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.

1 files changed, 16 insertions, 44 deletions

diff --git a/gdb/gdbserver/linux-low.c b/gdb/gdbserver/linux-low.c
index 5e2dc58..edff916 100644
--- a/gdb/gdbserver/linux-low.c
+++ b/gdb/gdbserver/linux-low.c
@@ -878,10 +878,6 @@ linux_create_inferior (char *program, char **allargs)
       close_most_fds ();
       ptrace (PTRACE_TRACEME, 0, (PTRACE_TYPE_ARG3) 0, (PTRACE_TYPE_ARG4) 0);
 
-#ifndef __ANDROID__ /* Bionic doesn't use SIGRTMIN the way glibc does.  */
-      signal (__SIGRTMIN + 1, SIG_DFL);
-#endif
-
       setpgid (0, 0);
 
       /* If gdbserver is connected to gdb via stdio, redirect the inferior's
@@ -1183,13 +1179,12 @@ linux_kill_one_lwp (struct lwp_info *lwp)
      ptrace(CONT, pid, 0,0) and just resumes the tracee.  A better
      alternative is to kill with SIGKILL.  We only need one SIGKILL
      per process, not one for each thread.  But since we still support
-     linuxthreads, and we also support debugging programs using raw
-     clone without CLONE_THREAD, we send one for each thread.  For
-     years, we used PTRACE_KILL only, so we're being a bit paranoid
-     about some old kernels where PTRACE_KILL might work better
-     (dubious if there are any such, but that's why it's paranoia), so
-     we try SIGKILL first, PTRACE_KILL second, and so we're fine
-     everywhere.  */
+     support debugging programs using raw clone without CLONE_THREAD,
+     we send one for each thread.  For years, we used PTRACE_KILL
+     only, so we're being a bit paranoid about some old kernels where
+     PTRACE_KILL might work better (dubious if there are any such, but
+     that's why it's paranoia), so we try SIGKILL first, PTRACE_KILL
+     second, and so we're fine everywhere.  */
 
   errno = 0;
   kill_lwp (pid, SIGKILL);
@@ -3320,8 +3315,6 @@ linux_wait_1 (ptid_t ptid,
      stepping - they may require special handling to skip the signal
      handler. Also never ignore signals that could be caused by a
      breakpoint.  */
-  /* FIXME drow/2002-06-09: Get signal numbers from the inferior's
-     thread library?  */
   if (WIFSTOPPED (w)
       && current_thread->last_resume_kind != resume_step
       && (
@@ -3663,27 +3656,17 @@ linux_wait (ptid_t ptid,
 static int
 kill_lwp (unsigned long lwpid, int signo)
 {
-  /* Use tkill, if possible, in case we are using nptl threads.  If tkill
-     fails, then we are not using nptl threads and we should be using kill.  */
-
-#ifdef __NR_tkill
-  {
-    static int tkill_failed;
-
-    if (!tkill_failed)
-      {
-	int ret;
-
-	errno = 0;
-	ret = syscall (__NR_tkill, lwpid, signo);
-	if (errno != ENOSYS)
-	  return ret;
-	tkill_failed = 1;
-      }
-  }
-#endif
+  int ret;
 
-  return kill (lwpid, signo);
+  errno = 0;
+  ret = syscall (__NR_tkill, lwpid, signo);
+  if (errno == ENOSYS)
+    {
+      /* If tkill fails, then we are not using nptl threads, a
+	 configuration we no longer support.  */
+      perror_with_name (("tkill"));
+    }
+  return ret;
 }
 
 void
@@ -7196,16 +7179,6 @@ static struct target_ops linux_target_ops = {
   linux_supports_software_single_step
 };
 
-static void
-linux_init_signals ()
-{
-  /* FIXME drow/2002-06-09: As above, we should check with LinuxThreads
-     to find what the cancel signal actually is.  */
-#ifndef __ANDROID__ /* Bionic doesn't use SIGRTMIN the way glibc does.  */
-  signal (__SIGRTMIN+1, SIG_IGN);
-#endif
-}
-
 #ifdef HAVE_LINUX_REGSETS
 void
 initialize_regsets_info (struct regsets_info *info)
@@ -7225,7 +7198,6 @@ initialize_low (void)
   memset (&sigchld_action, 0, sizeof (sigchld_action));
   set_target_ops (&linux_target_ops);
 
-  linux_init_signals ();
   linux_ptrace_init_warnings ();
 
   sigchld_action.sa_handler = sigchld_handler;