FYI: Implement thread support with core files on alpha-tru64

[Joel Brobecker <brobecker at adacore dot com>]

Hello,

Thread support currently does not work with core files.  Note that,
in order to thread support to work on tru64, one need to allow GDB
to write in the core file (this is because the thread debug library
needs to write).

An obvious visible symptom of the problem is that "info threads" does
not list the various threads:

    (gdb) info threads
    * 1 <main task>  0x000003ff805c0918 in __nxm_thread_kill ()
       from /usr/shlib/libpthread.so

One other noticeable consequence is that GDB generates some warnings
when using "info tasks":

    (gdb) info tasks
    warning: Could not find thread id from THREAD = 0x3ffc01b6000

    warning: Could not find thread id from THREAD = 0x20000e2b4c0

      ID       TID P-ID Pri State                  Name
    *  1 140051000    0  30 Runnable               main_task
    *  2 14005c000    1  30 Accept or Select Term  my_t

(notice also how both tasks are marked as being the active task,
which cannot be true).

The problem is that the dec-thread module has not updated its thread list
after the core file got loaded.  In fact, the list only gets resync'ed
at the end of each target-wait.  The solution was to implement the
find_new_threads target_ops method.

gdb/ChangeLog:

        Implement thread support with core files on alpha-tru64.
        * dec-thread.c (dec_thread_find_new_threads): New function,
        extracted from resync_thread_list.
        (resync_thread_list): Add OPS parameter.  Replace extracted-out
        code by call to dec_thread_find_new_threads.
        (dec_thread_wait): Update call to resync_thread_list.
        (init_dec_thread_ops): Set dec_thread_ops.to_find_new_threads.

Tested on alpha-tru64. Checked in.

---
 gdb/dec-thread.c |   29 +++++++++++++++++++----------
 1 files changed, 19 insertions(+), 10 deletions(-)

diff --git a/gdb/dec-thread.c b/gdb/dec-thread.c
index 01191ea..4aba779 100644
--- a/gdb/dec-thread.c
+++ b/gdb/dec-thread.c
@@ -394,22 +394,15 @@ dec_thread_add_gdb_thread (struct thread_info *info, void *context)
   return 0;
 }
 
-/* Resynchronize the list of threads known by GDB with the actual
-   list of threads reported by libpthread_debug.  */
+/* Implement the find_new_thread target_ops method.  */
 
 static void
-resync_thread_list (void)
+dec_thread_find_new_threads (struct target_ops *ops)
 {
   int i;
   struct dec_thread_info *info;
-  int num_gdb_threads = 0;
-  struct thread_info **gdb_thread_list;
-  struct thread_info **next_thread_info;
 
   update_dec_thread_list ();
-
-  /* Add new threads.  */
-
   for (i = 0; VEC_iterate (dec_thread_info_s, dec_thread_list, i, info); i++)
     {
       ptid_t ptid = ptid_build_from_info (*info);
@@ -417,6 +410,21 @@ resync_thread_list (void)
       if (!in_thread_list (ptid))
         add_thread (ptid);
     }
+}
+
+/* Resynchronize the list of threads known by GDB with the actual
+   list of threads reported by libpthread_debug.  */
+
+static void
+resync_thread_list (struct target_ops *ops)
+{
+  int i;
+  int num_gdb_threads = 0;
+  struct thread_info **gdb_thread_list;
+  struct thread_info **next_thread_info;
+
+  /* Add new threads.  */
+  dec_thread_find_new_threads (ops);
 
   /* Remove threads that no longer exist.  To help with the search,
      we build an array of GDB threads, and then iterate over this
@@ -479,7 +487,7 @@ dec_thread_wait (struct target_ops *ops,
 
   /* The ptid returned by the target beneath us is the ptid of the process.
      We need to find which thread is currently active and return its ptid.  */
-  resync_thread_list ();
+  resync_thread_list (ops);
   active_ptid = get_active_ptid ();
   if (ptid_equal (active_ptid, null_ptid))
     return ptid;
@@ -708,6 +716,7 @@ 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_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;
-- 
1.6.3.3