X-Git-Url: http://git.efficios.com/?a=blobdiff_plain;f=gdb%2Flinux-thread-db.c;h=006ba411331e6431586ded9529b4246d46194562;hb=48cb83fdd097716c0f21511e0e5b475bb1f2aa41;hp=c49c89585b4f7ae7b2edc2bafca63822009c825e;hpb=28b1733311240d4ef1b0776b5030acb499c3321c;p=deliverable%2Fbinutils-gdb.git

diff --git a/gdb/linux-thread-db.c b/gdb/linux-thread-db.c
index c49c89585b..006ba41133 100644
--- a/gdb/linux-thread-db.c
+++ b/gdb/linux-thread-db.c
@@ -1,13 +1,13 @@
 /* libthread_db assisted debugging support, generic parts.
 
-   Copyright (C) 1999, 2000, 2001, 2003, 2004, 2005, 2006
-   Free Software Foundation, Inc.
+   Copyright (C) 1999, 2000, 2001, 2003, 2004, 2005, 2006, 2007, 2008, 2009,
+   2010 Free Software Foundation, Inc.
 
    This file is part of GDB.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
-   the Free Software Foundation; either version 2 of the License, or
+   the Free Software Foundation; either version 3 of the License, or
    (at your option) any later version.
 
    This program is distributed in the hope that it will be useful,
@@ -16,9 +16,7 @@
    GNU General Public License for more details.
 
    You should have received a copy of the GNU General Public License
-   along with this program; if not, write to the Free Software
-   Foundation, Inc., 51 Franklin Street, Fifth Floor,
-   Boston, MA 02110-1301, USA.  */
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
 
 #include "defs.h"
 
@@ -28,44 +26,60 @@
 #include "gdb_thread_db.h"
 
 #include "bfd.h"
+#include "command.h"
 #include "exceptions.h"
+#include "gdbcmd.h"
 #include "gdbthread.h"
 #include "inferior.h"
 #include "symfile.h"
 #include "objfiles.h"
 #include "target.h"
 #include "regcache.h"
+#include "solib.h"
 #include "solib-svr4.h"
 #include "gdbcore.h"
+#include "observer.h"
 #include "linux-nat.h"
 
+#include <signal.h>
+
 #ifdef HAVE_GNU_LIBC_VERSION_H
 #include <gnu/libc-version.h>
 #endif
 
-#ifndef LIBTHREAD_DB_SO
-#define LIBTHREAD_DB_SO "libthread_db.so.1"
-#endif
+/* GNU/Linux libthread_db support.
 
-/* If we're running on GNU/Linux, we must explicitly attach to any new
-   threads.  */
+   libthread_db is a library, provided along with libpthread.so, which
+   exposes the internals of the thread library to a debugger.  It
+   allows GDB to find existing threads, new threads as they are
+   created, thread IDs (usually, the result of pthread_self), and
+   thread-local variables.
 
-/* FIXME: There is certainly some room for improvements:
-   - Cache LWP ids.
-   - Bypass libthread_db when fetching or storing registers for
-   threads bound to a LWP.  */
+   The libthread_db interface originates on Solaris, where it is
+   both more powerful and more complicated.  This implementation
+   only works for LinuxThreads and NPTL, the two glibc threading
+   libraries.  It assumes that each thread is permanently assigned
+   to a single light-weight process (LWP).
 
-/* This module's target vector.  */
-static struct target_ops thread_db_ops;
+   libthread_db-specific information is stored in the "private" field
+   of struct thread_info.  When the field is NULL we do not yet have
+   information about the new thread; this could be temporary (created,
+   but the thread library's data structures do not reflect it yet)
+   or permanent (created using clone instead of pthread_create).
 
-/* The target vector that we call for things this module can't handle.  */
-static struct target_ops *target_beneath;
+   Process IDs managed by linux-thread-db.c match those used by
+   linux-nat.c: a common PID for all processes, an LWP ID for each
+   thread, and no TID.  We save the TID in private.  Keeping it out
+   of the ptid_t prevents thread IDs changing when libpthread is
+   loaded or unloaded.  */
 
-/* Pointer to the next function on the objfile event chain.  */
-static void (*target_new_objfile_chain) (struct objfile * objfile);
+static char *libthread_db_search_path;
+
+/* If we're running on GNU/Linux, we must explicitly attach to any new
+   threads.  */
 
-/* Non-zero if we're using this module's target vector.  */
-static int using_thread_db;
+/* This module's target vector.  */
+static struct target_ops thread_db_ops;
 
 /* Non-zero if we have determined the signals used by the threads
    library.  */
@@ -73,72 +87,153 @@ static int thread_signals;
 static sigset_t thread_stop_set;
 static sigset_t thread_print_set;
 
-/* Structure that identifies the child process for the
-   <proc_service.h> interface.  */
-static struct ps_prochandle proc_handle;
+struct thread_db_info
+{
+  struct thread_db_info *next;
+
+  /* Process id this object refers to.  */
+  int pid;
+
+  /* Handle from dlopen for libthread_db.so.  */
+  void *handle;
+
+  /* Structure that identifies the child process for the
+     <proc_service.h> interface.  */
+  struct ps_prochandle proc_handle;
 
-/* Connection to the libthread_db library.  */
-static td_thragent_t *thread_agent;
+  /* Connection to the libthread_db library.  */
+  td_thragent_t *thread_agent;
 
-/* Pointers to the libthread_db functions.  */
+  /* True if we need to apply the workaround for glibc/BZ5983.  When
+     we catch a PTRACE_O_TRACEFORK, and go query the child's thread
+     list, nptl_db returns the parent's threads in addition to the new
+     (single) child thread.  If this flag is set, we do extra work to
+     be able to ignore such stale entries.  */
+  int need_stale_parent_threads_check;
 
-static td_err_e (*td_init_p) (void);
+  /* Location of the thread creation event breakpoint.  The code at
+     this location in the child process will be called by the pthread
+     library whenever a new thread is created.  By setting a special
+     breakpoint at this location, GDB can detect when a new thread is
+     created.  We obtain this location via the td_ta_event_addr
+     call.  */
+  CORE_ADDR td_create_bp_addr;
 
-static td_err_e (*td_ta_new_p) (struct ps_prochandle * ps,
+  /* Location of the thread death event breakpoint.  */
+  CORE_ADDR td_death_bp_addr;
+
+  /* Pointers to the libthread_db functions.  */
+
+  td_err_e (*td_init_p) (void);
+
+  td_err_e (*td_ta_new_p) (struct ps_prochandle * ps,
 				td_thragent_t **ta);
-static td_err_e (*td_ta_map_id2thr_p) (const td_thragent_t *ta, thread_t pt,
-				       td_thrhandle_t *__th);
-static td_err_e (*td_ta_map_lwp2thr_p) (const td_thragent_t *ta,
-					lwpid_t lwpid, td_thrhandle_t *th);
-static td_err_e (*td_ta_thr_iter_p) (const td_thragent_t *ta,
-				     td_thr_iter_f *callback, void *cbdata_p,
-				     td_thr_state_e state, int ti_pri,
-				     sigset_t *ti_sigmask_p,
-				     unsigned int ti_user_flags);
-static td_err_e (*td_ta_event_addr_p) (const td_thragent_t *ta,
-				       td_event_e event, td_notify_t *ptr);
-static td_err_e (*td_ta_set_event_p) (const td_thragent_t *ta,
-				      td_thr_events_t *event);
-static td_err_e (*td_ta_event_getmsg_p) (const td_thragent_t *ta,
-					 td_event_msg_t *msg);
-
-static td_err_e (*td_thr_validate_p) (const td_thrhandle_t *th);
-static td_err_e (*td_thr_get_info_p) (const td_thrhandle_t *th,
-				      td_thrinfo_t *infop);
-static td_err_e (*td_thr_event_enable_p) (const td_thrhandle_t *th,
-					  int event);
-
-static td_err_e (*td_thr_tls_get_addr_p) (const td_thrhandle_t *th,
-					  void *map_address,
-					  size_t offset, void **address);
-
-/* Location of the thread creation event breakpoint.  The code at this
-   location in the child process will be called by the pthread library
-   whenever a new thread is created.  By setting a special breakpoint
-   at this location, GDB can detect when a new thread is created.  We
-   obtain this location via the td_ta_event_addr call.  */
-static CORE_ADDR td_create_bp_addr;
-
-/* Location of the thread death event breakpoint.  */
-static CORE_ADDR td_death_bp_addr;
+  td_err_e (*td_ta_map_id2thr_p) (const td_thragent_t *ta, thread_t pt,
+				  td_thrhandle_t *__th);
+  td_err_e (*td_ta_map_lwp2thr_p) (const td_thragent_t *ta,
+				   lwpid_t lwpid, td_thrhandle_t *th);
+  td_err_e (*td_ta_thr_iter_p) (const td_thragent_t *ta,
+				td_thr_iter_f *callback, void *cbdata_p,
+				td_thr_state_e state, int ti_pri,
+				sigset_t *ti_sigmask_p,
+				unsigned int ti_user_flags);
+  td_err_e (*td_ta_event_addr_p) (const td_thragent_t *ta,
+				  td_event_e event, td_notify_t *ptr);
+  td_err_e (*td_ta_set_event_p) (const td_thragent_t *ta,
+				 td_thr_events_t *event);
+  td_err_e (*td_ta_clear_event_p) (const td_thragent_t *ta,
+				   td_thr_events_t *event);
+  td_err_e (*td_ta_event_getmsg_p) (const td_thragent_t *ta,
+				    td_event_msg_t *msg);
+
+  td_err_e (*td_thr_validate_p) (const td_thrhandle_t *th);
+  td_err_e (*td_thr_get_info_p) (const td_thrhandle_t *th,
+				 td_thrinfo_t *infop);
+  td_err_e (*td_thr_event_enable_p) (const td_thrhandle_t *th,
+				     int event);
+
+  td_err_e (*td_thr_tls_get_addr_p) (const td_thrhandle_t *th,
+				     psaddr_t map_address,
+				     size_t offset, psaddr_t *address);
+};
 
-/* Prototypes for local functions.  */
-static void thread_db_find_new_threads (void);
-static void attach_thread (ptid_t ptid, const td_thrhandle_t *th_p,
-			   const td_thrinfo_t *ti_p, int verbose);
-static void detach_thread (ptid_t ptid, int verbose);
-
+/* List of known processes using thread_db, and the required
+   bookkeeping.  */
+struct thread_db_info *thread_db_list;
+
+static void thread_db_find_new_threads_1 (ptid_t ptid);
+static void thread_db_find_new_threads_2 (ptid_t ptid, int until_no_new);
+
+/* Add the current inferior to the list of processes using libpthread.
+   Return a pointer to the newly allocated object that was added to
+   THREAD_DB_LIST.  HANDLE is the handle returned by dlopen'ing
+   LIBTHREAD_DB_SO.  */
 
-/* Building process ids.  */
+static struct thread_db_info *
+add_thread_db_info (void *handle)
+{
+  struct thread_db_info *info;
+
+  info = xcalloc (1, sizeof (*info));
+  info->pid = ptid_get_pid (inferior_ptid);
+  info->handle = handle;
+  info->need_stale_parent_threads_check = 1;
+
+  info->next = thread_db_list;
+  thread_db_list = info;
+
+  return info;
+}
+
+/* Return the thread_db_info object representing the bookkeeping
+   related to process PID, if any; NULL otherwise.  */
 
-#define GET_PID(ptid)		ptid_get_pid (ptid)
-#define GET_LWP(ptid)		ptid_get_lwp (ptid)
-#define GET_THREAD(ptid)	ptid_get_tid (ptid)
+static struct thread_db_info *
+get_thread_db_info (int pid)
+{
+  struct thread_db_info *info;
 
-#define is_lwp(ptid)		(GET_LWP (ptid) != 0)
-#define is_thread(ptid)		(GET_THREAD (ptid) != 0)
+  for (info = thread_db_list; info; info = info->next)
+    if (pid == info->pid)
+      return info;
 
-#define BUILD_LWP(lwp, pid)	ptid_build (pid, lwp, 0)
+  return NULL;
+}
+
+/* When PID has exited or has been detached, we no longer want to keep
+   track of it as using libpthread.  Call this function to discard
+   thread_db related info related to PID.  Note that this closes
+   LIBTHREAD_DB_SO's dlopen'ed handle.  */
+
+static void
+delete_thread_db_info (int pid)
+{
+  struct thread_db_info *info, *info_prev;
+
+  info_prev = NULL;
+
+  for (info = thread_db_list; info; info_prev = info, info = info->next)
+    if (pid == info->pid)
+      break;
+
+  if (info == NULL)
+    return;
+
+  if (info->handle != NULL)
+    dlclose (info->handle);
+
+  if (info_prev)
+    info_prev->next = info->next;
+  else
+    thread_db_list = info->next;
+
+  xfree (info);
+}
+
+/* Prototypes for local functions.  */
+static int attach_thread (ptid_t ptid, const td_thrhandle_t *th_p,
+			  const td_thrinfo_t *ti_p);
+static void detach_thread (ptid_t ptid);
 
 
 /* Use "struct private_thread_info" to cache thread state.  This is
@@ -150,11 +245,8 @@ struct private_thread_info
   unsigned int dying:1;
 
   /* Cached thread state.  */
-  unsigned int th_valid:1;
-  unsigned int ti_valid:1;
-
   td_thrhandle_t th;
-  td_thrinfo_t ti;
+  thread_t tid;
 };
 
 
@@ -207,12 +299,51 @@ thread_db_err_str (td_err_e err)
       return "only part of register set was written/read";
     case TD_NOXREGS:
       return "X register set not available for this thread";
+#ifdef THREAD_DB_HAS_TD_NOTALLOC
+    case TD_NOTALLOC:
+      return "thread has not yet allocated TLS for given module";
+#endif
+#ifdef THREAD_DB_HAS_TD_VERSION
+    case TD_VERSION:
+      return "versions of libpthread and libthread_db do not match";
+#endif
+#ifdef THREAD_DB_HAS_TD_NOTLS
+    case TD_NOTLS:
+      return "there is no TLS segment in the given module";
+#endif
     default:
       snprintf (buf, sizeof (buf), "unknown thread_db error '%d'", err);
       return buf;
     }
 }
 
+/* Return 1 if any threads have been registered.  There may be none if
+   the threading library is not fully initialized yet.  */
+
+static int
+have_threads_callback (struct thread_info *thread, void *args)
+{
+  int pid = * (int *) args;
+  if (ptid_get_pid (thread->ptid) != pid)
+    return 0;
+
+  return thread->private != NULL;
+}
+
+static int
+have_threads (ptid_t ptid)
+{
+  int pid = ptid_get_pid (ptid);
+
+  return iterate_over_threads (have_threads_callback, &pid) != NULL;
+}
+
+struct thread_get_info_inout
+{
+  struct thread_info *thread_info;
+  struct thread_db_info *thread_db_info;
+};
+
 /* A callback function for td_ta_thr_iter, which we use to map all
    threads to LWPs.
 
@@ -224,79 +355,44 @@ thread_db_err_str (td_err_e err)
    zero is returned to indicate success.  */
 
 static int
-thread_get_info_callback (const td_thrhandle_t *thp, void *infop)
+thread_get_info_callback (const td_thrhandle_t *thp, void *argp)
 {
   td_thrinfo_t ti;
   td_err_e err;
-  struct thread_info *thread_info;
   ptid_t thread_ptid;
+  struct thread_get_info_inout *inout;
+  struct thread_db_info *info;
+
+  inout = argp;
+  info = inout->thread_db_info;
 
-  err = td_thr_get_info_p (thp, &ti);
+  err = info->td_thr_get_info_p (thp, &ti);
   if (err != TD_OK)
     error (_("thread_get_info_callback: cannot get thread info: %s"),
 	   thread_db_err_str (err));
 
   /* Fill the cache.  */
-  thread_ptid = ptid_build (GET_PID (inferior_ptid), ti.ti_lid, ti.ti_tid);
-  thread_info = find_thread_pid (thread_ptid);
+  thread_ptid = ptid_build (info->pid, ti.ti_lid, 0);
+  inout->thread_info = find_thread_ptid (thread_ptid);
 
   /* In the case of a zombie thread, don't continue.  We don't want to
      attach to it thinking it is a new thread.  */
   if (ti.ti_state == TD_THR_UNKNOWN || ti.ti_state == TD_THR_ZOMBIE)
-    {
-      if (infop != NULL)
-        *(struct thread_info **) infop = thread_info;
-      if (thread_info != NULL)
-	{
-	  memcpy (&thread_info->private->th, thp, sizeof (*thp));
-	  thread_info->private->th_valid = 1;
-	  memcpy (&thread_info->private->ti, &ti, sizeof (ti));
-	  thread_info->private->ti_valid = 1;
-	}
-      return TD_THR_ZOMBIE;
-    }
+    return TD_THR_ZOMBIE;
 
-  if (thread_info == NULL)
+  if (inout->thread_info == NULL)
     {
       /* New thread.  Attach to it now (why wait?).  */
-      attach_thread (thread_ptid, thp, &ti, 1);
-      thread_info = find_thread_pid (thread_ptid);
-      gdb_assert (thread_info != NULL);
+      if (!have_threads (thread_ptid))
+ 	thread_db_find_new_threads_1 (thread_ptid);
+      else
+	attach_thread (thread_ptid, thp, &ti);
+      inout->thread_info = find_thread_ptid (thread_ptid);
+      gdb_assert (inout->thread_info != NULL);
     }
 
-  memcpy (&thread_info->private->th, thp, sizeof (*thp));
-  thread_info->private->th_valid = 1;
-  memcpy (&thread_info->private->ti, &ti, sizeof (ti));
-  thread_info->private->ti_valid = 1;
-
-  if (infop != NULL)
-    *(struct thread_info **) infop = thread_info;
-
   return 0;
 }
-
-/* Accessor functions for the thread_db information, with caching.  */
-
-static void
-thread_db_map_id2thr (struct thread_info *thread_info, int fatal)
-{
-  td_err_e err;
-
-  if (thread_info->private->th_valid)
-    return;
-
-  err = td_ta_map_id2thr_p (thread_agent, GET_THREAD (thread_info->ptid),
-			    &thread_info->private->th);
-  if (err != TD_OK)
-    {
-      if (fatal)
-	error (_("Cannot find thread %ld: %s"),
-	       (long) GET_THREAD (thread_info->ptid),
-	       thread_db_err_str (err));
-    }
-  else
-    thread_info->private->th_valid = 1;
-}
 
 /* Convert between user-level thread ids and LWP ids.  */
 
@@ -305,21 +401,22 @@ thread_from_lwp (ptid_t ptid)
 {
   td_thrhandle_t th;
   td_err_e err;
-  struct thread_info *thread_info;
-  ptid_t thread_ptid;
+  struct thread_db_info *info;
+  struct thread_get_info_inout io = {0};
 
-  if (GET_LWP (ptid) == 0)
-    ptid = BUILD_LWP (GET_PID (ptid), GET_PID (ptid));
+  /* This ptid comes from linux-nat.c, which should always fill in the
+     LWP.  */
+  gdb_assert (GET_LWP (ptid) != 0);
 
-  gdb_assert (is_lwp (ptid));
+  info = get_thread_db_info (GET_PID (ptid));
 
-  err = td_ta_map_lwp2thr_p (thread_agent, GET_LWP (ptid), &th);
+  /* Access an lwp we know is stopped.  */
+  info->proc_handle.ptid = ptid;
+  err = info->td_ta_map_lwp2thr_p (info->thread_agent, GET_LWP (ptid), &th);
   if (err != TD_OK)
     error (_("Cannot find user-level thread for LWP %ld: %s"),
 	   GET_LWP (ptid), thread_db_err_str (err));
 
-  thread_info = NULL;
-
   /* Fetch the thread info.  If we get back TD_THR_ZOMBIE, then the
      event thread has already died.  If another gdb interface has called
      thread_alive() previously, the thread won't be found on the thread list
@@ -328,124 +425,98 @@ thread_from_lwp (ptid_t ptid)
      discovered thread id that we should add to the list.  Thus,
      we return a -1 ptid which is also how the thread list marks a
      dead thread.  */
-  if (thread_get_info_callback (&th, &thread_info) == TD_THR_ZOMBIE
-      && thread_info == NULL)
-    return pid_to_ptid (-1);
-
-  gdb_assert (thread_info && thread_info->private->ti_valid);
+  io.thread_db_info = info;
+  io.thread_info = NULL;
+  if (thread_get_info_callback (&th, &io) == TD_THR_ZOMBIE
+      && io.thread_info == NULL)
+    return minus_one_ptid;
 
-  return ptid_build (GET_PID (ptid), GET_LWP (ptid),
-		     thread_info->private->ti.ti_tid);
-}
-
-static ptid_t
-lwp_from_thread (ptid_t ptid)
-{
-  return BUILD_LWP (GET_LWP (ptid), GET_PID (ptid));
+  gdb_assert (ptid_get_tid (ptid) == 0);
+  return ptid;
 }
 
 
-void
-thread_db_init (struct target_ops *target)
-{
-  target_beneath = target;
-}
-
-static void *
-verbose_dlsym (void *handle, const char *name)
+/* Attach to lwp PTID, doing whatever else is required to have this
+   LWP under the debugger's control --- e.g., enabling event
+   reporting.  Returns true on success.  */
+int
+thread_db_attach_lwp (ptid_t ptid)
 {
-  void *sym = dlsym (handle, name);
-  if (sym == NULL)
-    warning (_("Symbol \"%s\" not found in libthread_db: %s"), name, dlerror ());
-  return sym;
-}
-
-static int
-thread_db_load (void)
-{
-  void *handle;
+  td_thrhandle_t th;
+  td_thrinfo_t ti;
   td_err_e err;
+  struct thread_db_info *info;
 
-  handle = dlopen (LIBTHREAD_DB_SO, RTLD_NOW);
-  if (handle == NULL)
-    {
-      fprintf_filtered (gdb_stderr, "\n\ndlopen failed on '%s' - %s\n",
-			LIBTHREAD_DB_SO, dlerror ());
-      fprintf_filtered (gdb_stderr,
-			"GDB will not be able to debug pthreads.\n\n");
-      return 0;
-    }
-
-  /* Initialize pointers to the dynamic library functions we will use.
-     Essential functions first.  */
-
-  td_init_p = verbose_dlsym (handle, "td_init");
-  if (td_init_p == NULL)
-    return 0;
-
-  td_ta_new_p = verbose_dlsym (handle, "td_ta_new");
-  if (td_ta_new_p == NULL)
-    return 0;
+  info = get_thread_db_info (GET_PID (ptid));
 
-  td_ta_map_id2thr_p = verbose_dlsym (handle, "td_ta_map_id2thr");
-  if (td_ta_map_id2thr_p == NULL)
+  if (info == NULL)
     return 0;
 
-  td_ta_map_lwp2thr_p = verbose_dlsym (handle, "td_ta_map_lwp2thr");
-  if (td_ta_map_lwp2thr_p == NULL)
-    return 0;
+  /* This ptid comes from linux-nat.c, which should always fill in the
+     LWP.  */
+  gdb_assert (GET_LWP (ptid) != 0);
 
-  td_ta_thr_iter_p = verbose_dlsym (handle, "td_ta_thr_iter");
-  if (td_ta_thr_iter_p == NULL)
-    return 0;
+  /* Access an lwp we know is stopped.  */
+  info->proc_handle.ptid = ptid;
 
-  td_thr_validate_p = verbose_dlsym (handle, "td_thr_validate");
-  if (td_thr_validate_p == NULL)
-    return 0;
+  /* If we have only looked at the first thread before libpthread was
+     initialized, we may not know its thread ID yet.  Make sure we do
+     before we add another thread to the list.  */
+  if (!have_threads (ptid))
+    thread_db_find_new_threads_1 (ptid);
 
-  td_thr_get_info_p = verbose_dlsym (handle, "td_thr_get_info");
-  if (td_thr_get_info_p == NULL)
+  err = info->td_ta_map_lwp2thr_p (info->thread_agent, GET_LWP (ptid), &th);
+  if (err != TD_OK)
+    /* Cannot find user-level thread.  */
     return 0;
 
-  /* Initialize the library.  */
-  err = td_init_p ();
+  err = info->td_thr_get_info_p (&th, &ti);
   if (err != TD_OK)
     {
-      warning (_("Cannot initialize libthread_db: %s"), thread_db_err_str (err));
+      warning (_("Cannot get thread info: %s"), thread_db_err_str (err));
       return 0;
     }
 
-  /* These are not essential.  */
-  td_ta_event_addr_p = dlsym (handle, "td_ta_event_addr");
-  td_ta_set_event_p = dlsym (handle, "td_ta_set_event");
-  td_ta_event_getmsg_p = dlsym (handle, "td_ta_event_getmsg");
-  td_thr_event_enable_p = dlsym (handle, "td_thr_event_enable");
-  td_thr_tls_get_addr_p = dlsym (handle, "td_thr_tls_get_addr");
-
+  attach_thread (ptid, &th, &ti);
   return 1;
 }
 
+static void *
+verbose_dlsym (void *handle, const char *name)
+{
+  void *sym = dlsym (handle, name);
+  if (sym == NULL)
+    warning (_("Symbol \"%s\" not found in libthread_db: %s"), name, dlerror ());
+  return sym;
+}
+
 static td_err_e
-enable_thread_event (td_thragent_t *thread_agent, int event, CORE_ADDR *bp)
+enable_thread_event (int event, CORE_ADDR *bp)
 {
   td_notify_t notify;
   td_err_e err;
+  struct thread_db_info *info;
+
+  info = get_thread_db_info (GET_PID (inferior_ptid));
+
+  /* Access an lwp we know is stopped.  */
+  info->proc_handle.ptid = inferior_ptid;
 
   /* Get the breakpoint address for thread EVENT.  */
-  err = td_ta_event_addr_p (thread_agent, event, &notify);
+  err = info->td_ta_event_addr_p (info->thread_agent, event, &notify);
   if (err != TD_OK)
     return err;
 
   /* Set up the breakpoint.  */
   gdb_assert (exec_bfd);
   (*bp) = (gdbarch_convert_from_func_ptr_addr
-	   (current_gdbarch,
+	   (target_gdbarch,
 	    /* Do proper sign extension for the target.  */
 	    (bfd_get_sign_extend_vma (exec_bfd) > 0
 	     ? (CORE_ADDR) (intptr_t) notify.u.bptaddr
 	     : (CORE_ADDR) (uintptr_t) notify.u.bptaddr),
 	    &current_target));
-  create_thread_event_breakpoint ((*bp));
+  create_thread_event_breakpoint (target_gdbarch, *bp);
 
   return TD_OK;
 }
@@ -454,17 +525,21 @@ static void
 enable_thread_event_reporting (void)
 {
   td_thr_events_t events;
-  td_notify_t notify;
   td_err_e err;
 #ifdef HAVE_GNU_LIBC_VERSION_H
   const char *libc_version;
   int libc_major, libc_minor;
 #endif
+  struct thread_db_info *info;
+
+  info = get_thread_db_info (GET_PID (inferior_ptid));
 
   /* We cannot use the thread event reporting facility if these
      functions aren't available.  */
-  if (td_ta_event_addr_p == NULL || td_ta_set_event_p == NULL
-      || td_ta_event_getmsg_p == NULL || td_thr_event_enable_p == NULL)
+  if (info->td_ta_event_addr_p == NULL
+      || info->td_ta_set_event_p == NULL
+      || info->td_ta_event_getmsg_p == NULL
+      || info->td_thr_event_enable_p == NULL)
     return;
 
   /* Set the process wide mask saying which events we're interested in.  */
@@ -472,16 +547,16 @@ enable_thread_event_reporting (void)
   td_event_addset (&events, TD_CREATE);
 
 #ifdef HAVE_GNU_LIBC_VERSION_H
-  /* FIXME: kettenis/2000-04-23: The event reporting facility is
-     broken for TD_DEATH events in glibc 2.1.3, so don't enable it for
-     now.  */
+  /* The event reporting facility is broken for TD_DEATH events in
+     glibc 2.1.3, so don't enable it if we have glibc but a lower
+     version.  */
   libc_version = gnu_get_libc_version ();
   if (sscanf (libc_version, "%d.%d", &libc_major, &libc_minor) == 2
       && (libc_major > 2 || (libc_major == 2 && libc_minor > 1)))
 #endif
     td_event_addset (&events, TD_DEATH);
 
-  err = td_ta_set_event_p (thread_agent, &events);
+  err = info->td_ta_set_event_p (info->thread_agent, &events);
   if (err != TD_OK)
     {
       warning (_("Unable to set global thread event mask: %s"),
@@ -491,11 +566,11 @@ enable_thread_event_reporting (void)
 
   /* Delete previous thread event breakpoints, if any.  */
   remove_thread_event_breakpoints ();
-  td_create_bp_addr = 0;
-  td_death_bp_addr = 0;
+  info->td_create_bp_addr = 0;
+  info->td_death_bp_addr = 0;
 
   /* Set up the thread creation event.  */
-  err = enable_thread_event (thread_agent, TD_CREATE, &td_create_bp_addr);
+  err = enable_thread_event (TD_CREATE, &info->td_create_bp_addr);
   if (err != TD_OK)
     {
       warning (_("Unable to get location for thread creation breakpoint: %s"),
@@ -504,7 +579,7 @@ enable_thread_event_reporting (void)
     }
 
   /* Set up the thread death event.  */
-  err = enable_thread_event (thread_agent, TD_DEATH, &td_death_bp_addr);
+  err = enable_thread_event (TD_DEATH, &info->td_death_bp_addr);
   if (err != TD_OK)
     {
       warning (_("Unable to get location for thread death breakpoint: %s"),
@@ -513,20 +588,337 @@ enable_thread_event_reporting (void)
     }
 }
 
+/* Same as thread_db_find_new_threads_1, but silently ignore errors.  */
+
 static void
-disable_thread_event_reporting (void)
+thread_db_find_new_threads_silently (ptid_t ptid)
 {
-  td_thr_events_t events;
+  volatile struct gdb_exception except;
 
-  /* Set the process wide mask saying we aren't interested in any
-     events anymore.  */
-  td_event_emptyset (&events);
-  td_ta_set_event_p (thread_agent, &events);
+  TRY_CATCH (except, RETURN_MASK_ERROR)
+    {
+      thread_db_find_new_threads_2 (ptid, 1);
+    }
 
-  /* Delete thread event breakpoints, if any.  */
-  remove_thread_event_breakpoints ();
-  td_create_bp_addr = 0;
-  td_death_bp_addr = 0;
+  if (except.reason < 0 && info_verbose)
+  {
+    exception_fprintf (gdb_stderr, except,
+                       "Warning: thread_db_find_new_threads_silently: ");
+  }
+}
+
+/* Lookup a library in which given symbol resides.
+   Note: this is looking in GDB process, not in the inferior.
+   Returns library name, or NULL.  */
+
+static const char *
+dladdr_to_soname (const void *addr)
+{
+  Dl_info info;
+
+  if (dladdr (addr, &info) != 0)
+    return info.dli_fname;
+  return NULL;
+}
+
+/* Attempt to initialize dlopen()ed libthread_db, described by HANDLE.
+   Return 1 on success.
+   Failure could happen if libthread_db does not have symbols we expect,
+   or when it refuses to work with the current inferior (e.g. due to
+   version mismatch between libthread_db and libpthread).  */
+
+static int
+try_thread_db_load_1 (struct thread_db_info *info)
+{
+  td_err_e err;
+
+  /* Initialize pointers to the dynamic library functions we will use.
+     Essential functions first.  */
+
+  info->td_init_p = verbose_dlsym (info->handle, "td_init");
+  if (info->td_init_p == NULL)
+    return 0;
+
+  err = info->td_init_p ();
+  if (err != TD_OK)
+    {
+      warning (_("Cannot initialize libthread_db: %s"), thread_db_err_str (err));
+      return 0;
+    }
+
+  info->td_ta_new_p = verbose_dlsym (info->handle, "td_ta_new");
+  if (info->td_ta_new_p == NULL)
+    return 0;
+
+  /* Initialize the structure that identifies the child process.  */
+  info->proc_handle.ptid = inferior_ptid;
+
+  /* Now attempt to open a connection to the thread library.  */
+  err = info->td_ta_new_p (&info->proc_handle, &info->thread_agent);
+  if (err != TD_OK)
+    {
+      if (info_verbose)
+	printf_unfiltered (_("td_ta_new failed: %s\n"),
+			   thread_db_err_str (err));
+      else
+        switch (err)
+          {
+            case TD_NOLIBTHREAD:
+#ifdef THREAD_DB_HAS_TD_VERSION
+            case TD_VERSION:
+#endif
+              /* The errors above are not unexpected and silently ignored:
+                 they just mean we haven't found correct version of
+                 libthread_db yet.  */
+              break;
+            default:
+              warning (_("td_ta_new failed: %s"), thread_db_err_str (err));
+          }
+      return 0;
+    }
+
+  info->td_ta_map_id2thr_p = verbose_dlsym (info->handle, "td_ta_map_id2thr");
+  if (info->td_ta_map_id2thr_p == NULL)
+    return 0;
+
+  info->td_ta_map_lwp2thr_p = verbose_dlsym (info->handle, "td_ta_map_lwp2thr");
+  if (info->td_ta_map_lwp2thr_p == NULL)
+    return 0;
+
+  info->td_ta_thr_iter_p = verbose_dlsym (info->handle, "td_ta_thr_iter");
+  if (info->td_ta_thr_iter_p == NULL)
+    return 0;
+
+  info->td_thr_validate_p = verbose_dlsym (info->handle, "td_thr_validate");
+  if (info->td_thr_validate_p == NULL)
+    return 0;
+
+  info->td_thr_get_info_p = verbose_dlsym (info->handle, "td_thr_get_info");
+  if (info->td_thr_get_info_p == NULL)
+    return 0;
+
+  /* These are not essential.  */
+  info->td_ta_event_addr_p = dlsym (info->handle, "td_ta_event_addr");
+  info->td_ta_set_event_p = dlsym (info->handle, "td_ta_set_event");
+  info->td_ta_clear_event_p = dlsym (info->handle, "td_ta_clear_event");
+  info->td_ta_event_getmsg_p = dlsym (info->handle, "td_ta_event_getmsg");
+  info->td_thr_event_enable_p = dlsym (info->handle, "td_thr_event_enable");
+  info->td_thr_tls_get_addr_p = dlsym (info->handle, "td_thr_tls_get_addr");
+
+  printf_unfiltered (_("[Thread debugging using libthread_db enabled]\n"));
+
+  if (info_verbose || *libthread_db_search_path)
+    {
+      const char *library;
+
+      library = dladdr_to_soname (*info->td_ta_new_p);
+      if (library == NULL)
+	library = LIBTHREAD_DB_SO;
+
+      printf_unfiltered (_("Using host libthread_db library \"%s\".\n"),
+			 library);
+    }
+
+  /* The thread library was detected.  Activate the thread_db target
+     if this is the first process using it.  */
+  if (thread_db_list->next == NULL)
+    push_target (&thread_db_ops);
+
+  enable_thread_event_reporting ();
+
+  /* There appears to be a bug in glibc-2.3.6: calls to td_thr_get_info fail
+     with TD_ERR for statically linked executables if td_thr_get_info is
+     called before glibc has initialized itself.  Silently ignore such
+     errors, and let gdb enumerate threads again later.  */
+  thread_db_find_new_threads_silently (inferior_ptid);
+
+  return 1;
+}
+
+/* Attempt to use LIBRARY as libthread_db.  LIBRARY could be absolute,
+   relative, or just LIBTHREAD_DB.  */
+
+static int
+try_thread_db_load (const char *library)
+{
+  void *handle;
+  struct thread_db_info *info;
+
+  if (info_verbose)
+    printf_unfiltered (_("Trying host libthread_db library: %s.\n"),
+                       library);
+  handle = dlopen (library, RTLD_NOW);
+  if (handle == NULL)
+    {
+      if (info_verbose)
+	printf_unfiltered (_("dlopen failed: %s.\n"), dlerror ());
+      return 0;
+    }
+
+  if (info_verbose && strchr (library, '/') == NULL)
+    {
+      void *td_init;
+
+      td_init = dlsym (handle, "td_init");
+      if (td_init != NULL)
+        {
+          const char *const libpath = dladdr_to_soname (td_init);
+
+          if (libpath != NULL)
+            printf_unfiltered (_("Host %s resolved to: %s.\n"),
+                               library, libpath);
+        }
+    }
+
+  info = add_thread_db_info (handle);
+
+  if (try_thread_db_load_1 (info))
+    return 1;
+
+  /* This library "refused" to work on current inferior.  */
+  delete_thread_db_info (GET_PID (inferior_ptid));
+  return 0;
+}
+
+
+/* Search libthread_db_search_path for libthread_db which "agrees"
+   to work on current inferior.  */
+
+static int
+thread_db_load_search (void)
+{
+  char path[PATH_MAX];
+  const char *search_path = libthread_db_search_path;
+  int rc = 0;
+
+  while (*search_path)
+    {
+      const char *end = strchr (search_path, ':');
+      if (end)
+	{
+	  size_t len = end - search_path;
+          if (len + 1 + strlen (LIBTHREAD_DB_SO) + 1 > sizeof (path))
+            {
+              char *cp = xmalloc (len + 1);
+              memcpy (cp, search_path, len);
+              cp[len] = '\0';
+              warning (_("libthread_db_search_path component too long,"
+                         " ignored: %s."), cp);
+              xfree (cp);
+              search_path += len + 1;
+              continue;
+            }
+	  memcpy (path, search_path, len);
+	  path[len] = '\0';
+	  search_path += len + 1;
+	}
+      else
+	{
+          size_t len = strlen (search_path);
+
+          if (len + 1 + strlen (LIBTHREAD_DB_SO) + 1 > sizeof (path))
+            {
+              warning (_("libthread_db_search_path component too long,"
+                         " ignored: %s."), search_path);
+              break;
+            }
+	  memcpy (path, search_path, len + 1);
+	  search_path += len;
+	}
+      strcat (path, "/");
+      strcat (path, LIBTHREAD_DB_SO);
+      if (try_thread_db_load (path))
+	{
+	  rc = 1;
+	  break;
+	}
+    }
+  if (rc == 0)
+    rc = try_thread_db_load (LIBTHREAD_DB_SO);
+  return rc;
+}
+
+/* Attempt to load and initialize libthread_db.
+   Return 1 on success.
+ */
+
+static int
+thread_db_load (void)
+{
+  struct objfile *obj;
+  struct thread_db_info *info;
+
+  info = get_thread_db_info (GET_PID (inferior_ptid));
+
+  if (info != NULL)
+    return 1;
+
+  /* Don't attempt to use thread_db on targets which can not run
+     (executables not running yet, core files) for now.  */
+  if (!target_has_execution)
+    return 0;
+
+  /* Don't attempt to use thread_db for remote targets.  */
+  if (!target_can_run (&current_target))
+    return 0;
+
+  if (thread_db_load_search ())
+    return 1;
+
+  /* None of the libthread_db's on our search path, not the system default
+     ones worked.  If the executable is dynamically linked against
+     libpthread, try loading libthread_db from the same directory.  */
+
+  ALL_OBJFILES (obj)
+    if (libpthread_name_p (obj->name))
+      {
+	char path[PATH_MAX], *cp;
+
+	gdb_assert (strlen (obj->name) < sizeof (path));
+	strcpy (path, obj->name);
+	cp = strrchr (path, '/');
+
+	if (cp == NULL)
+	  {
+	    warning (_("Expected absolute pathname for libpthread in the"
+		       " inferior, but got %s."), path);
+	  }
+	else if (cp + 1 + strlen (LIBTHREAD_DB_SO) + 1 > path + sizeof (path))
+	  {
+	    warning (_("Unexpected: path to libpthread in the inferior is"
+		       " too long: %s"), path);
+	  }
+	else
+	  {
+	    strcpy (cp + 1, LIBTHREAD_DB_SO);
+	    if (try_thread_db_load (path))
+	      return 1;
+	  }
+	warning (_("Unable to find libthread_db matching inferior's thread"
+		   " library, thread debugging will not be available."));
+	return 0;
+    }
+  /* Either this executable isn't using libpthread at all, or it is
+     statically linked.  Since we can't easily distinguish these two cases,
+     no warning is issued.  */
+  return 0;
+}
+
+static void
+disable_thread_event_reporting (struct thread_db_info *info)
+{
+  if (info->td_ta_clear_event_p != NULL)
+    {
+      td_thr_events_t events;
+
+      /* Set the process wide mask saying we aren't interested in any
+	 events anymore.  */
+      td_event_fillset (&events);
+      info->td_ta_clear_event_p (info->thread_agent, &events);
+    }
+
+  info->td_create_bp_addr = 0;
+  info->td_death_bp_addr = 0;
 }
 
 static void
@@ -564,90 +956,33 @@ check_thread_signals (void)
 void
 check_for_thread_db (void)
 {
-  td_err_e err;
-  static int already_loaded;
-
-  /* First time through, report that libthread_db was successfuly
-     loaded.  Can't print this in in thread_db_load as, at that stage,
-     the interpreter and it's console haven't started.  */
-
-  if (!already_loaded)
-    {
-      Dl_info info;
-      const char *library = NULL;
-      if (dladdr ((*td_ta_new_p), &info) != 0)
-	library = info.dli_fname;
-
-      /* Try dlinfo?  */
-
-      if (library == NULL)
-	/* Paranoid - don't let a NULL path slip through.  */
-	library = LIBTHREAD_DB_SO;
-
-      printf_unfiltered (_("Using host libthread_db library \"%s\".\n"),
-			 library);
-      already_loaded = 1;
-    }
-
-  if (using_thread_db)
-    /* Nothing to do.  The thread library was already detected and the
-       target vector was already activated.  */
+  /* Do nothing if we couldn't load libthread_db.so.1.  */
+  if (!thread_db_load ())
     return;
-
-  /* Don't attempt to use thread_db on targets which can not run
-     (executables not running yet, core files) for now.  */
-  if (!target_has_execution)
-    return;
-
-  /* Initialize the structure that identifies the child process.  */
-  proc_handle.pid = GET_PID (inferior_ptid);
-
-  /* Now attempt to open a connection to the thread library.  */
-  err = td_ta_new_p (&proc_handle, &thread_agent);
-  switch (err)
-    {
-    case TD_NOLIBTHREAD:
-      /* No thread library was detected.  */
-      break;
-
-    case TD_OK:
-      printf_unfiltered (_("[Thread debugging using libthread_db enabled]\n"));
-
-      /* The thread library was detected.  Activate the thread_db target.  */
-      push_target (&thread_db_ops);
-      using_thread_db = 1;
-
-      enable_thread_event_reporting ();
-      thread_db_find_new_threads ();
-      break;
-
-    default:
-      warning (_("Cannot initialize thread debugging library: %s"),
-	       thread_db_err_str (err));
-      break;
-    }
 }
 
 static void
 thread_db_new_objfile (struct objfile *objfile)
 {
+  /* This observer must always be called with inferior_ptid set
+     correctly.  */
+
   if (objfile != NULL)
     check_for_thread_db ();
-
-  if (target_new_objfile_chain)
-    target_new_objfile_chain (objfile);
 }
 
 /* Attach to a new thread.  This function is called when we receive a
    TD_CREATE event or when we iterate over all threads and find one
-   that wasn't already in our list.  */
+   that wasn't already in our list.  Returns true on success.  */
 
-static void
+static int
 attach_thread (ptid_t ptid, const td_thrhandle_t *th_p,
-	       const td_thrinfo_t *ti_p, int verbose)
+	       const td_thrinfo_t *ti_p)
 {
-  struct thread_info *tp;
+  struct private_thread_info *private;
+  struct thread_info *tp = NULL;
   td_err_e err;
+  struct thread_db_info *info;
 
   /* If we're being called after a TD_CREATE event, we may already
      know about this thread.  There are two ways this can happen.  We
@@ -661,122 +996,113 @@ attach_thread (ptid_t ptid, const td_thrhandle_t *th_p,
      thread and attach to the new one.  */
   if (in_thread_list (ptid))
     {
-      tp = find_thread_pid (ptid);
+      tp = find_thread_ptid (ptid);
       gdb_assert (tp != NULL);
 
-      if (!tp->private->dying)
-        return;
+      /* If tp->private is NULL, then GDB is already attached to this
+	 thread, but we do not know anything about it.  We can learn
+	 about it here.  This can only happen if we have some other
+	 way besides libthread_db to notice new threads (i.e.
+	 PTRACE_EVENT_CLONE); assume the same mechanism notices thread
+	 exit, so this can not be a stale thread recreated with the
+	 same ID.  */
+      if (tp->private != NULL)
+	{
+	  if (!tp->private->dying)
+	    return 0;
 
-      delete_thread (ptid);
+	  delete_thread (ptid);
+	  tp = NULL;
+	}
     }
 
   check_thread_signals ();
 
-  /* Add the thread to GDB's thread list.  */
-  tp = add_thread (ptid);
-  tp->private = xmalloc (sizeof (struct private_thread_info));
-  memset (tp->private, 0, sizeof (struct private_thread_info));
-
-  if (verbose)
-    printf_unfiltered (_("[New %s]\n"), target_pid_to_str (ptid));
-
   if (ti_p->ti_state == TD_THR_UNKNOWN || ti_p->ti_state == TD_THR_ZOMBIE)
-    return;			/* A zombie thread -- do not attach.  */
+    return 0;			/* A zombie thread -- do not attach.  */
 
   /* Under GNU/Linux, we have to attach to each and every thread.  */
-#ifdef ATTACH_LWP
-  ATTACH_LWP (BUILD_LWP (ti_p->ti_lid, GET_PID (ptid)), 0);
-#endif
+  if (tp == NULL
+      && lin_lwp_attach_lwp (BUILD_LWP (ti_p->ti_lid, GET_PID (ptid))) < 0)
+    return 0;
 
-  /* Enable thread event reporting for this thread.  */
-  err = td_thr_event_enable_p (th_p, 1);
-  if (err != TD_OK)
-    error (_("Cannot enable thread event reporting for %s: %s"),
-	   target_pid_to_str (ptid), thread_db_err_str (err));
-}
+  /* Construct the thread's private data.  */
+  private = xmalloc (sizeof (struct private_thread_info));
+  memset (private, 0, sizeof (struct private_thread_info));
 
-static void
-thread_db_attach (char *args, int from_tty)
-{
-  target_beneath->to_attach (args, from_tty);
+  /* A thread ID of zero may mean the thread library has not initialized
+     yet.  But we shouldn't even get here if that's the case.  FIXME:
+     if we change GDB to always have at least one thread in the thread
+     list this will have to go somewhere else; maybe private == NULL
+     until the thread_db target claims it.  */
+  gdb_assert (ti_p->ti_tid != 0);
+  private->th = *th_p;
+  private->tid = ti_p->ti_tid;
 
-  /* Destroy thread info; it's no longer valid.  */
-  init_thread_list ();
+  /* Add the thread to GDB's thread list.  */
+  if (tp == NULL)
+    tp = add_thread_with_info (ptid, private);
+  else
+    tp->private = private;
 
-  /* The child process is now the actual multi-threaded
-     program.  Snatch its process ID...  */
-  proc_handle.pid = GET_PID (inferior_ptid);
+  info = get_thread_db_info (GET_PID (ptid));
 
-  /* ...and perform the remaining initialization steps.  */
-  enable_thread_event_reporting ();
-  thread_db_find_new_threads ();
+  /* Enable thread event reporting for this thread.  */
+  err = info->td_thr_event_enable_p (th_p, 1);
+  if (err != TD_OK)
+    error (_("Cannot enable thread event reporting for %s: %s"),
+	   target_pid_to_str (ptid), thread_db_err_str (err));
+  return 1;
 }
 
 static void
-detach_thread (ptid_t ptid, int verbose)
+detach_thread (ptid_t ptid)
 {
   struct thread_info *thread_info;
 
-  if (verbose)
-    printf_unfiltered (_("[%s exited]\n"), target_pid_to_str (ptid));
-
   /* Don't delete the thread now, because it still reports as active
      until it has executed a few instructions after the event
      breakpoint - if we deleted it now, "info threads" would cause us
      to re-attach to it.  Just mark it as having had a TD_DEATH
      event.  This means that we won't delete it from our thread list
      until we notice that it's dead (via prune_threads), or until
-     something re-uses its thread ID.  */
-  thread_info = find_thread_pid (ptid);
-  gdb_assert (thread_info != NULL);
+     something re-uses its thread ID.  We'll report the thread exit
+     when the underlying LWP dies.  */
+  thread_info = find_thread_ptid (ptid);
+  gdb_assert (thread_info != NULL && thread_info->private != NULL);
   thread_info->private->dying = 1;
 }
 
 static void
-thread_db_detach (char *args, int from_tty)
+thread_db_detach (struct target_ops *ops, char *args, int from_tty)
 {
-  disable_thread_event_reporting ();
-
-  /* There's no need to save & restore inferior_ptid here, since the
-     inferior is supposed to be survive this function call.  */
-  inferior_ptid = lwp_from_thread (inferior_ptid);
-
-  /* Forget about the child's process ID.  We shouldn't need it
-     anymore.  */
-  proc_handle.pid = 0;
-
-  target_beneath->to_detach (args, from_tty);
-}
+  struct target_ops *target_beneath = find_target_beneath (ops);
+  struct thread_db_info *info;
 
-static int
-clear_lwpid_callback (struct thread_info *thread, void *dummy)
-{
-  /* If we know that our thread implementation is 1-to-1, we could save
-     a certain amount of information; it's not clear how much, so we
-     are always conservative.  */
+  info = get_thread_db_info (GET_PID (inferior_ptid));
 
-  thread->private->th_valid = 0;
-  thread->private->ti_valid = 0;
+  if (info)
+    {
+      disable_thread_event_reporting (info);
 
-  return 0;
-}
+      /* Delete the old thread event breakpoints.  Note that unlike
+	 when mourning, we can remove them here because there's still
+	 a live inferior to poke at.  In any case, GDB will not try to
+	 insert anything in the inferior when removing a
+	 breakpoint.  */
+      remove_thread_event_breakpoints ();
 
-static void
-thread_db_resume (ptid_t ptid, int step, enum target_signal signo)
-{
-  struct cleanup *old_chain = save_inferior_ptid ();
-
-  if (GET_PID (ptid) == -1)
-    inferior_ptid = lwp_from_thread (inferior_ptid);
-  else if (is_thread (ptid))
-    ptid = lwp_from_thread (ptid);
+      delete_thread_db_info (GET_PID (inferior_ptid));
+    }
 
-  /* Clear cached data which may not be valid after the resume.  */
-  iterate_over_threads (clear_lwpid_callback, NULL);
+  target_beneath->to_detach (target_beneath, args, from_tty);
 
-  target_beneath->to_resume (ptid, step, signo);
+  /* NOTE: From this point on, inferior_ptid is null_ptid.  */
 
-  do_cleanups (old_chain);
+  /* If there are no more processes using libpthread, detach the
+     thread_db target ops.  */
+  if (!thread_db_list)
+    unpush_target (&thread_db_ops);
 }
 
 /* Check if PID is currently stopped at the location of a thread event
@@ -786,17 +1112,33 @@ thread_db_resume (ptid_t ptid, int step, enum target_signal signo)
 static void
 check_event (ptid_t ptid)
 {
+  struct regcache *regcache = get_thread_regcache (ptid);
+  struct gdbarch *gdbarch = get_regcache_arch (regcache);
   td_event_msg_t msg;
   td_thrinfo_t ti;
   td_err_e err;
   CORE_ADDR stop_pc;
   int loop = 0;
+  struct thread_db_info *info;
+
+  info = get_thread_db_info (GET_PID (ptid));
 
   /* Bail out early if we're not at a thread event breakpoint.  */
-  stop_pc = read_pc_pid (ptid) - DECR_PC_AFTER_BREAK;
-  if (stop_pc != td_create_bp_addr && stop_pc != td_death_bp_addr)
+  stop_pc = regcache_read_pc (regcache)
+	    - gdbarch_decr_pc_after_break (gdbarch);
+  if (stop_pc != info->td_create_bp_addr
+      && stop_pc != info->td_death_bp_addr)
     return;
 
+  /* Access an lwp we know is stopped.  */
+  info->proc_handle.ptid = ptid;
+
+  /* If we have only looked at the first thread before libpthread was
+     initialized, we may not know its thread ID yet.  Make sure we do
+     before we add another thread to the list.  */
+  if (!have_threads (ptid))
+    thread_db_find_new_threads_1 (ptid);
+
   /* If we are at a create breakpoint, we do not know what new lwp
      was created and cannot specifically locate the event message for it.
      We have to call td_ta_event_getmsg() to get
@@ -815,7 +1157,7 @@ check_event (ptid_t ptid)
 
   do
     {
-      err = td_ta_event_getmsg_p (thread_agent, &msg);
+      err = info->td_ta_event_getmsg_p (info->thread_agent, &msg);
       if (err != TD_OK)
 	{
 	  if (err == TD_NOMSG)
@@ -825,18 +1167,18 @@ check_event (ptid_t ptid)
 		 thread_db_err_str (err));
 	}
 
-      err = td_thr_get_info_p (msg.th_p, &ti);
+      err = info->td_thr_get_info_p (msg.th_p, &ti);
       if (err != TD_OK)
 	error (_("Cannot get thread info: %s"), thread_db_err_str (err));
 
-      ptid = ptid_build (GET_PID (ptid), ti.ti_lid, ti.ti_tid);
+      ptid = ptid_build (GET_PID (ptid), ti.ti_lid, 0);
 
       switch (msg.event)
 	{
 	case TD_CREATE:
 	  /* Call attach_thread whether or not we already know about a
 	     thread with this thread ID.  */
-	  attach_thread (ptid, msg.th_p, &ti, 1);
+	  attach_thread (ptid, msg.th_p, &ti);
 
 	  break;
 
@@ -845,7 +1187,7 @@ check_event (ptid_t ptid)
 	  if (!in_thread_list (ptid))
 	    error (_("Spurious thread death event."));
 
-	  detach_thread (ptid, 1);
+	  detach_thread (ptid);
 
 	  break;
 
@@ -857,128 +1199,103 @@ check_event (ptid_t ptid)
 }
 
 static ptid_t
-thread_db_wait (ptid_t ptid, struct target_waitstatus *ourstatus)
+thread_db_wait (struct target_ops *ops,
+		ptid_t ptid, struct target_waitstatus *ourstatus,
+		int options)
 {
-  extern ptid_t trap_ptid;
-
-  if (GET_PID (ptid) != -1 && is_thread (ptid))
-    ptid = lwp_from_thread (ptid);
+  struct thread_db_info *info;
+  struct target_ops *beneath = find_target_beneath (ops);
 
-  ptid = target_beneath->to_wait (ptid, ourstatus);
+  ptid = beneath->to_wait (beneath, ptid, ourstatus, options);
 
-  if (proc_handle.pid == 0)
-    /* The current child process isn't the actual multi-threaded
-       program yet, so don't try to do any special thread-specific
-       post-processing and bail out early.  */
+  if (ourstatus->kind == TARGET_WAITKIND_IGNORE)
     return ptid;
 
-  if (ourstatus->kind == TARGET_WAITKIND_EXITED)
-    return pid_to_ptid (-1);
-
-  if (ourstatus->kind == TARGET_WAITKIND_STOPPED
-      && ourstatus->value.sig == TARGET_SIGNAL_TRAP)
-    /* Check for a thread event.  */
-    check_event (ptid);
+  if (ourstatus->kind == TARGET_WAITKIND_EXITED
+      || ourstatus->kind == TARGET_WAITKIND_SIGNALLED)
+    return ptid;
 
-  if (!ptid_equal (trap_ptid, null_ptid))
-    trap_ptid = thread_from_lwp (trap_ptid);
-
-  /* Change the ptid back into the higher level PID + TID format.
-     If the thread is dead and no longer on the thread list, we will 
-     get back a dead ptid.  This can occur if the thread death event
-     gets postponed by other simultaneous events.  In such a case, 
-     we want to just ignore the event and continue on.  */
-  ptid = thread_from_lwp (ptid);
-  if (GET_PID (ptid) == -1)
-    ourstatus->kind = TARGET_WAITKIND_SPURIOUS;
-  
-  return ptid;
-}
+  info = get_thread_db_info (GET_PID (ptid));
 
-static LONGEST
-thread_db_xfer_partial (struct target_ops *ops, enum target_object object,
-			const char *annex, gdb_byte *readbuf,
-			const gdb_byte *writebuf, ULONGEST offset, LONGEST len)
-{
-  struct cleanup *old_chain = save_inferior_ptid ();
-  LONGEST xfer;
+  /* If this process isn't using thread_db, we're done.  */
+  if (info == NULL)
+    return ptid;
 
-  if (is_thread (inferior_ptid))
+  if (ourstatus->kind == TARGET_WAITKIND_EXECD)
     {
-      /* FIXME: This seems to be necessary to make sure breakpoints
-         are removed.  */
-      if (!target_thread_alive (inferior_ptid))
-	inferior_ptid = pid_to_ptid (GET_PID (inferior_ptid));
-      else
-	inferior_ptid = lwp_from_thread (inferior_ptid);
-    }
+      /* New image, it may or may not end up using thread_db.  Assume
+	 not unless we find otherwise.  */
+      delete_thread_db_info (GET_PID (ptid));
+      if (!thread_db_list)
+ 	unpush_target (&thread_db_ops);
 
-  xfer = target_beneath->to_xfer_partial (ops, object, annex,
-					  readbuf, writebuf, offset, len);
+      /* Thread event breakpoints are deleted by
+	 update_breakpoints_after_exec.  */
 
-  do_cleanups (old_chain);
-  return xfer;
-}
+      return ptid;
+    }
 
-static void
-thread_db_kill (void)
-{
-  /* There's no need to save & restore inferior_ptid here, since the
-     inferior isn't supposed to survive this function call.  */
-  inferior_ptid = lwp_from_thread (inferior_ptid);
-  target_beneath->to_kill ();
-}
+  /* If we do not know about the main thread yet, this would be a good time to
+     find it.  */
+  if (ourstatus->kind == TARGET_WAITKIND_STOPPED && !have_threads (ptid))
+    thread_db_find_new_threads_1 (ptid);
 
-static void
-thread_db_create_inferior (char *exec_file, char *allargs, char **env,
-			   int from_tty)
-{
-  unpush_target (&thread_db_ops);
-  using_thread_db = 0;
-  target_beneath->to_create_inferior (exec_file, allargs, env, from_tty);
-}
+  if (ourstatus->kind == TARGET_WAITKIND_STOPPED
+      && ourstatus->value.sig == TARGET_SIGNAL_TRAP)
+    /* Check for a thread event.  */
+    check_event (ptid);
 
-static void
-thread_db_post_startup_inferior (ptid_t ptid)
-{
-  if (proc_handle.pid == 0)
+  if (have_threads (ptid))
     {
-      /* The child process is now the actual multi-threaded
-         program.  Snatch its process ID...  */
-      proc_handle.pid = GET_PID (ptid);
-
-      /* ...and perform the remaining initialization steps.  */
-      enable_thread_event_reporting ();
-      thread_db_find_new_threads ();
+      /* Change ptids back into the higher level PID + TID format.  If
+	 the thread is dead and no longer on the thread list, we will
+	 get back a dead ptid.  This can occur if the thread death
+	 event gets postponed by other simultaneous events.  In such a
+	 case, we want to just ignore the event and continue on.  */
+
+      ptid = thread_from_lwp (ptid);
+      if (GET_PID (ptid) == -1)
+	ourstatus->kind = TARGET_WAITKIND_SPURIOUS;
     }
+
+  return ptid;
 }
 
 static void
-thread_db_mourn_inferior (void)
+thread_db_mourn_inferior (struct target_ops *ops)
 {
-  /* Forget about the child's process ID.  We shouldn't need it
-     anymore.  */
-  proc_handle.pid = 0;
+  struct target_ops *target_beneath = find_target_beneath (ops);
 
-  target_beneath->to_mourn_inferior ();
+  delete_thread_db_info (GET_PID (inferior_ptid));
+
+  target_beneath->to_mourn_inferior (target_beneath);
 
   /* Delete the old thread event breakpoints.  Do this after mourning
      the inferior, so that we don't try to uninsert them.  */
   remove_thread_event_breakpoints ();
 
   /* Detach thread_db target ops.  */
-  unpush_target (&thread_db_ops);
-  using_thread_db = 0;
+  if (!thread_db_list)
+    unpush_target (ops);
 }
 
+struct callback_data
+{
+  struct thread_db_info *info;
+  int new_threads;
+};
+
 static int
 find_new_threads_callback (const td_thrhandle_t *th_p, void *data)
 {
   td_thrinfo_t ti;
   td_err_e err;
   ptid_t ptid;
+  struct thread_info *tp;
+  struct callback_data *cb_data = data;
+  struct thread_db_info *info = cb_data->info;
 
-  err = td_thr_get_info_p (th_p, &ti);
+  err = info->td_thr_get_info_p (th_p, &ti);
   if (err != TD_OK)
     error (_("find_new_threads_callback: cannot get thread info: %s"),
 	   thread_db_err_str (err));
@@ -986,48 +1303,193 @@ find_new_threads_callback (const td_thrhandle_t *th_p, void *data)
   if (ti.ti_state == TD_THR_UNKNOWN || ti.ti_state == TD_THR_ZOMBIE)
     return 0;			/* A zombie -- ignore.  */
 
-  ptid = ptid_build (GET_PID (inferior_ptid), ti.ti_lid, ti.ti_tid);
+  if (ti.ti_tid == 0)
+    {
+      /* A thread ID of zero means that this is the main thread, but
+	 glibc has not yet initialized thread-local storage and the
+	 pthread library.  We do not know what the thread's TID will
+	 be yet.  Just enable event reporting and otherwise ignore
+	 it.  */
+
+      /* In that case, we're not stopped in a fork syscall and don't
+	 need this glibc bug workaround.  */
+      info->need_stale_parent_threads_check = 0;
+
+      err = info->td_thr_event_enable_p (th_p, 1);
+      if (err != TD_OK)
+	error (_("Cannot enable thread event reporting for LWP %d: %s"),
+	       (int) ti.ti_lid, thread_db_err_str (err));
 
-  if (!in_thread_list (ptid))
-    attach_thread (ptid, th_p, &ti, 1);
+      return 0;
+    }
+
+  /* Ignore stale parent threads, caused by glibc/BZ5983.  This is a
+     bit expensive, as it needs to open /proc/pid/status, so try to
+     avoid doing the work if we know we don't have to.  */
+  if (info->need_stale_parent_threads_check)
+    {
+      int tgid = linux_proc_get_tgid (ti.ti_lid);
+      if (tgid != -1 && tgid != info->pid)
+	return 0;
+    }
+
+  ptid = ptid_build (info->pid, ti.ti_lid, 0);
+  tp = find_thread_ptid (ptid);
+  if (tp == NULL || tp->private == NULL)
+    {
+      if (attach_thread (ptid, th_p, &ti))
+	cb_data->new_threads += 1;
+      else
+	/* Problem attaching this thread; perhaps it exited before we
+	   could attach it?
+	   This could mean that the thread list inside glibc itself is in
+	   inconsistent state, and libthread_db could go on looping forever
+	   (observed with glibc-2.3.6).  To prevent that, terminate
+	   iteration: thread_db_find_new_threads_2 will retry.  */
+	return 1;
+    }
 
   return 0;
 }
 
+/* Helper for thread_db_find_new_threads_2.
+   Returns number of new threads found.  */
+
+static int
+find_new_threads_once (struct thread_db_info *info, int iteration,
+		       td_err_e *errp)
+{
+  volatile struct gdb_exception except;
+  struct callback_data data;
+  td_err_e err = TD_ERR;
+
+  data.info = info;
+  data.new_threads = 0;
+
+  TRY_CATCH (except, RETURN_MASK_ERROR)
+    {
+      /* Iterate over all user-space threads to discover new threads.  */
+      err = info->td_ta_thr_iter_p (info->thread_agent,
+				    find_new_threads_callback,
+				    &data,
+				    TD_THR_ANY_STATE,
+				    TD_THR_LOWEST_PRIORITY,
+				    TD_SIGNO_MASK,
+				    TD_THR_ANY_USER_FLAGS);
+    }
+
+  if (info_verbose)
+    {
+      if (except.reason < 0)
+	exception_fprintf (gdb_stderr, except,
+			   "Warning: find_new_threads_once: ");
+
+      printf_filtered (_("Found %d new threads in iteration %d.\n"),
+		       data.new_threads, iteration);
+    }
+
+  if (errp != NULL)
+    *errp = err;
+
+  return data.new_threads;
+}
+
+/* Search for new threads, accessing memory through stopped thread
+   PTID.  If UNTIL_NO_NEW is true, repeat searching until several
+   searches in a row do not discover any new threads.  */
+
 static void
-thread_db_find_new_threads (void)
+thread_db_find_new_threads_2 (ptid_t ptid, int until_no_new)
 {
   td_err_e err;
+  struct lwp_info *lp;
+  struct thread_db_info *info;
+  int pid = ptid_get_pid (ptid);
+  int i, loop;
+
+  /* In linux, we can only read memory through a stopped lwp.  */
+  ALL_LWPS (lp, ptid)
+    if (lp->stopped && ptid_get_pid (lp->ptid) == pid)
+      break;
 
-  /* Iterate over all user-space threads to discover new threads.  */
-  err = td_ta_thr_iter_p (thread_agent, find_new_threads_callback, NULL,
-			  TD_THR_ANY_STATE, TD_THR_LOWEST_PRIORITY,
-			  TD_SIGNO_MASK, TD_THR_ANY_USER_FLAGS);
-  if (err != TD_OK)
-    error (_("Cannot find new threads: %s"), thread_db_err_str (err));
+  if (!lp)
+    /* There is no stopped thread.  Bail out.  */
+    return;
+
+  info = get_thread_db_info (GET_PID (ptid));
+
+  /* Access an lwp we know is stopped.  */
+  info->proc_handle.ptid = ptid;
+
+  if (until_no_new)
+    {
+      /* Require 4 successive iterations which do not find any new threads.
+	 The 4 is a heuristic: there is an inherent race here, and I have
+	 seen that 2 iterations in a row are not always sufficient to
+	 "capture" all threads.  */
+      for (i = 0, loop = 0; loop < 4; ++i, ++loop)
+	if (find_new_threads_once (info, i, NULL) != 0)
+	  /* Found some new threads.  Restart the loop from beginning.	*/
+	  loop = -1;
+    }
+  else
+    {
+      find_new_threads_once (info, 0, &err);
+      if (err != TD_OK)
+	error (_("Cannot find new threads: %s"), thread_db_err_str (err));
+    }
+}
+
+static void
+thread_db_find_new_threads_1 (ptid_t ptid)
+{
+  thread_db_find_new_threads_2 (ptid, 0);
+}
+
+static int
+update_thread_core (struct lwp_info *info, void *closure)
+{
+  info->core = linux_nat_core_of_thread_1 (info->ptid);
+  return 0;
+}
+
+static void
+thread_db_find_new_threads (struct target_ops *ops)
+{
+  struct thread_db_info *info;
+
+  info = get_thread_db_info (GET_PID (inferior_ptid));
+
+  if (info == NULL)
+    return;
+
+  thread_db_find_new_threads_1 (inferior_ptid);
+
+  iterate_over_lwps (minus_one_ptid /* iterate over all */,
+		     update_thread_core, NULL);
 }
 
 static char *
-thread_db_pid_to_str (ptid_t ptid)
+thread_db_pid_to_str (struct target_ops *ops, ptid_t ptid)
 {
-  if (is_thread (ptid))
+  struct thread_info *thread_info = find_thread_ptid (ptid);
+  struct target_ops *beneath;
+
+  if (thread_info != NULL && thread_info->private != NULL)
     {
       static char buf[64];
-      struct thread_info *thread_info;
+      thread_t tid;
 
-      thread_info = find_thread_pid (ptid);
-      if (thread_info == NULL)
-	snprintf (buf, sizeof (buf), "Thread %ld (LWP %ld) (Missing)",
-		  GET_THREAD (ptid), GET_LWP (ptid));
-      else
-	snprintf (buf, sizeof (buf), "Thread %ld (LWP %ld)",
-		  GET_THREAD (ptid), GET_LWP (ptid));
+      tid = thread_info->private->tid;
+      snprintf (buf, sizeof (buf), "Thread 0x%lx (LWP %ld)",
+		tid, GET_LWP (ptid));
 
       return buf;
     }
 
-  if (target_beneath->to_pid_to_str (ptid))
-    return target_beneath->to_pid_to_str (ptid);
+  beneath = find_target_beneath (ops);
+  if (beneath->to_pid_to_str (beneath, ptid))
+    return beneath->to_pid_to_str (beneath, ptid);
 
   return normal_pid_to_str (ptid);
 }
@@ -1038,6 +1500,9 @@ thread_db_pid_to_str (ptid_t ptid)
 static char *
 thread_db_extra_thread_info (struct thread_info *info)
 {
+  if (info->private == NULL)
+    return NULL;
+
   if (info->private->dying)
     return "Exiting";
 
@@ -1048,31 +1513,44 @@ thread_db_extra_thread_info (struct thread_info *info)
    is stored at OFFSET within the thread local storage for thread PTID.  */
 
 static CORE_ADDR
-thread_db_get_thread_local_address (ptid_t ptid,
+thread_db_get_thread_local_address (struct target_ops *ops,
+				    ptid_t ptid,
 				    CORE_ADDR lm,
 				    CORE_ADDR offset)
 {
-  if (is_thread (ptid))
+  struct thread_info *thread_info;
+  struct target_ops *beneath;
+
+  /* If we have not discovered any threads yet, check now.  */
+  if (!have_threads (ptid))
+    thread_db_find_new_threads_1 (ptid);
+
+  /* Find the matching thread.  */
+  thread_info = find_thread_ptid (ptid);
+
+  if (thread_info != NULL && thread_info->private != NULL)
     {
       td_err_e err;
-      void *address;
-      struct thread_info *thread_info;
+      psaddr_t address;
+      struct thread_db_info *info;
+
+      info = get_thread_db_info (GET_PID (ptid));
 
       /* glibc doesn't provide the needed interface.  */
-      if (!td_thr_tls_get_addr_p)
+      if (!info->td_thr_tls_get_addr_p)
 	throw_error (TLS_NO_LIBRARY_SUPPORT_ERROR,
 		     _("No TLS library support"));
 
       /* Caller should have verified that lm != 0.  */
       gdb_assert (lm != 0);
 
-      /* Get info about the thread.  */
-      thread_info = find_thread_pid (ptid);
-      thread_db_map_id2thr (thread_info, 1);
-
       /* Finally, get the address of the variable.  */
-      err = td_thr_tls_get_addr_p (&thread_info->private->th, (void *) lm,
-				   offset, &address);
+      /* Note the cast through uintptr_t: this interface only works if
+	 a target address fits in a psaddr_t, which is a host pointer.
+	 So a 32-bit debugger can not access 64-bit TLS through this.  */
+      err = info->td_thr_tls_get_addr_p (&thread_info->private->th,
+					 (psaddr_t)(uintptr_t) lm,
+					 offset, &address);
 
 #ifdef THREAD_DB_HAS_TD_NOTALLOC
       /* The memory hasn't been allocated, yet.  */
@@ -1097,27 +1575,73 @@ thread_db_get_thread_local_address (ptid_t ptid,
 	      : (CORE_ADDR) (uintptr_t) address);
     }
 
-  if (target_beneath->to_get_thread_local_address)
-    return target_beneath->to_get_thread_local_address (ptid, lm, offset);
+  beneath = find_target_beneath (ops);
+  if (beneath->to_get_thread_local_address)
+    return beneath->to_get_thread_local_address (beneath, ptid, lm, offset);
   else
     throw_error (TLS_GENERIC_ERROR,
 	         _("TLS not supported on this target"));
 }
 
+/* Callback routine used to find a thread based on the TID part of
+   its PTID.  */
+
+static int
+thread_db_find_thread_from_tid (struct thread_info *thread, void *data)
+{
+  long *tid = (long *) data;
+
+  if (thread->private->tid == *tid)
+    return 1;
+
+  return 0;
+}
+
+/* Implement the to_get_ada_task_ptid target method for this target.  */
+
+static ptid_t
+thread_db_get_ada_task_ptid (long lwp, long thread)
+{
+  struct thread_info *thread_info;
+
+  thread_db_find_new_threads_1 (inferior_ptid);
+  thread_info = iterate_over_threads (thread_db_find_thread_from_tid, &thread);
+
+  gdb_assert (thread_info != NULL);
+
+  return (thread_info->ptid);
+}
+
+static void
+thread_db_resume (struct target_ops *ops,
+		  ptid_t ptid, int step, enum target_signal signo)
+{
+  struct target_ops *beneath = find_target_beneath (ops);
+  struct thread_db_info *info;
+
+  if (ptid_equal (ptid, minus_one_ptid))
+    info = get_thread_db_info (GET_PID (inferior_ptid));
+  else
+    info = get_thread_db_info (GET_PID (ptid));
+
+  /* This workaround is only needed for child fork lwps stopped in a
+     PTRACE_O_TRACEFORK event.  When the inferior is resumed, the
+     workaround can be disabled.  */
+  if (info)
+    info->need_stale_parent_threads_check = 0;
+
+  beneath->to_resume (beneath, ptid, step, signo);
+}
+
 static void
 init_thread_db_ops (void)
 {
   thread_db_ops.to_shortname = "multi-thread";
   thread_db_ops.to_longname = "multi-threaded child process.";
   thread_db_ops.to_doc = "Threads and pthreads support.";
-  thread_db_ops.to_attach = thread_db_attach;
   thread_db_ops.to_detach = thread_db_detach;
-  thread_db_ops.to_resume = thread_db_resume;
   thread_db_ops.to_wait = thread_db_wait;
-  thread_db_ops.to_xfer_partial = thread_db_xfer_partial;
-  thread_db_ops.to_kill = thread_db_kill;
-  thread_db_ops.to_create_inferior = thread_db_create_inferior;
-  thread_db_ops.to_post_startup_inferior = thread_db_post_startup_inferior;
+  thread_db_ops.to_resume = thread_db_resume;
   thread_db_ops.to_mourn_inferior = thread_db_mourn_inferior;
   thread_db_ops.to_find_new_threads = thread_db_find_new_threads;
   thread_db_ops.to_pid_to_str = thread_db_pid_to_str;
@@ -1126,20 +1650,38 @@ init_thread_db_ops (void)
   thread_db_ops.to_get_thread_local_address
     = thread_db_get_thread_local_address;
   thread_db_ops.to_extra_thread_info = thread_db_extra_thread_info;
+  thread_db_ops.to_get_ada_task_ptid = thread_db_get_ada_task_ptid;
   thread_db_ops.to_magic = OPS_MAGIC;
 }
 
+/* Provide a prototype to silence -Wmissing-prototypes.  */
+extern initialize_file_ftype _initialize_thread_db;
+
 void
 _initialize_thread_db (void)
 {
-  /* Only initialize the module if we can load libthread_db.  */
-  if (thread_db_load ())
-    {
-      init_thread_db_ops ();
-      add_target (&thread_db_ops);
-
-      /* Add ourselves to objfile event chain.  */
-      target_new_objfile_chain = deprecated_target_new_objfile_hook;
-      deprecated_target_new_objfile_hook = thread_db_new_objfile;
-    }
+  init_thread_db_ops ();
+  add_target (&thread_db_ops);
+
+  /* Defer loading of libthread_db.so until inferior is running.
+     This allows gdb to load correct libthread_db for a given
+     executable -- there could be mutiple versions of glibc,
+     compiled with LinuxThreads or NPTL, and until there is
+     a running inferior, we can't tell which libthread_db is
+     the correct one to load. */
+
+  libthread_db_search_path = xstrdup (LIBTHREAD_DB_SEARCH_PATH);
+
+  add_setshow_optional_filename_cmd ("libthread-db-search-path",
+				     class_support,
+				     &libthread_db_search_path, _("\
+Set search path for libthread_db."), _("\
+Show the current search path or libthread_db."), _("\
+This path is used to search for libthread_db to be loaded into \
+gdb itself."),
+			    NULL,
+			    NULL,
+			    &setlist, &showlist);
+  /* Add ourselves to objfile event chain.  */
+  observer_attach_new_objfile (thread_db_new_objfile);
 }