posix: Correctly enable/disable cancellation on Linux posix_spawn

This patch correctly enable and disable asynchronous cancellation on
Linux posix_spawn.  Current code invert the logic by enabling and
disabling instead.  It also adds a new test to check if posix_spawn
is not a cancellation entrypoint.

Checked on x86_64, i686, powerpc64le, and aarch64.

	* nptl/Makefile (tests): Add tst-exec5.
	* nptl/tst-exec5.c: New file.
	* sysdeps/unix/sysv/linux/spawni.c (__spawni): Correctly enable and disable
	asynchronous cancellation.

ChangeLog

@@ -1,3 +1,10 @@
+2016-09-20  Adhemerval Zanella  <adhemerval.zanella@linaro.org>
+
+	* nptl/Makefile (tests): Add tst-exec5.
+	* nptl/tst-exec5.c: New file.
+	* sysdeps/unix/sysv/linux/spawni.c (__spawni): Correctly enable and disable
+	asynchronous cancellation.
+
 2016-09-20  Samuel Thibault  <samuel.thibault@ens-lyon.org>
 
 	* hurd/exc2signal.c: #include <hurd/signal.h>

nptl/Makefile

@@ -273,7 +273,7 @@ tests = tst-typesizes \
 	tst-flock1 tst-flock2 \
 	tst-signal1 tst-signal2 tst-signal3 tst-signal4 tst-signal5 \
 	tst-signal6 tst-signal7 \
-	tst-exec1 tst-exec2 tst-exec3 tst-exec4 \
+	tst-exec1 tst-exec2 tst-exec3 tst-exec4 tst-exec5 \
 	tst-exit1 tst-exit2 tst-exit3 \
 	tst-stdio1 tst-stdio2 \
 	tst-stack1 tst-stack2 tst-stack3 tst-stack4 tst-pthread-getattr \

nptl/tst-exec5.c

@@ -0,0 +1,176 @@
+/* Check if posix_spawn does not act as a cancellation entrypoint.
+   Copyright (C) 2016 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 <paths.h>
+#include <pthread.h>
+#include <signal.h>
+#include <spawn.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <sys/wait.h>
+
+static int do_test (void);
+#define TEST_FUNCTION do_test ()
+#include <test-skeleton.c>
+
+static pthread_barrier_t b;
+
+static pid_t pid;
+static int pipefd[2];
+
+static void *
+tf (void *arg)
+{
+  xpthread_barrier_wait (&b);
+
+  posix_spawn_file_actions_t a;
+  if (posix_spawn_file_actions_init (&a) != 0)
+    {
+      puts ("error: spawn_file_actions_init failed");
+      exit (1);
+    }
+
+  if (posix_spawn_file_actions_adddup2 (&a, pipefd[1], STDOUT_FILENO) != 0)
+    {
+      puts ("error: spawn_file_actions_adddup2 failed");
+      exit (1);
+    }
+
+  if (posix_spawn_file_actions_addclose (&a, pipefd[0]) != 0)
+    {
+      puts ("error: spawn_file_actions_addclose");
+      exit (1);
+    }
+
+  char *argv[] = { (char *) _PATH_BSHELL, (char *) "-c", (char *) "echo $$",
+		   NULL };
+  if (posix_spawn (&pid, _PATH_BSHELL, &a, NULL, argv, NULL) != 0)
+    {
+      puts ("error: spawn failed");
+      exit (1);
+    }
+
+  return NULL;
+}
+
+
+static int
+do_test (void)
+{
+  /* The test basically pipe a 'echo $$' created by a thread with a
+     cancellation pending.  It then checks if the thread is not cancelled,
+     the process is created and if the output is the expected one.  */
+
+  if (pipe (pipefd) != 0)
+    {
+      puts ("error: pipe failed");
+      exit (1);
+    }
+
+  /* Not interested in knowing when the pipe is closed.  */
+  if (sigignore (SIGPIPE) != 0)
+    {
+      puts ("error: sigignore failed");
+      exit (1);
+    }
+
+  /* To synchronize with the thread.  */
+  if (pthread_barrier_init (&b, NULL, 2) != 0)
+    {
+      puts ("error: pthread_barrier_init failed");
+      exit (1);
+    }
+
+  pthread_t th = xpthread_create (NULL, &tf, NULL);
+
+  if (pthread_cancel (th) != 0)
+    {
+      puts ("error: pthread_cancel failed");
+      return 1;
+    }
+
+  xpthread_barrier_wait (&b);
+
+  if (xpthread_join (th) == PTHREAD_CANCELED)
+    {
+      puts ("error: thread cancelled");
+      exit (1);
+    }
+
+  close (pipefd[1]);
+
+  /* The global 'pid' should be set by thread posix_spawn calling.  Check
+     below if it was executed correctly and with expected output.  */
+
+  char buf[64];
+  ssize_t n;
+  bool seen_pid = false;
+  while (TEMP_FAILURE_RETRY ((n = read (pipefd[0], buf, sizeof (buf)))) > 0)
+    {
+      /* We only expect to read the PID.  */
+      char *endp;
+      long int rpid = strtol (buf, &endp, 10);
+
+      if (*endp != '\n')
+	{
+	  printf ("error: didn't parse whole line: \"%s\"\n", buf);
+	  exit (1);
+	}
+      if (endp == buf)
+	{
+	  puts ("error: read empty line");
+	  exit (1);
+	}
+
+      if (rpid != pid)
+	{
+	  printf ("error: found \"%s\", expected PID %ld\n", buf,
+		 (long int) pid);
+	  exit (1);
+	}
+
+      if (seen_pid)
+	{
+	  puts ("error: found more than one PID line");
+	  exit (1);
+	}
+
+      seen_pid = true;
+    }
+
+  close (pipefd[0]);
+
+  int status;
+  int err = waitpid (pid, &status, 0);
+  if (err != pid)
+    {
+      puts ("errnor: waitpid failed");
+      exit (1);
+    }
+
+  if (!seen_pid)
+    {
+      puts ("error: didn't get PID");
+      exit (1);
+    }
+
+  return 0;
+}

sysdeps/unix/sysv/linux/spawni.c

@@ -340,7 +340,9 @@ __spawnix (pid_t * pid, const char *file,
     }
 
   /* Disable asynchronous cancellation.  */
-  int cs = LIBC_CANCEL_ASYNC ();
+  int state;
+  __libc_ptf_call (__pthread_setcancelstate,
+                   (PTHREAD_CANCEL_DISABLE, &state), 0);
 
   args.file = file;
   args.exec = exec;
@@ -386,7 +388,7 @@ __spawnix (pid_t * pid, const char *file,
 
   __sigprocmask (SIG_SETMASK, &args.oldmask, 0);
 
-  LIBC_CANCEL_RESET (cs);
+  __libc_ptf_call (__pthread_setcancelstate, (state, NULL), 0);
 
   return ec;
 }