Remove support for LinuxThreads and vendor 2.4 kernels w/ backported NPTL

Since we now rely on PTRACE_EVENT_CLONE being available (added in
Linux 2.5.46), we're relying on NPTL.

This commit removes the support for older LinuxThreads, as well as the
workarounds for vendor 2.4 kernels with NPTL backported.

 - Rely on tkill being available.

 - Assume gdb doesn't get cancel signals.

 - Remove code that checks the LinuxThreads restart and cancel signals
   in the inferior.

 - Assume that __WALL is available.

 - Assume that non-leader threads report WIFEXITED.

 - Thus, no longer need to send signal 0 to check whether threads are
   still alive.

 - Update comments throughout.

Tested on x86_64 Fedora 20, native and gdbserver.

gdb/ChangeLog:

	* configure.ac: Remove tkill checks.
	* configure, config.in: Regenerate.
	* linux-nat.c: Remove HAVE_TKILL_SYSCALL check.  Update top level
	comments.
	(linux_nat_post_attach_wait): Remove 'cloned' parameter.  Use
	__WALL.
	(attach_proc_task_lwp_callback): Don't set the cloned flag.
	(linux_nat_attach): Adjust.
	(kill_lwp): Remove HAVE_TKILL_SYSCALL check.  No longer fall back
	to 'kill'.
	(linux_handle_extended_wait): Use __WALL.  Don't set the cloned
	flag.
	(wait_lwp): Use __WALL.  Update comments.
	(running_callback, stop_and_resume_callback): Delete.
	(linux_nat_filter_event): Don't stop and resume all lwps. Don't
	check if the event LWP has previously exited.
	(check_zombie_leaders): Update comments.
	(linux_nat_wait_1): Use __WALL.
	(kill_wait_callback): Don't handle clone processes separately.
	Use __WALL instead.
	(linux_thread_alive): Delete.
	(linux_nat_thread_alive): Return true as long as the LWP is in the
	LWP list.
	(linux_nat_update_thread_list): Assume the kernel supports
	PTRACE_EVENT_CLONE.
	(get_signo): Delete.
	(lin_thread_get_thread_signals): Remove LinuxThreads references.
	No longer check __pthread_sig_restart / __pthread_sig_cancel in
	the inferior.
	* linux-nat.h (struct lwp_info) <cloned>: Delete field.
	* linux-thread-db.c: Update comments.
	(_initialize_thread_db): Remove LinuxThreads references.
	* nat/linux-waitpid.c (my_waitpid): No longer emulate __WALL.
	Pass down flags unmodified.
	* linux-waitpid.h (my_waitpid): Update documentation.

gdb/gdbserver/ChangeLog:

	* linux-low.c (linux_kill_one_lwp): Remove references to
	LinuxThreads.
	(kill_lwp): Remove HAVE_TKILL_SYSCALL check.  No longer fall back
	to 'kill'.
	(linux_init_signals): Delete.
	(initialize_low): Adjust.
	* thread-db.c (thread_db_init): Remove LinuxThreads reference.

2 files changed, 6 insertions, 60 deletions

diff --git a/gdb/nat/linux-waitpid.c b/gdb/nat/linux-waitpid.c
index cbcdd95..2d80e0a 100644
--- a/gdb/nat/linux-waitpid.c
+++ b/gdb/nat/linux-waitpid.c
@@ -74,8 +74,7 @@ status_to_str (int status)
   return buf;
 }
 
-/* Wrapper function for waitpid which handles EINTR, and emulates
-   __WALL for systems where that is not available.  */
+/* See linux-waitpid.h.  */
 
 int
 my_waitpid (int pid, int *status, int flags)
@@ -84,64 +83,12 @@ my_waitpid (int pid, int *status, int flags)
 
   linux_debug ("my_waitpid (%d, 0x%x)\n", pid, flags);
 
-  if (flags & __WALL)
+  do
     {
-      sigset_t block_mask, org_mask, wake_mask;
-      int wnohang;
-
-      wnohang = (flags & WNOHANG) != 0;
-      flags &= ~(__WALL | __WCLONE);
-
-      if (!wnohang)
-	{
-	  flags |= WNOHANG;
-
-	  /* Block all signals while here.  This avoids knowing about
-	     LinuxThread's signals.  */
-	  sigfillset (&block_mask);
-	  sigprocmask (SIG_BLOCK, &block_mask, &org_mask);
-
-	  /* ... except during the sigsuspend below.  */
-	  sigemptyset (&wake_mask);
-	}
-
-      while (1)
-	{
-	  /* Since all signals are blocked, there's no need to check
-	     for EINTR here.  */
-	  ret = waitpid (pid, status, flags);
-	  out_errno = errno;
-
-	  if (ret == -1 && out_errno != ECHILD)
-	    break;
-	  else if (ret > 0)
-	    break;
-
-	  if (flags & __WCLONE)
-	    {
-	      /* We've tried both flavors now.  If WNOHANG is set,
-		 there's nothing else to do, just bail out.  */
-	      if (wnohang)
-		break;
-
-	      linux_debug ("blocking\n");
-
-	      /* Block waiting for signals.  */
-	      sigsuspend (&wake_mask);
-	    }
-	  flags ^= __WCLONE;
-	}
-
-      if (!wnohang)
-	sigprocmask (SIG_SETMASK, &org_mask, NULL);
-    }
-  else
-    {
-      do
-	ret = waitpid (pid, status, flags);
-      while (ret == -1 && errno == EINTR);
-      out_errno = errno;
+      ret = waitpid (pid, status, flags);
     }
+  while (ret == -1 && errno == EINTR);
+  out_errno = errno;
 
   linux_debug ("my_waitpid (%d, 0x%x): status(%x), %d\n",
 	       pid, flags, (ret > 0 && status != NULL) ? *status : -1, ret);
diff --git a/gdb/nat/linux-waitpid.h b/gdb/nat/linux-waitpid.h
index bc5e8d2..1a15fdc 100644
--- a/gdb/nat/linux-waitpid.h
+++ b/gdb/nat/linux-waitpid.h
@@ -20,8 +20,7 @@
 #ifndef LINUX_WAITPID_H
 #define LINUX_WAITPID_H
 
-/* Wrapper function for waitpid which handles EINTR, and emulates
-   __WALL for systems where that is not available.  */
+/* Wrapper function for waitpid which handles EINTR.  */
 extern int my_waitpid (int pid, int *status, int flags);
 
 /* Convert wait status STATUS to a string.  Used for printing debug