Push pruning old threads down to the target

When GDB wants to sync the thread list with the target's (e.g., due to
"info threads"), it calls update_thread_list:

 update_thread_list (void)
 {
   prune_threads ();
   target_find_new_threads ();
   update_threads_executing ();
 }

And then prune_threads does:

 prune_threads (void)
 {
   struct thread_info *tp, *next;

   for (tp = thread_list; tp; tp = next)
     {
       next = tp->next;
       if (!thread_alive (tp))
	 delete_thread (tp->ptid);
     }
 }

Calling thread_live on each thread one by one is expensive.

E.g., on Linux, it ends up doing kill(SIG0) once for each thread.  Not
a big deal, but still a bunch of syscalls...

With the remote target, it's cumbersome.  That thread_alive call ends
up generating one T packet per thread:

 Sending packet: $Tp2141.2150#82...Packet received: OK
 Sending packet: $Tp2141.214f#b7...Packet received: OK
 Sending packet: $Tp2141.2141#82...Packet received: OK
 Sending packet: $qXfer:threads:read::0,fff#03...Packet received: l<threads>\n<thread id="p2141.2141" core="2"/>\n<thread id="p2141.214f" core="1"/>\n<thread id="p2141.2150" core="2"/>\n</threads>\n

That seems a bit silly when target_find_new_threads method
implementations will always fetch the whole current set of target
threads, and then add those that are not in GDB's thread list, to
GDB's thread list.

This patch thus pushes down the responsibility of pruning dead threads
to the target_find_new_threads method instead, so a target may
implement pruning dead threads however it wants.

Once we do that, target_find_new_threads becomes a misnomer, so the
patch renames it to target_update_thread_list.

The patch doesn't attempt to do any optimization to any target yet.
It simply exports prune_threads, and makes all implementations of
target_update_thread_list call that.  It's meant to be a no-op.

gdb/
2014-10-15  Pedro Alves  <palves@redhat.com>

	* ada-tasks.c (print_ada_task_info, task_command_1): Adjust.
	* bsd-uthread.c (bsd_uthread_find_new_threads): Rename to ...
	(bsd_uthread_update_thread_list): ... this.  Call prune_threads.
	(bsd_uthread_target): Adjust.
	* corelow.c (core_open): Adjust.
	* dec-thread.c (dec_thread_find_new_threads): Update comment.
	(dec_thread_update_thread_list): New function.
	(init_dec_thread_ops): Adjust.
	* gdbthread.h (prune_threads): New declaration.
	* linux-thread-db.c (thread_db_find_new_threads): Rename to ...
	(thread_db_update_thread_list): ... this.  Call prune_threads.
	(init_thread_db_ops): Adjust.
	* nto-procfs.c (procfs_find_new_threads): Rename to ...
	(procfs_update_thread_list): ... this.  Call prune_threads.
	(procfs_attach, procfs_create_inferior, init_procfs_targets):
	Adjust.
	* obsd-nat.c (obsd_find_new_threads): Rename to ...
	(obsd_update_thread_list): ... this.  Call prune_threads.
	(obsd_add_target): Adjust.
	* procfs.c (procfs_target): Adjust.
	(procfs_notice_thread): Update comment.
	(procfs_find_new_threads): Rename to ...
	(procfs_update_thread_list): ... this.  Call prune_threads.
	* ravenscar-thread.c (ravenscar_update_inferior_ptid): Update
	comment.
	(ravenscar_wait): Adjust.
	(ravenscar_find_new_threads): Rename to ...
	(ravenscar_update_thread_list): ... this.  Call prune_threads.
	(init_ravenscar_thread_ops): Adjust.
	* record-btrace.c (record_btrace_find_new_threads): Rename to ...
	(record_btrace_update_thread_list): ... this.  Adjust comment.
	(init_record_btrace_ops): Adjust.
	* remote.c (remote_threads_info): Rename to ...
	(remote_update_thread_list): ... this.  Call prune_threads.
	(remote_start_remote, extended_remote_attach_1, init_remote_ops):
	Adjust.
	* sol-thread.c (check_for_thread_db): Adjust.
	(sol_find_new_threads_callback): Rename to ...
	(sol_update_thread_list_callback): ... this.
	(sol_find_new_threads): Rename to ...
	(sol_update_thread_list): ... this.  Call prune_threads.  Adjust.
	(sol_get_ada_task_ptid, init_sol_thread_ops): Adjust.
	* target-delegates.c: Regenerate.
	* target.c (target_find_new_threads): Rename to ...
	(target_update_thread_list): ... this.
	* target.h (struct target_ops): Rename to_find_new_threads field
	to to_update_thread_list.
	(target_find_new_threads): Rename to ...
	(target_update_thread_list): ... this.
	* thread.c (prune_threads): Make extern.
	(update_thread_list): Adjust.

18 files changed, 154 insertions, 65 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 0549f4a..3a6bffd 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,59 @@
 2014-10-15  Pedro Alves  <palves@redhat.com>
 
+	* ada-tasks.c (print_ada_task_info, task_command_1): Adjust.
+	* bsd-uthread.c (bsd_uthread_find_new_threads): Rename to ...
+	(bsd_uthread_update_thread_list): ... this.  Call prune_threads.
+	(bsd_uthread_target): Adjust.
+	* corelow.c (core_open): Adjust.
+	* dec-thread.c (dec_thread_find_new_threads): Update comment.
+	(dec_thread_update_thread_list): New function.
+	(init_dec_thread_ops): Adjust.
+	* gdbthread.h (prune_threads): New declaration.
+	* linux-thread-db.c (thread_db_find_new_threads): Rename to ...
+	(thread_db_update_thread_list): ... this.  Call prune_threads.
+	(init_thread_db_ops): Adjust.
+	* nto-procfs.c (procfs_find_new_threads): Rename to ...
+	(procfs_update_thread_list): ... this.  Call prune_threads.
+	(procfs_attach, procfs_create_inferior, init_procfs_targets):
+	Adjust.
+	* obsd-nat.c (obsd_find_new_threads): Rename to ...
+	(obsd_update_thread_list): ... this.  Call prune_threads.
+	(obsd_add_target): Adjust.
+	* procfs.c (procfs_target): Adjust.
+	(procfs_notice_thread): Update comment.
+	(procfs_find_new_threads): Rename to ...
+	(procfs_update_thread_list): ... this.  Call prune_threads.
+	* ravenscar-thread.c (ravenscar_update_inferior_ptid): Update
+	comment.
+	(ravenscar_wait): Adjust.
+	(ravenscar_find_new_threads): Rename to ...
+	(ravenscar_update_thread_list): ... this.  Call prune_threads.
+	(init_ravenscar_thread_ops): Adjust.
+	* record-btrace.c (record_btrace_find_new_threads): Rename to ...
+	(record_btrace_update_thread_list): ... this.  Adjust comment.
+	(init_record_btrace_ops): Adjust.
+	* remote.c (remote_threads_info): Rename to ...
+	(remote_update_thread_list): ... this.  Call prune_threads.
+	(remote_start_remote, extended_remote_attach_1, init_remote_ops):
+	Adjust.
+	* sol-thread.c (check_for_thread_db): Adjust.
+	(sol_find_new_threads_callback): Rename to ...
+	(sol_update_thread_list_callback): ... this.
+	(sol_find_new_threads): Rename to ...
+	(sol_update_thread_list): ... this.  Call prune_threads.  Adjust.
+	(sol_get_ada_task_ptid, init_sol_thread_ops): Adjust.
+	* target-delegates.c: Regenerate.
+	* target.c (target_find_new_threads): Rename to ...
+	(target_update_thread_list): ... this.
+	* target.h (struct target_ops): Rename to_find_new_threads field
+	to to_update_thread_list.
+	(target_find_new_threads): Rename to ...
+	(target_update_thread_list): ... this.
+	* thread.c (prune_threads): Make extern.
+	(update_thread_list): Adjust.
+
+2014-10-15  Pedro Alves  <palves@redhat.com>
+
 	* remote.c (remote_get_threadlist, remote_threadlist_iterator):
 	Add describing comment.  Return -1 if the qL packet is not
 	supported.
diff --git a/gdb/ada-tasks.c b/gdb/ada-tasks.c
index 585c1f6..2d5a19d 100644
--- a/gdb/ada-tasks.c
+++ b/gdb/ada-tasks.c
@@ -1025,7 +1025,7 @@ print_ada_task_info (struct ui_out *uiout,
        take a --thread argument.  However, in order to be able to
        provide that thread ID, the thread list must be up to date
        first.  */
-    target_find_new_threads ();
+    target_update_thread_list ();
 
   data = get_ada_tasks_inferior_data (inf);
 
@@ -1291,7 +1291,7 @@ task_command_1 (char *taskno_str, int from_tty, struct inferior *inf)
      to the thread associated to our task if GDB does not know about
      that thread, we need to make sure that any new threads gets added
      to the thread list.  */
-  target_find_new_threads ();
+  target_update_thread_list ();
 
   /* Verify that the ptid of the task we want to switch to is valid
      (in other words, a ptid that GDB knows about).  Otherwise, we will
diff --git a/gdb/bsd-uthread.c b/gdb/bsd-uthread.c
index 817a14b..ebe27be 100644
--- a/gdb/bsd-uthread.c
+++ b/gdb/bsd-uthread.c
@@ -412,12 +412,14 @@ bsd_uthread_thread_alive (struct target_ops *ops, ptid_t ptid)
 }
 
 static void
-bsd_uthread_find_new_threads (struct target_ops *ops)
+bsd_uthread_update_thread_list (struct target_ops *ops)
 {
   pid_t pid = ptid_get_pid (inferior_ptid);
   int offset = bsd_uthread_thread_next_offset;
   CORE_ADDR addr;
 
+  prune_threads ();
+
   addr = bsd_uthread_read_memory_address (bsd_uthread_thread_list_addr);
   while (addr != 0)
     {
@@ -516,7 +518,7 @@ bsd_uthread_target (void)
   t->to_wait = bsd_uthread_wait;
   t->to_resume = bsd_uthread_resume;
   t->to_thread_alive = bsd_uthread_thread_alive;
-  t->to_find_new_threads = bsd_uthread_find_new_threads;
+  t->to_update_thread_list = bsd_uthread_update_thread_list;
   t->to_extra_thread_info = bsd_uthread_extra_thread_info;
   t->to_pid_to_str = bsd_uthread_pid_to_str;
   t->to_stratum = thread_stratum;
diff --git a/gdb/corelow.c b/gdb/corelow.c
index dc22f2b..b91ad22 100644
--- a/gdb/corelow.c
+++ b/gdb/corelow.c
@@ -413,7 +413,7 @@ core_open (const char *arg, int from_tty)
      sections.  */
   TRY_CATCH (except, RETURN_MASK_ERROR)
     {
-      target_find_new_threads ();
+      target_update_thread_list ();
     }
 
   if (except.reason < 0)
diff --git a/gdb/dec-thread.c b/gdb/dec-thread.c
index 080640d..fc43153 100644
--- a/gdb/dec-thread.c
+++ b/gdb/dec-thread.c
@@ -394,7 +394,7 @@ dec_thread_add_gdb_thread (struct thread_info *info, void *context)
   return 0;
 }
 
-/* Implement the find_new_thread target_ops method.  */
+/* Find new threads.  */
 
 static void
 dec_thread_find_new_threads (struct target_ops *ops)
@@ -412,6 +412,21 @@ dec_thread_find_new_threads (struct target_ops *ops)
     }
 }
 
+/* Implement the update_thread_list target_ops method.  */
+
+static void
+dec_thread_update_thread_list (struct target_ops *ops)
+{
+  int i;
+  struct dec_thread_info *info;
+
+  /* Delete dead threads.  */
+  prune_threads ();
+
+  /* Now find new threads.  */
+  dec_thread_find_new_threads (ops);
+}
+
 /* Resynchronize the list of threads known by GDB with the actual
    list of threads reported by libpthread_debug.  */
 
@@ -717,7 +732,7 @@ init_dec_thread_ops (void)
   dec_thread_ops.to_store_registers    = dec_thread_store_registers;
   dec_thread_ops.to_mourn_inferior     = dec_thread_mourn_inferior;
   dec_thread_ops.to_thread_alive       = dec_thread_thread_alive;
-  dec_thread_ops.to_find_new_threads   = dec_thread_find_new_threads;
+  dec_thread_ops.to_update_thread_list = dec_thread_update_thread_list;
   dec_thread_ops.to_pid_to_str         = dec_thread_pid_to_str;
   dec_thread_ops.to_stratum            = thread_stratum;
   dec_thread_ops.to_get_ada_task_ptid  = dec_thread_get_ada_task_ptid;
diff --git a/gdb/gdbthread.h b/gdb/gdbthread.h
index 178fd4a..1ed98a2 100644
--- a/gdb/gdbthread.h
+++ b/gdb/gdbthread.h
@@ -444,6 +444,10 @@ extern struct thread_info* inferior_thread (void);
 
 extern void update_thread_list (void);
 
+/* Delete any thread the target says is no longer alive.  */
+
+extern void prune_threads (void);
+
 /* Return true if PC is in the stepping range of THREAD.  */
 
 int pc_in_thread_step_range (CORE_ADDR pc, struct thread_info *thread);
diff --git a/gdb/linux-thread-db.c b/gdb/linux-thread-db.c
index ff5f2cc..352fac1 100644
--- a/gdb/linux-thread-db.c
+++ b/gdb/linux-thread-db.c
@@ -1717,11 +1717,13 @@ update_thread_core (struct lwp_info *info, void *closure)
 }
 
 static void
-thread_db_find_new_threads (struct target_ops *ops)
+thread_db_update_thread_list (struct target_ops *ops)
 {
   struct thread_db_info *info;
   struct inferior *inf;
 
+  prune_threads ();
+
   ALL_INFERIORS (inf)
     {
       struct thread_info *thread;
@@ -2074,7 +2076,7 @@ init_thread_db_ops (void)
   thread_db_ops.to_wait = thread_db_wait;
   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_update_thread_list = thread_db_update_thread_list;
   thread_db_ops.to_pid_to_str = thread_db_pid_to_str;
   thread_db_ops.to_stratum = thread_stratum;
   thread_db_ops.to_has_thread_control = tc_schedlock;
diff --git a/gdb/nto-procfs.c b/gdb/nto-procfs.c
index 8a10d3d..d059624 100644
--- a/gdb/nto-procfs.c
+++ b/gdb/nto-procfs.c
@@ -307,7 +307,7 @@ update_thread_private_data (struct thread_info *new_thread,
 }
 
 static void
-procfs_find_new_threads (struct target_ops *ops)
+procfs_update_thread_list (struct target_ops *ops)
 {
   procfs_status status;
   pid_t pid;
@@ -318,6 +318,8 @@ procfs_find_new_threads (struct target_ops *ops)
   if (ctl_fd == -1)
     return;
 
+  prune_threads ();
+
   pid = ptid_get_pid (inferior_ptid);
 
   status.tid = 1;
@@ -631,7 +633,7 @@ procfs_attach (struct target_ops *ops, const char *args, int from_tty)
   if (!target_is_pushed (ops))
     push_target (ops);
 
-  procfs_find_new_threads (ops);
+  procfs_update_thread_list (ops);
 }
 
 static void
@@ -1195,7 +1197,7 @@ procfs_create_inferior (struct target_ops *ops, char *exec_file,
     close (fds[2]);
 
   inferior_ptid = do_attach (pid_to_ptid (pid));
-  procfs_find_new_threads (ops);
+  procfs_update_thread_list (ops);
 
   inf = current_inferior ();
   inferior_appeared (inf, pid);
@@ -1440,7 +1442,7 @@ init_procfs_targets (void)
   t->to_mourn_inferior = procfs_mourn_inferior;
   t->to_pass_signals = procfs_pass_signals;
   t->to_thread_alive = procfs_thread_alive;
-  t->to_find_new_threads = procfs_find_new_threads;
+  t->to_update_thread_list = procfs_update_thread_list;
   t->to_pid_to_str = procfs_pid_to_str;
   t->to_stop = procfs_stop;
   t->to_have_continuable_watchpoint = 1;
diff --git a/gdb/obsd-nat.c b/gdb/obsd-nat.c
index e4a98ae..94bf56a 100644
--- a/gdb/obsd-nat.c
+++ b/gdb/obsd-nat.c
@@ -50,11 +50,13 @@ obsd_pid_to_str (struct target_ops *ops, ptid_t ptid)
 }
 
 static void
-obsd_find_new_threads (struct target_ops *ops)
+obsd_update_thread_list (struct target_ops *ops)
 {
   pid_t pid = ptid_get_pid (inferior_ptid);
   struct ptrace_thread_state pts;
 
+  prune_threads ();
+
   if (ptrace (PT_GET_THREAD_FIRST, pid, (caddr_t)&pts, sizeof pts) == -1)
     perror_with_name (("ptrace"));
 
@@ -168,7 +170,7 @@ obsd_add_target (struct target_ops *t)
 {
   /* Override some methods to support threads.  */
   t->to_pid_to_str = obsd_pid_to_str;
-  t->to_find_new_threads = obsd_find_new_threads;
+  t->to_update_thread_list = obsd_update_thread_list;
   t->to_wait = obsd_wait;
   add_target (t);
 }
diff --git a/gdb/procfs.c b/gdb/procfs.c
index 15a0409..bd91a46 100644
--- a/gdb/procfs.c
+++ b/gdb/procfs.c
@@ -133,7 +133,7 @@ static target_xfer_partial_ftype procfs_xfer_partial;
 
 static int procfs_thread_alive (struct target_ops *ops, ptid_t);
 
-static void procfs_find_new_threads (struct target_ops *ops);
+static void procfs_update_thread_list (struct target_ops *ops);
 static char *procfs_pid_to_str (struct target_ops *, ptid_t);
 
 static int proc_find_memory_regions (struct target_ops *self,
@@ -196,7 +196,7 @@ procfs_target (void)
   t->to_files_info = procfs_files_info;
   t->to_stop = procfs_stop;
 
-  t->to_find_new_threads = procfs_find_new_threads;
+  t->to_update_thread_list = procfs_update_thread_list;
   t->to_thread_alive = procfs_thread_alive;
   t->to_pid_to_str = procfs_pid_to_str;
 
@@ -4646,7 +4646,7 @@ procfs_inferior_created (struct target_ops *ops, int from_tty)
 #endif
 }
 
-/* Callback for find_new_threads.  Calls "add_thread".  */
+/* Callback for update_thread_list.  Calls "add_thread".  */
 
 static int
 procfs_notice_thread (procinfo *pi, procinfo *thread, void *ptr)
@@ -4663,10 +4663,12 @@ procfs_notice_thread (procinfo *pi, procinfo *thread, void *ptr)
    back to GDB to add to its list.  */
 
 static void
-procfs_find_new_threads (struct target_ops *ops)
+procfs_update_thread_list (struct target_ops *ops)
 {
   procinfo *pi;
 
+  prune_threads ();
+
   /* Find procinfo for main process.  */
   pi = find_procinfo_or_die (ptid_get_pid (inferior_ptid), 0);
   proc_update_threads (pi);
diff --git a/gdb/ravenscar-thread.c b/gdb/ravenscar-thread.c
index acee55e..f1db1a8 100644
--- a/gdb/ravenscar-thread.c
+++ b/gdb/ravenscar-thread.c
@@ -52,7 +52,7 @@ static const char first_task_name[] = "system__tasking__debug__first_task";
 static const char ravenscar_runtime_initializer[] =
   "system__bb__threads__initialize";
 
-static void ravenscar_find_new_threads (struct target_ops *ops);
+static void ravenscar_update_thread_list (struct target_ops *ops);
 static ptid_t ravenscar_running_thread (void);
 static char *ravenscar_extra_thread_info (struct target_ops *self,
 					  struct thread_info *tp);
@@ -91,7 +91,7 @@ ravenscar_update_inferior_ptid (void)
   gdb_assert (!ptid_equal (inferior_ptid, null_ptid));
 
   /* The running thread may not have been added to
-     system.tasking.debug's list yet; so ravenscar_find_new_threads
+     system.tasking.debug's list yet; so ravenscar_update_thread_list
      may not always add it to the thread list.  Add it here.  */
   if (!find_thread_ptid (inferior_ptid))
     add_thread (inferior_ptid);
@@ -201,7 +201,7 @@ ravenscar_wait (struct target_ops *ops, ptid_t ptid,
   if (status->kind != TARGET_WAITKIND_EXITED
       && status->kind != TARGET_WAITKIND_SIGNALLED)
     {
-      ravenscar_find_new_threads (ops);
+      ravenscar_update_thread_list (ops);
       ravenscar_update_inferior_ptid ();
     }
   return inferior_ptid;
@@ -218,7 +218,7 @@ ravenscar_add_thread (struct ada_task_info *task)
 }
 
 static void
-ravenscar_find_new_threads (struct target_ops *ops)
+ravenscar_update_thread_list (struct target_ops *ops)
 {
   ada_build_task_list ();
 
@@ -368,7 +368,7 @@ init_ravenscar_thread_ops (void)
   ravenscar_ops.to_store_registers = ravenscar_store_registers;
   ravenscar_ops.to_prepare_to_store = ravenscar_prepare_to_store;
   ravenscar_ops.to_thread_alive = ravenscar_thread_alive;
-  ravenscar_ops.to_find_new_threads = ravenscar_find_new_threads;
+  ravenscar_ops.to_update_thread_list = ravenscar_update_thread_list;
   ravenscar_ops.to_pid_to_str = ravenscar_pid_to_str;
   ravenscar_ops.to_extra_thread_info = ravenscar_extra_thread_info;
   ravenscar_ops.to_get_ada_task_ptid = ravenscar_get_ada_task_ptid;
diff --git a/gdb/record-btrace.c b/gdb/record-btrace.c
index c611c7b..65d28e3 100644
--- a/gdb/record-btrace.c
+++ b/gdb/record-btrace.c
@@ -1790,18 +1790,18 @@ record_btrace_decr_pc_after_break (struct target_ops *ops,
   return ops->beneath->to_decr_pc_after_break (ops->beneath, gdbarch);
 }
 
-/* The to_find_new_threads method of target record-btrace.  */
+/* The to_update_thread_list method of target record-btrace.  */
 
 static void
-record_btrace_find_new_threads (struct target_ops *ops)
+record_btrace_update_thread_list (struct target_ops *ops)
 {
-  /* Don't expect new threads if we're replaying.  */
+  /* We don't add or remove threads during replay.  */
   if (record_btrace_is_replaying (ops))
     return;
 
   /* Forward the request.  */
   ops = ops->beneath;
-  ops->to_find_new_threads (ops);
+  ops->to_update_thread_list (ops);
 }
 
 /* The to_thread_alive method of target record-btrace.  */
@@ -1963,7 +1963,7 @@ init_record_btrace_ops (void)
   ops->to_get_tailcall_unwinder = &record_btrace_to_get_tailcall_unwinder;
   ops->to_resume = record_btrace_resume;
   ops->to_wait = record_btrace_wait;
-  ops->to_find_new_threads = record_btrace_find_new_threads;
+  ops->to_update_thread_list = record_btrace_update_thread_list;
   ops->to_thread_alive = record_btrace_thread_alive;
   ops->to_goto_record_begin = record_btrace_goto_begin;
   ops->to_goto_record_end = record_btrace_goto_end;
diff --git a/gdb/remote.c b/gdb/remote.c
index 3fa835f..cd85fd5 100644
--- a/gdb/remote.c
+++ b/gdb/remote.c
@@ -2753,16 +2753,19 @@ remote_get_threads_with_qthreadinfo (struct target_ops *ops,
   return 0;
 }
 
-/* Implement the to_find_new_threads function for the remote
+/* Implement the to_update_thread_list function for the remote
    targets.  */
 
 static void
-remote_threads_info (struct target_ops *ops)
+remote_update_thread_list (struct target_ops *ops)
 {
   struct remote_state *rs = get_remote_state ();
   struct threads_listing_context context;
   struct cleanup *old_chain;
 
+  /* Delete GDB-side threads no longer found on the target.  */
+  prune_threads ();
+
   context.items = NULL;
   old_chain = make_cleanup (clear_threads_listing_context, &context);
 
@@ -2776,7 +2779,7 @@ remote_threads_info (struct target_ops *ops)
       int i;
       struct thread_item *item;
 
-      /* Add threads we don't know about yet to our list.  */
+      /* Now add threads we don't know about yet to our list.  */
       for (i = 0;
 	   VEC_iterate (thread_item_t, context.items, i, item);
 	   ++i)
@@ -3424,7 +3427,7 @@ remote_start_remote (int from_tty, struct target_ops *target, int extended_p)
 	 controlling.  We default to adding them in the running state.
 	 The '?' query below will then tell us about which threads are
 	 stopped.  */
-      remote_threads_info (target);
+      remote_update_thread_list (target);
     }
   else if (packet_support (PACKET_QNonStop) == PACKET_ENABLE)
     {
@@ -3476,7 +3479,7 @@ remote_start_remote (int from_tty, struct target_ops *target, int extended_p)
 	}
 
       /* Fetch thread list.  */
-      target_find_new_threads ();
+      target_update_thread_list ();
 
       /* Let the stub know that we want it to return the thread.  */
       set_continue_thread (minus_one_ptid);
@@ -4446,7 +4449,7 @@ extended_remote_attach_1 (struct target_ops *target, const char *args,
       struct thread_info *thread;
 
       /* Get list of threads.  */
-      remote_threads_info (target);
+      remote_update_thread_list (target);
 
       thread = first_thread_of_process (pid);
       if (thread)
@@ -11456,7 +11459,7 @@ Specify the serial device it is connected to\n\
   remote_ops.to_pass_signals = remote_pass_signals;
   remote_ops.to_program_signals = remote_program_signals;
   remote_ops.to_thread_alive = remote_thread_alive;
-  remote_ops.to_find_new_threads = remote_threads_info;
+  remote_ops.to_update_thread_list = remote_update_thread_list;
   remote_ops.to_pid_to_str = remote_pid_to_str;
   remote_ops.to_extra_thread_info = remote_threads_extra_info;
   remote_ops.to_get_ada_task_ptid = remote_get_ada_task_ptid;
diff --git a/gdb/sol-thread.c b/gdb/sol-thread.c
index 88293c3..9993dff 100644
--- a/gdb/sol-thread.c
+++ b/gdb/sol-thread.c
@@ -624,7 +624,7 @@ check_for_thread_db (void)
       if (ptid_get_pid (ptid) != -1)
 	inferior_ptid = ptid;
 
-      target_find_new_threads ();
+      target_update_thread_list ();
       break;
 
     default:
@@ -1056,11 +1056,11 @@ solaris_pid_to_str (struct target_ops *ops, ptid_t ptid)
 }
 
 
-/* Worker bee for find_new_threads.  Callback function that gets
+/* Worker bee for update_thread_list.  Callback function that gets
    called once per user-level thread (i.e. not for LWP's).  */
 
 static int
-sol_find_new_threads_callback (const td_thrhandle_t *th, void *ignored)
+sol_update_thread_list_callback (const td_thrhandle_t *th, void *ignored)
 {
   td_err_e retval;
   td_thrinfo_t ti;
@@ -1078,15 +1078,18 @@ sol_find_new_threads_callback (const td_thrhandle_t *th, void *ignored)
 }
 
 static void
-sol_find_new_threads (struct target_ops *ops)
+sol_update_thread_list (struct target_ops *ops)
 {
   struct target_ops *beneath = find_target_beneath (ops);
 
-  /* First Find any new LWP's.  */
-  beneath->to_find_new_threads (beneath);
+  /* Delete dead threads.  */
+  prune_threads ();
+
+  /* Find any new LWP's.  */
+  beneath->to_update_thread_list (beneath);
 
   /* Then find any new user-level threads.  */
-  p_td_ta_thr_iter (main_ta, sol_find_new_threads_callback, (void *) 0,
+  p_td_ta_thr_iter (main_ta, sol_update_thread_list_callback, (void *) 0,
 		    TD_THR_ANY_STATE, TD_THR_LOWEST_PRIORITY,
 		    TD_SIGNO_MASK, TD_THR_ANY_USER_FLAGS);
 }
@@ -1200,7 +1203,7 @@ sol_get_ada_task_ptid (struct target_ops *self, long lwp, long thread)
     {
       /* The list of threads is probably not up to date.  Find any
          thread that is missing from the list, and try again.  */
-      sol_find_new_threads (&current_target);
+      sol_update_thread_list (&current_target);
       thread_info = iterate_over_threads (thread_db_find_thread_from_tid,
                                           &thread);
     }
@@ -1225,7 +1228,7 @@ init_sol_thread_ops (void)
   sol_thread_ops.to_mourn_inferior = sol_thread_mourn_inferior;
   sol_thread_ops.to_thread_alive = sol_thread_alive;
   sol_thread_ops.to_pid_to_str = solaris_pid_to_str;
-  sol_thread_ops.to_find_new_threads = sol_find_new_threads;
+  sol_thread_ops.to_update_thread_list = sol_update_thread_list;
   sol_thread_ops.to_stratum = thread_stratum;
   sol_thread_ops.to_get_ada_task_ptid = sol_get_ada_task_ptid;
   sol_thread_ops.to_magic = OPS_MAGIC;
diff --git a/gdb/target-delegates.c b/gdb/target-delegates.c
index fe989ff..9beb5ff 100644
--- a/gdb/target-delegates.c
+++ b/gdb/target-delegates.c
@@ -1302,23 +1302,23 @@ debug_thread_alive (struct target_ops *self, ptid_t arg1)
 }
 
 static void
-delegate_find_new_threads (struct target_ops *self)
+delegate_update_thread_list (struct target_ops *self)
 {
   self = self->beneath;
-  self->to_find_new_threads (self);
+  self->to_update_thread_list (self);
 }
 
 static void
-tdefault_find_new_threads (struct target_ops *self)
+tdefault_update_thread_list (struct target_ops *self)
 {
 }
 
 static void
-debug_find_new_threads (struct target_ops *self)
+debug_update_thread_list (struct target_ops *self)
 {
-  fprintf_unfiltered (gdb_stdlog, "-> %s->to_find_new_threads (...)\n", debug_target.to_shortname);
-  debug_target.to_find_new_threads (&debug_target);
-  fprintf_unfiltered (gdb_stdlog, "<- %s->to_find_new_threads (", debug_target.to_shortname);
+  fprintf_unfiltered (gdb_stdlog, "-> %s->to_update_thread_list (...)\n", debug_target.to_shortname);
+  debug_target.to_update_thread_list (&debug_target);
+  fprintf_unfiltered (gdb_stdlog, "<- %s->to_update_thread_list (", debug_target.to_shortname);
   target_debug_print_struct_target_ops_p (&debug_target);
   fputs_unfiltered (")\n", gdb_stdlog);
 }
@@ -3828,8 +3828,8 @@ install_delegators (struct target_ops *ops)
     ops->to_program_signals = delegate_program_signals;
   if (ops->to_thread_alive == NULL)
     ops->to_thread_alive = delegate_thread_alive;
-  if (ops->to_find_new_threads == NULL)
-    ops->to_find_new_threads = delegate_find_new_threads;
+  if (ops->to_update_thread_list == NULL)
+    ops->to_update_thread_list = delegate_update_thread_list;
   if (ops->to_pid_to_str == NULL)
     ops->to_pid_to_str = delegate_pid_to_str;
   if (ops->to_extra_thread_info == NULL)
@@ -4062,7 +4062,7 @@ install_dummy_methods (struct target_ops *ops)
   ops->to_pass_signals = tdefault_pass_signals;
   ops->to_program_signals = tdefault_program_signals;
   ops->to_thread_alive = tdefault_thread_alive;
-  ops->to_find_new_threads = tdefault_find_new_threads;
+  ops->to_update_thread_list = tdefault_update_thread_list;
   ops->to_pid_to_str = default_pid_to_str;
   ops->to_extra_thread_info = tdefault_extra_thread_info;
   ops->to_thread_name = tdefault_thread_name;
@@ -4205,7 +4205,7 @@ init_debug_target (struct target_ops *ops)
   ops->to_pass_signals = debug_pass_signals;
   ops->to_program_signals = debug_program_signals;
   ops->to_thread_alive = debug_thread_alive;
-  ops->to_find_new_threads = debug_find_new_threads;
+  ops->to_update_thread_list = debug_update_thread_list;
   ops->to_pid_to_str = debug_pid_to_str;
   ops->to_extra_thread_info = debug_extra_thread_info;
   ops->to_thread_name = debug_thread_name;
diff --git a/gdb/target.c b/gdb/target.c
index 34db652..fcd877c 100644
--- a/gdb/target.c
+++ b/gdb/target.c
@@ -3048,9 +3048,9 @@ target_thread_alive (ptid_t ptid)
 }
 
 void
-target_find_new_threads (void)
+target_update_thread_list (void)
 {
-  current_target.to_find_new_threads (&current_target);
+  current_target.to_update_thread_list (&current_target);
 }
 
 void
diff --git a/gdb/target.h b/gdb/target.h
index a679228..f6175a0 100644
--- a/gdb/target.h
+++ b/gdb/target.h
@@ -563,7 +563,7 @@ struct target_ops
 
     int (*to_thread_alive) (struct target_ops *, ptid_t ptid)
       TARGET_DEFAULT_RETURN (0);
-    void (*to_find_new_threads) (struct target_ops *)
+    void (*to_update_thread_list) (struct target_ops *)
       TARGET_DEFAULT_IGNORE ();
     char *(*to_pid_to_str) (struct target_ops *, ptid_t)
       TARGET_DEFAULT_FUNC (default_pid_to_str);
@@ -1568,9 +1568,9 @@ extern void target_program_signals (int nsig, unsigned char *program_signals);
 
 extern int target_thread_alive (ptid_t ptid);
 
-/* Query for new threads and add them to the thread list.  */
+/* Sync the target's threads with GDB's thread list.  */
 
-extern void target_find_new_threads (void);
+extern void target_update_thread_list (void);
 
 /* Make target stop in a continuable fashion.  (For instance, under
    Unix, this should act like SIGSTOP).  Note that this function is
diff --git a/gdb/thread.c b/gdb/thread.c
index 5a1d2e3..5c94264 100644
--- a/gdb/thread.c
+++ b/gdb/thread.c
@@ -68,7 +68,6 @@ static int thread_alive (struct thread_info *);
 static void info_threads_command (char *, int);
 static void thread_apply_command (char *, int);
 static void restore_current_thread (ptid_t);
-static void prune_threads (void);
 
 /* Data to cleanup thread array.  */
 
@@ -622,7 +621,9 @@ thread_alive (struct thread_info *tp)
   return 1;
 }
 
-static void
+/* See gdbthreads.h.  */
+
+void
 prune_threads (void)
 {
   struct thread_info *tp, *next;
@@ -1586,8 +1587,7 @@ update_threads_executing (void)
 void
 update_thread_list (void)
 {
-  prune_threads ();
-  target_find_new_threads ();
+  target_update_thread_list ();
   update_threads_executing ();
 }