* fork-child.c (fork_inferior): Only reset the thread list if this

	is the first inferior.
	(startup_inferior): If the target support multi-process, tell it
	to resume only the new process.
	* linux-nat.c (num_lwps): Delete global.
	(purge_lwp_list): New function.
	(num_lwps): New function.
	(add_lwp, delete_lwp): Adjust.
	(ptid_match): New.
	(iterate_over_lwps): Add filter argument.  Handle it.
	(linux_nat_attach): Remove FIXME note.
	(linux_nat_detach): Adjust to iterate over threads of the inferior
	we're detaching from.  Adjust to num_lwps being a function.  Don't
	assume the head of the lwp list is the main thread of the process
	we're detaching from.  Don't destroy the LWP list.
	(resume_callback): Add debug output.
	(linux_nat_resume): Handle resuming a single inferior.  Allow a
	wildcard resume in non-stop mode.
	(linux_handle_extended_wait): Don't assume inferior_ptid is the
	correct inferior of the parent LWP.
	(status_callback): Also check lp->waitstatus.
	(select_event_lwp): Add new filter parameter.  Handle it.
	(linux_nat_filter_event): Adjust to num_lwps being a function.
	(linux_nat_wait_1): When adding the first lwp of the inferior, use
	an is_lwp check instead of checking for the number of lwps.
	(linux_nat_wait_1): Handle waiting for a specific tgid.  Handle
	pending process exit statuses.
	(linux_nat_mourn_inferior): Don't destroy all the LWP info.
	Instead delete LWPs of the inferior that we're mourning.  Don't
	unregister from the event loop here.
	(linux_nat_pid_to_str): Use `num_lwps'.
	(linux_nat_make_corefile_notes): Adjust to walk over lwps of a
	single inferior.
	(linux_nat_is_async_p): Check if async was masked out.
	(linux_multi_process): New global.
	(linux_nat_supports_multi_process): New.
	(linux_nat_stop_lwp): Remove LWP filtering.  It is done by the
	caller.
	(linux_nat_stop): Adjust to make iterate_over_lwps itself do the
	LWP filtering.
	(linux_nat_close): New.
	(linux_nat_add_target): Register linux_nat_close and
	linux_nat_supports_multi_process.
	* linux-nat.h (iterate_over_lwps): Add filter argument.
	* linux-thread-db.c (thread_db_handle): Delete.
	(proc_handle, thread_agent, td_init_p, td_ta_new_p)
	(td_ta_map_id2thr_p, td_ta_map_lwp2thr_p, td_ta_thr_iter_p)
	(td_ta_event_addr_p, td_ta_set_event_p, td_ta_event_getmsg_p)
	(td_thr_validate_p, td_thr_get_info_p, td_thr_event_enable_p)
	(td_thr_tls_get_addr_p, td_create_bp_addr, td_death_bp_addr): No
	longer globals, moved to...
	(struct thread_db_info): ... this new structure.
	(thread_db_list): New.
	(add_thread_db_info, get_thread_db_info, delete_thread_db_info):
	New.
	(have_threads_callback): Filter out threads of all inferiors but
	the one specified by the ARGS argument.
	(have_threads): Add ptid argument specifying the inferior we're
	interested in.  Handle it.
	(struct thread_get_info_inout): New.
	(thread_get_info_callback, thread_from_lwp): Adjust to use it.
	(thread_db_attach_lwp): Check that inferior of the passed in
	thread is using thread-db.  Adjust.
	(enable_thread_event): Remove thread_agent parameter.  Instead,
	get it from the per-inferior thread-db info.
	(dladdr_to_soname): Move higher up.
	(enable_thread_event_reporting): Adjust to use per-inferior
	thread-db info.
	(try_thread_db_load_1): Replace `handle' parameter by a
	thread_db_info parameter.  Adjust to use per-inferior thread-db
	info.
	(try_thread_db_load): Adjust to use per-inferior thread-db info.
	(thread_db_load, disable_thread_event_reporting): Ditto.
	(check_for_thread_db): Remove conditional reporting of which
	libthread_db is in use.
	(thread_db_new_objfile): Add comment about inferior_ptid.
	(attach_thread): Adjust to use per-inferior thread-db info.
	(thread_db_detach): Adjust to use per-inferior thread-db info.
	Remove thread event breakpoints of the current inferior.  Only
	unpush the thread-db target if there are no more processes using
	it.
	(check_event): Adjust to use per-inferior thread-db info.
	(thread_db_wait): Adjust to use per-inferior thread-db info.  Only
	unpush the thread-db target if there are no more processes using
	it.
	(thread_db_mourn_inferior): Adjust to use per-inferior thread-db
	info.  Mark breakpoints of the current inferior out before
	deleting them.  Only unpush the thread-db target if there are no
	more processes using it.
	(find_new_threads_callback): Adjust to use per-inferior thread_db
	info.
	(thread_db_find_new_threads_1): Add new ptid argument.  Adjust to
	use per-inferior thread-db info.
	(thread_db_find_new_threads): Adjust to use per-inferior thread-db
	info.
	(thread_db_get_thread_local_address): Adjust.
	(thread_db_get_ada_task_ptid): Adjust.
	* inf-ptrace.c (inf_ptrace_mourn_inferior): Only unpush the target
	if there no more processes left to debug.
	* thread.c (set_running, set_executing): Handle resuming all
	threads of a single inferior.
	* mi/mi-interp.c (mi_output_running_pid): New.
	(mi_inferior_count): New.
	(mi_on_resume): For backwards compatibility, if resuming all
	threads of an inferior, and there is only one inferior, output
	"all".

1 files changed, 361 insertions, 216 deletions

diff --git a/gdb/linux-thread-db.c b/gdb/linux-thread-db.c
index 80dd30d..6e68965 100644
--- a/gdb/linux-thread-db.c
+++ b/gdb/linux-thread-db.c
@@ -81,67 +81,146 @@ static char *libthread_db_search_path;
 /* This module's target vector.  */
 static struct target_ops thread_db_ops;
 
-/* Handle from dlopen for libthread_db.so.  Not NULL if we're using this
-   module's target vector.  */
-static void *thread_db_handle;
-
 /* Non-zero if we have determined the signals used by the threads
    library.  */
 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.  */
+  td_thragent_t *thread_agent;
+
+  /* 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;
 
-/* Connection to the libthread_db library.  */
-static td_thragent_t *thread_agent;
+  /* Location of the thread death event breakpoint.  */
+  CORE_ADDR td_death_bp_addr;
 
-/* Pointers to the libthread_db functions.  */
+  /* Pointers to the libthread_db functions.  */
 
-static td_err_e (*td_init_p) (void);
+  td_err_e (*td_init_p) (void);
 
-static td_err_e (*td_ta_new_p) (struct ps_prochandle * ps,
+  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_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,
+				     void *map_address,
+				     size_t offset, void **address);
+};
+
+/* 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);
+
+/* 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.  */
+
+static struct thread_db_info *
+add_thread_db_info (void *handle)
+{
+  int pid;
+  struct thread_db_info *info;
+
+  info = xcalloc (1, sizeof (*info));
+  info->pid = ptid_get_pid (inferior_ptid);
+  info->handle = handle;
+
+  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.  */
+
+static struct thread_db_info *
+get_thread_db_info (int pid)
+{
+  struct thread_db_info *info;
+
+  for (info = thread_db_list; info; info = info->next)
+    if (pid == info->pid)
+      return info;
+
+  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 void thread_db_find_new_threads_1 (void);
 static void attach_thread (ptid_t ptid, const td_thrhandle_t *th_p,
 			   const td_thrinfo_t *ti_p);
 static void detach_thread (ptid_t ptid);
@@ -232,17 +311,29 @@ thread_db_err_str (td_err_e err)
    the threading library is not fully initialized yet.  */
 
 static int
-have_threads_callback (struct thread_info *thread, void *dummy)
+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 (void)
+have_threads (ptid_t ptid)
 {
-  return iterate_over_threads (have_threads_callback, NULL) != NULL;
+  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.
 
@@ -254,45 +345,42 @@ have_threads (void)
    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 (proc_handle.ptid), ti.ti_lid, 0);
-  thread_info = find_thread_pid (thread_ptid);
+  thread_ptid = ptid_build (info->pid, ti.ti_lid, 0);
+  inout->thread_info = find_thread_pid (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;
-      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?).  */
-      if (!have_threads ())
-	thread_db_find_new_threads_1 ();
+      if (!have_threads (thread_ptid))
+ 	thread_db_find_new_threads_1 (thread_ptid);
       else
 	attach_thread (thread_ptid, thp, &ti);
-      thread_info = find_thread_pid (thread_ptid);
-      gdb_assert (thread_info != NULL);
+      inout->thread_info = find_thread_pid (thread_ptid);
+      gdb_assert (inout->thread_info != NULL);
     }
 
-  if (infop != NULL)
-    *(struct thread_info **) infop = thread_info;
-
   return 0;
 }
 
@@ -303,22 +391,23 @@ 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};
 
   /* This ptid comes from linux-nat.c, which should always fill in the
      LWP.  */
   gdb_assert (GET_LWP (ptid) != 0);
 
+  info = get_thread_db_info (GET_PID (ptid));
+
   /* Access an lwp we know is stopped.  */
-  proc_handle.ptid = ptid;
-  err = td_ta_map_lwp2thr_p (thread_agent, GET_LWP (ptid), &th);
+  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
@@ -327,9 +416,11 @@ 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);
+  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;
 
   gdb_assert (ptid_get_tid (ptid) == 0);
   return ptid;
@@ -345,8 +436,11 @@ thread_db_attach_lwp (ptid_t ptid)
   td_thrhandle_t th;
   td_thrinfo_t ti;
   td_err_e err;
+  struct thread_db_info *info;
 
-  if (thread_db_handle == NULL)
+  info = get_thread_db_info (GET_PID (ptid));
+
+  if (info == NULL)
     return 0;
 
   /* This ptid comes from linux-nat.c, which should always fill in the
@@ -354,20 +448,20 @@ thread_db_attach_lwp (ptid_t ptid)
   gdb_assert (GET_LWP (ptid) != 0);
 
   /* Access an lwp we know is stopped.  */
-  proc_handle.ptid = ptid;
+  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 ())
-    thread_db_find_new_threads_1 ();
+  if (!have_threads (ptid))
+    thread_db_find_new_threads_1 (ptid);
 
-  err = td_ta_map_lwp2thr_p (thread_agent, GET_LWP (ptid), &th);
+  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;
 
-  err = td_thr_get_info_p (&th, &ti);
+  err = info->td_thr_get_info_p (&th, &ti);
   if (err != TD_OK)
     {
       warning (_("Cannot get thread info: %s"), thread_db_err_str (err));
@@ -388,16 +482,19 @@ verbose_dlsym (void *handle, const char *name)
 }
 
 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.  */
-  proc_handle.ptid = inferior_ptid;
+  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;
 
@@ -425,11 +522,16 @@ enable_thread_event_reporting (void)
   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.  */
@@ -446,7 +548,7 @@ enable_thread_event_reporting (void)
 #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"),
@@ -456,11 +558,11 @@ 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"),
@@ -469,7 +571,7 @@ 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"),
@@ -478,6 +580,20 @@ enable_thread_event_reporting (void)
     }
 }
 
+/* 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,
@@ -485,36 +601,35 @@ enable_thread_event_reporting (void)
    version mismatch between libthread_db and libpthread).  */
 
 static int
-try_thread_db_load_1 (void *handle)
+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.  */
 
-  td_init_p = verbose_dlsym (handle, "td_init");
-  if (td_init_p == NULL)
+  info->td_init_p = verbose_dlsym (info->handle, "td_init");
+  if (info->td_init_p == NULL)
     return 0;
 
-  err = td_init_p ();
+  err = info->td_init_p ();
   if (err != TD_OK)
     {
       warning (_("Cannot initialize libthread_db: %s"), thread_db_err_str (err));
       return 0;
     }
 
-  td_ta_new_p = verbose_dlsym (handle, "td_ta_new");
-  if (td_ta_new_p == NULL)
+  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.  */
-  proc_handle.ptid = inferior_ptid;
+  info->proc_handle.ptid = inferior_ptid;
 
   /* Now attempt to open a connection to the thread library.  */
-  err = td_ta_new_p (&proc_handle, &thread_agent);
+  err = info->td_ta_new_p (&info->proc_handle, &info->thread_agent);
   if (err != TD_OK)
     {
-      td_ta_new_p = NULL;
       if (info_verbose)
 	printf_unfiltered (_("td_ta_new failed: %s\n"),
 			   thread_db_err_str (err));
@@ -535,56 +650,55 @@ try_thread_db_load_1 (void *handle)
       return 0;
     }
 
-  td_ta_map_id2thr_p = verbose_dlsym (handle, "td_ta_map_id2thr");
-  if (td_ta_map_id2thr_p == NULL)
+  info->td_ta_map_id2thr_p = verbose_dlsym (info->handle, "td_ta_map_id2thr");
+  if (info->td_ta_map_id2thr_p == NULL)
     return 0;
 
-  td_ta_map_lwp2thr_p = verbose_dlsym (handle, "td_ta_map_lwp2thr");
-  if (td_ta_map_lwp2thr_p == NULL)
+  info->td_ta_map_lwp2thr_p = verbose_dlsym (info->handle, "td_ta_map_lwp2thr");
+  if (info->td_ta_map_lwp2thr_p == NULL)
     return 0;
 
-  td_ta_thr_iter_p = verbose_dlsym (handle, "td_ta_thr_iter");
-  if (td_ta_thr_iter_p == NULL)
+  info->td_ta_thr_iter_p = verbose_dlsym (info->handle, "td_ta_thr_iter");
+  if (info->td_ta_thr_iter_p == NULL)
     return 0;
 
-  td_thr_validate_p = verbose_dlsym (handle, "td_thr_validate");
-  if (td_thr_validate_p == NULL)
+  info->td_thr_validate_p = verbose_dlsym (info->handle, "td_thr_validate");
+  if (info->td_thr_validate_p == NULL)
     return 0;
 
-  td_thr_get_info_p = verbose_dlsym (handle, "td_thr_get_info");
-  if (td_thr_get_info_p == NULL)
+  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.  */
-  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");
+  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_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"));
 
-  /* The thread library was detected.  Activate the thread_db target.  */
-  push_target (&thread_db_ops);
-  thread_db_handle = handle;
+  if (info_verbose || *libthread_db_search_path)
+    {
+      const char *library;
 
-  enable_thread_event_reporting ();
-  thread_db_find_new_threads_1 ();
-  return 1;
-}
+      library = dladdr_to_soname (*info->td_ta_new_p);
+      if (library == NULL)
+	library = LIBTHREAD_DB_SO;
 
-/* Lookup a library in which given symbol resides.
-   Note: this is looking in GDB process, not in the inferior.
-   Returns library name, or NULL.  */
+      printf_unfiltered (_("Using host libthread_db library \"%s\".\n"),
+			 library);
+    }
 
-static const char *
-dladdr_to_soname (const void *addr)
-{
-  Dl_info info;
+  /* 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);
 
-  if (dladdr (addr, &info) != 0)
-    return info.dli_fname;
-  return NULL;
+  enable_thread_event_reporting ();
+  thread_db_find_new_threads_1 (inferior_ptid);
+  return 1;
 }
 
 /* Attempt to use LIBRARY as libthread_db.  LIBRARY could be absolute,
@@ -594,6 +708,7 @@ 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"),
@@ -621,11 +736,13 @@ try_thread_db_load (const char *library)
         }
     }
 
-  if (try_thread_db_load_1 (handle))
+  info = add_thread_db_info (handle);
+
+  if (try_thread_db_load_1 (info))
     return 1;
 
   /* This library "refused" to work on current inferior.  */
-  dlclose (handle);
+  delete_thread_db_info (GET_PID (inferior_ptid));
   return 0;
 }
 
@@ -695,8 +812,11 @@ static int
 thread_db_load (void)
 {
   struct objfile *obj;
+  struct thread_db_info *info;
 
-  if (thread_db_handle != NULL)
+  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
@@ -754,16 +874,19 @@ static void
 disable_thread_event_reporting (void)
 {
   td_thr_events_t events;
+  struct thread_db_info *info;
+
+  info = get_thread_db_info (GET_PID (inferior_ptid));
 
   /* 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);
+  info->td_ta_set_event_p (info->thread_agent, &events);
 
   /* Delete 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;
 }
 
 static void
@@ -807,35 +930,14 @@ check_for_thread_db (void)
   /* Do nothing if we couldn't load libthread_db.so.1.  */
   if (!thread_db_load ())
     return;
-
-  /* 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.
-     We track td_ta_new_p because the user may switch executables,
-     and as a result we may decide to use a different version of
-     libthread_db. */
-
-  if (last_loaded != td_ta_new_p)
-    {
-      last_loaded = td_ta_new_p;
-
-      if (info_verbose || *libthread_db_search_path)
-        {
-          const char *library;
-
-          library = dladdr_to_soname (*td_ta_new_p);
-          if (library == NULL)
-            library = LIBTHREAD_DB_SO;
-
-          printf_unfiltered (_("Using host libthread_db library \"%s\".\n"),
-                             library);
-        }
-    }
 }
 
 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 ();
 }
@@ -851,6 +953,7 @@ attach_thread (ptid_t ptid, const td_thrhandle_t *th_p,
   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
@@ -913,8 +1016,10 @@ attach_thread (ptid_t ptid, const td_thrhandle_t *th_p,
   else
     tp->private = private;
 
+  info = get_thread_db_info (GET_PID (ptid));
+
   /* Enable thread event reporting for this thread.  */
-  err = td_thr_event_enable_p (th_p, 1);
+  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));
@@ -942,20 +1047,32 @@ static void
 thread_db_detach (struct target_ops *ops, char *args, int from_tty)
 {
   struct target_ops *target_beneath = find_target_beneath (ops);
+  struct thread_db_info *info;
 
-  disable_thread_event_reporting ();
+  info = get_thread_db_info (GET_PID (inferior_ptid));
 
-  /* Forget about the child's process ID.  We shouldn't need it
-     anymore.  */
-  proc_handle.ptid = null_ptid;
+  if (info)
+    {
+      disable_thread_event_reporting ();
 
-  /* Detach thread_db target ops.  */
-  unpush_target (&thread_db_ops);
-  if (thread_db_handle)
-    dlclose (thread_db_handle);
-  thread_db_handle = NULL;
+      /* 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 ();
+
+      delete_thread_db_info (GET_PID (inferior_ptid));
+    }
 
   target_beneath->to_detach (target_beneath, args, from_tty);
+
+  /* NOTE: From this point on, inferior_ptid is null_ptid.  */
+
+  /* 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
@@ -972,21 +1089,25 @@ check_event (ptid_t ptid)
   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 = regcache_read_pc (regcache)
 	    - gdbarch_decr_pc_after_break (gdbarch);
-  if (stop_pc != td_create_bp_addr && stop_pc != td_death_bp_addr)
+  if (stop_pc != info->td_create_bp_addr
+      && stop_pc != info->td_death_bp_addr)
     return;
 
   /* Access an lwp we know is stopped.  */
-  proc_handle.ptid = ptid;
+  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 ())
-    thread_db_find_new_threads_1 ();
+  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.
@@ -1006,7 +1127,7 @@ 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)
@@ -1016,7 +1137,7 @@ 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));
 
@@ -1051,6 +1172,7 @@ static ptid_t
 thread_db_wait (struct target_ops *ops,
 		ptid_t ptid, struct target_waitstatus *ourstatus)
 {
+  struct thread_db_info *info;
   struct target_ops *beneath = find_target_beneath (ops);
 
   ptid = beneath->to_wait (beneath, ptid, ourstatus);
@@ -1062,28 +1184,40 @@ thread_db_wait (struct target_ops *ops,
       || ourstatus->kind == TARGET_WAITKIND_SIGNALLED)
     return ptid;
 
+  info = get_thread_db_info (GET_PID (ptid));
+
+  /* If this process isn't using thread_db, we're done.  */
+  if (info == NULL)
+    return ptid;
+
   if (ourstatus->kind == TARGET_WAITKIND_EXECD)
     {
+      /* Breakpoints have already been marked non-inserted by the
+	 layer below.  We're safe in knowing that removing them will
+	 not write the shadows of the old image into the new
+	 image.  */
       remove_thread_event_breakpoints ();
-      unpush_target (&thread_db_ops);
-      if (thread_db_handle)
-	dlclose (thread_db_handle);
-      thread_db_handle = NULL;
+
+      /* 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);
 
       return ptid;
     }
 
   /* 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 ())
-    thread_db_find_new_threads_1 ();
+  if (ourstatus->kind == TARGET_WAITKIND_STOPPED && !have_threads (ptid))
+    thread_db_find_new_threads_1 (ptid);
 
   if (ourstatus->kind == TARGET_WAITKIND_STOPPED
       && ourstatus->value.sig == TARGET_SIGNAL_TRAP)
     /* Check for a thread event.  */
     check_event (ptid);
 
-  if (have_threads ())
+  if (have_threads (ptid))
     {
       /* Change ptids back into the higher level PID + TID format.  If
 	 the thread is dead and no longer on the thread list, we will
@@ -1104,21 +1238,18 @@ thread_db_mourn_inferior (struct target_ops *ops)
 {
   struct target_ops *target_beneath = find_target_beneath (ops);
 
-  /* Forget about the child's process ID.  We shouldn't need it
-     anymore.  */
-  proc_handle.ptid = null_ptid;
+  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.  */
+  /* Delete the old thread event breakpoints.  Mark breakpoints out,
+     so that we don't try to un-insert them.  */
+  mark_breakpoints_out ();
   remove_thread_event_breakpoints ();
 
+  target_beneath->to_mourn_inferior (target_beneath);
+
   /* Detach thread_db target ops.  */
-  unpush_target (ops);
-  if (thread_db_handle)
-    dlclose (thread_db_handle);
-  thread_db_handle = NULL;
+  if (!thread_db_list)
+    unpush_target (ops);
 }
 
 static int
@@ -1128,8 +1259,9 @@ find_new_threads_callback (const td_thrhandle_t *th_p, void *data)
   td_err_e err;
   ptid_t ptid;
   struct thread_info *tp;
+  struct thread_db_info *info = data;
 
-  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));
@@ -1137,7 +1269,7 @@ 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 (proc_handle.ptid), ti.ti_lid, 0);
+  ptid = ptid_build (info->pid, ti.ti_lid, 0);
 
   if (ti.ti_tid == 0)
     {
@@ -1147,7 +1279,7 @@ find_new_threads_callback (const td_thrhandle_t *th_p, void *data)
 	 be yet.  Just enable event reporting and otherwise ignore
 	 it.  */
 
-      err = td_thr_event_enable_p (th_p, 1);
+      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));
@@ -1166,27 +1298,30 @@ find_new_threads_callback (const td_thrhandle_t *th_p, void *data)
    PTID.  */
 
 static void
-thread_db_find_new_threads_1 (void)
+thread_db_find_new_threads_1 (ptid_t ptid)
 {
   td_err_e err;
   struct lwp_info *lp;
-  ptid_t ptid;
+  struct thread_db_info *info;
+  int pid = ptid_get_pid (ptid);
 
   /* In linux, we can only read memory through a stopped lwp.  */
   ALL_LWPS (lp, ptid)
-    if (lp->stopped)
+    if (lp->stopped && ptid_get_pid (lp->ptid) == pid)
       break;
 
   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.  */
-  proc_handle.ptid = ptid;
+  info->proc_handle.ptid = ptid;
   /* 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);
+  err = info->td_ta_thr_iter_p (info->thread_agent, find_new_threads_callback,
+				info, 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));
 }
@@ -1194,7 +1329,14 @@ thread_db_find_new_threads_1 (void)
 static void
 thread_db_find_new_threads (struct target_ops *ops)
 {
-  thread_db_find_new_threads_1 ();
+  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);
 }
 
 static char *
@@ -1250,8 +1392,8 @@ thread_db_get_thread_local_address (struct target_ops *ops,
   struct target_ops *beneath;
 
   /* If we have not discovered any threads yet, check now.  */
-  if (!have_threads ())
-    thread_db_find_new_threads_1 ();
+  if (!have_threads (ptid))
+    thread_db_find_new_threads_1 (ptid);
 
   /* Find the matching thread.  */
   thread_info = find_thread_pid (ptid);
@@ -1260,9 +1402,12 @@ thread_db_get_thread_local_address (struct target_ops *ops,
     {
       td_err_e err;
       void *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"));
 
@@ -1270,9 +1415,9 @@ thread_db_get_thread_local_address (struct target_ops *ops,
       gdb_assert (lm != 0);
 
       /* Finally, get the address of the variable.  */
-      err = td_thr_tls_get_addr_p (&thread_info->private->th,
-				   (void *)(size_t) lm,
-				   offset, &address);
+      err = info->td_thr_tls_get_addr_p (&thread_info->private->th,
+					 (void *)(size_t) lm,
+					 offset, &address);
 
 #ifdef THREAD_DB_HAS_TD_NOTALLOC
       /* The memory hasn't been allocated, yet.  */
@@ -1326,7 +1471,7 @@ thread_db_get_ada_task_ptid (long lwp, long thread)
 {
   struct thread_info *thread_info;
 
-  thread_db_find_new_threads_1 ();
+  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);