+
+  res = posix_spawnp (&child, "true", NULL, &attrp, args, environ);
+  /* posix_spawnattr_destroy is noop.  */
+  posix_spawnattr_destroy (&attrp);
+
+  if (res != 0)
+    {
+      errno = res;
+      FAIL_EXIT1 ("posix_spawnp: %m");
+    }
+
+  /* Child should have a different session ID than parent.  */
+  child_sid = getsid (child);
+
+  if (child_sid == (pid_t) -1)
+    FAIL_EXIT1 ("getsid (%i): %m", child);
+
+  if (test_setsid)
+    {
+      if (child_sid == sid)
+	FAIL_EXIT1 ("child session ID matched parent one");
+    }
+  else
+    {
+      if (child_sid != sid)
+	FAIL_EXIT1 ("child session ID did not match parent one");
+    }
+}
+
+static int
+do_test (void)
+{
+  do_test_setsid (false);
+  do_test_setsid (true);
+
+  return 0;
+}
+
+#include <support/test-driver.c>
diff --git a/sysdeps/mach/hurd/spawni.c b/sysdeps/mach/hurd/spawni.c
index 284875a..7430383 100644
--- a/sysdeps/mach/hurd/spawni.c
+++ b/sysdeps/mach/hurd/spawni.c
@@ -281,6 +281,9 @@  __spawni (pid_t *pid, const char *file,
     }
 #endif
 
+  if (!err && (flags & POSIX_SPAWN_SETSID) != 0)
+    err = __proc_setsid (proc);
+
   /* Set the process group ID.  */
   if (!err && (flags & POSIX_SPAWN_SETPGROUP) != 0)
     err = __proc_setpgrp (proc, new_pid, attrp->__pgrp);
diff --git a/sysdeps/posix/spawni.c b/sysdeps/posix/spawni.c
index 5cc2ad1..9cad25c 100644
--- a/sysdeps/posix/spawni.c
+++ b/sysdeps/posix/spawni.c
@@ -101,7 +101,8 @@  __spawni (pid_t *pid, const char *file,
 	 to POSIX.  */
       || ((flags & (POSIX_SPAWN_SETSIGMASK | POSIX_SPAWN_SETSIGDEF
 		    | POSIX_SPAWN_SETSCHEDPARAM | POSIX_SPAWN_SETSCHEDULER
-		    | POSIX_SPAWN_SETPGROUP | POSIX_SPAWN_RESETIDS)) == 0
+		    | POSIX_SPAWN_SETPGROUP | POSIX_SPAWN_RESETIDS
+		    | POSIX_SPAWN_SETSID)) == 0
 	  && file_actions == NULL))
     new_pid = __vfork ();
   else
@@ -159,6 +160,10 @@  __spawni (pid_t *pid, const char *file,
     }
 #endif
 
+  if ((flags & POSIX_SPAWN_SETSID) != 0
+      && __setsid () < 0)
+    _exit (SPAWN_ERROR);
+
   /* Set the process group ID.  */
   if ((flags & POSIX_SPAWN_SETPGROUP) != 0
       && __setpgid (0, attrp->__pgrp) != 0)
diff --git a/sysdeps/unix/sysv/linux/spawni.c b/sysdeps/unix/sysv/linux/spawni.c
index d7f9e83..fc5d170 100644
--- a/sysdeps/unix/sysv/linux/spawni.c
+++ b/sysdeps/unix/sysv/linux/spawni.c
@@ -177,6 +177,10 @@  __spawni_child (void *arguments)
     }
 #endif
 
+  if ((attr->__flags & POSIX_SPAWN_SETSID) != 0
+      && (setsid () < 0))
+    goto fail;
+
   /* Set the process group ID.  */
   if ((attr->__flags & POSIX_SPAWN_SETPGROUP) != 0
       && (ret = __setpgid (0, attr->__pgrp)) != 0)