[RFA/Ada] Implement Ada tasking support (take 2)

[Joel Brobecker <brobecker@adacore.com>]

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Following the discussions that happened on the first submissions,
here is a new version of the patch that hopefully addresses all
observations.  Just as a reference, here is the URL of the first
submission:

    http://www.sourceware.org/ml/gdb-patches/2008-09/msg00470.html

First, a big thank you to Eli and Tom who discussed the concepts and
looked at the patches. There were a couple of open questions:

  (1) The command names. The suggestion was to use an "ada" prefix to
      make it clearer that these are for Ada:

          (gdb) info ada tasks
          (gdb) ada task

      This would be breaking years of habit using "info tasks" and
      "tasks", but I don't personally mind, and it makes some kind
      of sense. I can always put some aliases in AdaCore's version.
      However, I think we ought to be consistent about this - I tried
      searching for other language-specific commands, and indeed,
      objc-lang defines "info selectors", "info classes", etc.
      I don't think that we should use that to argue that we should
      keep the old command names for Ada, particularly if we judge
      that this was a poor decision; just saying that we need to
      decide what our policy is.  Anyway, if the consensus is that
      they should be prefixed with "ada", no problem with me.

  (2) Discussion about the task-specific breakpoints. I just mentioned
      in passing this feature that is still yet to be contributed.
      I stil haven't really decided how this ought to be supported
      in the FSF tree - we have something in AdaCore's tree but it
      might not be the best way.

      Tom suggested a different syntax, which is based on using
      convenience functions in the condition field.

          break LINESPEC if $current_ada_task() == 5

      It's an interesting suggestion, and I'm not opposed. I'm just
      slightly concerned that the performance cost of evaluating
      a condition expression is higher than just a pure check
      directly coded in GDB.  It's also different from what is done
      for threads.

gdb/:
2008-09-24  Joel Brobecker  <brobecker@adacore.com>

        * target.h (struct target_ops): Add new field to_get_ada_task_ptid.
        (target_get_ada_task_ptid): New macro.
        * target.c (default_get_ada_task_ptid): New function.
        (update_current_target): Inherit field default_get_ada_task_ptid.
        (update_current_target): Make default_get_ada_task_ptid the default
        value for field to_get_ada_task_ptid.
        * ada-lang.h (struct task_control_block): Delete. Never used.
        (struct task_ptid, task_ptid_t, struct task_entry, task_list):
        Likewise.
        (struct ada_task_info): New.
        (ada_task_is_alive, ada_find_printable_frame)
        (ada_task_list_iterator_ftype, iterate_over_live_ada_tasks): Add
        declarations.
        (ada_build_task_list): Update prototype.
        (init_task_list, ada_is_exception_breakpoint): Remove prototypes.
        * ada-lang.c (ada_find_printable_frame): Make non-static.
        * ada-tasks.c: New file.
        * Makefile.in (SFILES): Add ada-tasks.c.
        (COMMON_OBS): Add ada-tasks.o.
        * linux-thread-db.c (thread_db_find_thread_from_tid)
        (thread_db_get_ada_task_ptid): New functions.
        (init_thread_db_ops): Set thread_db_ops.to_get_ada_task_ptid.

gdb/testsuite:
2008-09-24  Joel Brobecker  <brobecker@adacore.com>

        * gdb.base/completion.exp: Update expected output following
        the addition of the "info tasks" command.

gdb/doc:
2008-09-24  Joel Brobecker  <brobecker@adacore.com>

        * gdb.texinfo (Ada Tasks, Ada Tasks and Core Files): New nodes.
        (Patching): Replace incorrect usage of @samp by @kbd.

Tested on x86-linux.

-- 
Joel

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diff -r b2b21339d264 -r 46e8a5e41f74 gdb/target.h
--- a/gdb/target.h	Sun Sep 21 14:50:58 2008 -0700
+++ b/gdb/target.h	Wed Sep 24 10:15:10 2008 -0700
@@ -505,6 +505,12 @@
        was available.  */
     const struct target_desc *(*to_read_description) (struct target_ops *ops);
 
+    /* Build the PTID of the thread on which a given task is running,
+       based on LWP and THREAD.  These values are extracted from the
+       task Private_Data section of the Ada Task Control Block, and
+       their interpretation depends on the target.  */
+    ptid_t (*to_get_ada_task_ptid) (long lwp, long thread);
+
     /* Read one auxv entry from *READPTR, not reading locations >= ENDPTR.
        Return 0 if *READPTR is already at the end of the buffer.
        Return -1 if there is insufficient buffer for a whole entry.
@@ -1129,6 +1135,9 @@
 
 extern const struct target_desc *target_read_description (struct target_ops *);
 
+#define target_get_ada_task_ptid(lwp, tid) \
+     (*current_target.to_get_ada_task_ptid) (lwp,tid)
+
 /* Utility implementation of searching memory.  */
 extern int simple_search_memory (struct target_ops* ops,
                                  CORE_ADDR start_addr,
diff -r b2b21339d264 -r 46e8a5e41f74 gdb/target.c
--- a/gdb/target.c	Sun Sep 21 14:50:58 2008 -0700
+++ b/gdb/target.c	Wed Sep 24 10:15:10 2008 -0700
@@ -356,6 +356,18 @@
   tcomplain ();
 }
 
+/* A default implementation for the to_get_ada_task_ptid target method.
+
+   This function builds the PTID by using both LWP and TID as part of
+   the PTID lwp and tid elements.  The pid used is the pid of the
+   inferior_ptid.  */
+
+ptid_t
+default_get_ada_task_ptid (long lwp, long tid)
+{
+  return ptid_build (ptid_get_pid (inferior_ptid), lwp, tid);
+}
+
 /* Go through the target stack from top to bottom, copying over zero
    entries in current_target, then filling in still empty entries.  In
    effect, we are doing class inheritance through the pushed target
@@ -461,6 +473,7 @@
       INHERIT (to_make_corefile_notes, t);
       INHERIT (to_get_thread_local_address, t);
       /* Do not inherit to_read_description.  */
+      INHERIT (to_get_ada_task_ptid, t);
       /* Do not inherit to_search_memory.  */
       INHERIT (to_magic, t);
       /* Do not inherit to_memory_map.  */
@@ -626,6 +639,9 @@
 	    (int (*) (int))
 	    return_one);
   current_target.to_read_description = NULL;
+  de_fault (to_get_ada_task_ptid,
+            (ptid_t (*) (long, long))
+            default_get_ada_task_ptid);
 #undef de_fault
 
   /* Finally, position the target-stack beneath the squashed
diff -r b2b21339d264 -r 46e8a5e41f74 gdb/ada-lang.h
--- a/gdb/ada-lang.h	Sun Sep 21 14:50:58 2008 -0700
+++ b/gdb/ada-lang.h	Wed Sep 24 10:15:10 2008 -0700
@@ -196,46 +196,37 @@
 
 /* Ada task structures.  */
 
-/* Ada task control block, as defined in the GNAT runt-time library.  */
+struct ada_task_info
+{
+  /* The PTID of the thread that this task runs on.  This ptid is computed
+     in a target-dependent way from the associated Task Control Block.  */
+  ptid_t ptid;
 
-struct task_control_block
-{
-  char state;
+  /* The ID of the task.  */
+  CORE_ADDR task_id;
+
+  /* The name of the task.  */
+  char name[257];
+
+  /* The current state of the task.  */
+  int state;
+
+  /* The priority associated to the task.  */
+  int priority;
+
+  /* If non-zero, the task ID of the parent task.  */
   CORE_ADDR parent;
-  int priority;
-  char image [32];
-  int image_len;    /* This field is not always present in the ATCB.  */
-  CORE_ADDR call;
-  CORE_ADDR thread;
-  CORE_ADDR lwp;    /* This field is not always present in the ATCB.  */
 
-  /* If the task is waiting on a task entry, this field contains the
-   task_id of the other task.  */
+  /* If the task is waiting on a task entry, this field contains
+     the ID of the other task.  Zero otherwise.  */
   CORE_ADDR called_task;
+
+  /* If the task is accepting a rendezvous with another task, this field
+     contains the ID of the calling task.  Zero otherwise.  */
+  CORE_ADDR caller_task;
 };
 
-struct task_ptid
-{
-  int pid;                      /* The Process id */
-  long lwp;                     /* The Light Weight Process id */
-  long tid;                     /* The Thread id */
-};
-typedef struct task_ptid task_ptid_t;
-
-struct task_entry
-{
-  CORE_ADDR task_id;
-  struct task_control_block atcb;
-  int task_num;
-  int known_tasks_index;
-  struct task_entry *next_task;
-  task_ptid_t task_ptid;
-  int stack_per;
-};
-
-/* task entry list.  */
-extern struct task_entry *task_list;
-
+int ada_task_is_alive (struct ada_task_info *task);
 
 /* Assuming V points to an array of S objects,  make sure that it contains at
    least M objects, updating V and S as necessary. */
@@ -465,6 +456,8 @@
 						      const char **,
 						      int *, const char **);
 
+extern void ada_find_printable_frame (struct frame_info *fi);
+
 extern char *ada_breakpoint_rewrite (char *, int *);
 
 extern char *ada_main_name (void);
@@ -473,9 +466,9 @@
 
 extern int valid_task_id (int);
 
-extern void init_task_list (void);
-
-extern int ada_is_exception_breakpoint (bpstat bs);
+typedef void (ada_task_list_iterator_ftype) (struct ada_task_info *task);
+extern void iterate_over_live_ada_tasks
+  (ada_task_list_iterator_ftype *iterator);
 
 extern void ada_adjust_exception_stop (bpstat bs);
 
@@ -491,7 +484,7 @@
 
 extern void ada_reset_thread_registers (void);
 
-extern int ada_build_task_list (void);
+extern int ada_build_task_list (int warn_if_null);
 
 extern int ada_exception_catchpoint_p (struct breakpoint *b);
   
diff -r b2b21339d264 -r 46e8a5e41f74 gdb/ada-lang.c
--- a/gdb/ada-lang.c	Sun Sep 21 14:50:58 2008 -0700
+++ b/gdb/ada-lang.c	Wed Sep 24 10:15:10 2008 -0700
@@ -9852,7 +9852,7 @@
 /* Find the first frame that contains debugging information and that is not
    part of the Ada run-time, starting from FI and moving upward.  */
 
-static void
+void
 ada_find_printable_frame (struct frame_info *fi)
 {
   for (; fi != NULL; fi = get_prev_frame (fi))
diff -r b2b21339d264 -r 46e8a5e41f74 gdb/ada-tasks.c
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gdb/ada-tasks.c	Wed Sep 24 10:15:10 2008 -0700
@@ -0,0 +1,991 @@
+/* Copyright (C) 1992, 1993, 1994, 1997, 1998, 1999, 2000, 2003, 2004,
+   2005, 2007, 2008 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 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   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, see <http://www.gnu.org/licenses/>.  */
+
+#include "defs.h"
+#include "observer.h"
+#include "gdbcmd.h"
+#include "target.h"
+#include "ada-lang.h"
+#include "gdbcore.h"
+#include "inferior.h"
+#include "gdbthread.h"
+
+/* The name of the array in the GNAT runtime where the Ada Task Control
+   Block of each task is stored.  */
+#define KNOWN_TASKS_NAME "system__tasking__debug__known_tasks"
+
+/* The maximum number of tasks known to the Ada runtime */
+static const int MAX_NUMBER_OF_KNOWN_TASKS = 1000;
+
+enum task_states
+{
+  Unactivated,
+  Runnable,
+  Terminated,
+  Activator_Sleep,
+  Acceptor_Sleep,
+  Entry_Caller_Sleep,
+  Async_Select_Sleep,
+  Delay_Sleep,
+  Master_Completion_Sleep,
+  Master_Phase_2_Sleep,
+  Interrupt_Server_Idle_Sleep,
+  Interrupt_Server_Blocked_Interrupt_Sleep,
+  Timer_Server_Sleep,
+  AST_Server_Sleep,
+  Asynchronous_Hold,
+  Interrupt_Server_Blocked_On_Event_Flag
+};
+
+/* A short description corresponding to each possible task state.  */
+static char *task_states[] = {
+  _("Unactivated"),
+  _("Runnable"),
+  _("Terminated"),
+  _("Child Activation Wait"),
+  _("Accept Statement"),
+  _("Waiting on entry call"),
+  _("Async Select Wait"),
+  _("Delay Sleep"),
+  _("Child Termination Wait"),
+  _("Wait Child in Term Alt"),
+  "",
+  "",
+  "",
+  "",
+  _("Asynchronous Hold"),
+  ""
+};
+
+/* A longer description corresponding to each possible task state.  */
+static char *long_task_states[] = {
+  _("Unactivated"),
+  _("Runnable"),
+  _("Terminated"),
+  _("Waiting for child activation"),
+  _("Blocked in accept statement"),
+  _("Waiting on entry call"),
+  _("Asynchronous Selective Wait"),
+  _("Delay Sleep"),
+  _("Waiting for children termination"),
+  _("Waiting for children in terminate alternative"),
+  "",
+  "",
+  "",
+  "",
+  _("Asynchronous Hold"),
+  ""
+};
+
+/* The index of certain important fields in the Ada Task Control Block
+   record and sub-records.  */
+
+struct tcb_fieldnos
+{
+  /* Fields in record Ada_Task_Control_Block.  */
+  int common;
+  int entry_calls;
+  int atc_nesting_level;
+
+  /* Fields in record Common_ATCB.  */
+  int state;
+  int parent;
+  int priority;
+  int image;
+  int image_len;     /* This field may be missing.  */
+  int call;
+  int ll;
+
+  /* Fields in Task_Primitives.Private_Data.  */
+  int ll_thread;
+  int ll_lwp;        /* This field may be missing.  */
+
+  /* Fields in Common_ATCB.Call.all.  */
+  int call_self;
+};
+
+/* The type description for the ATCB record and subrecords, and
+   the associated tcb_fieldnos. For efficiency reasons, these are made
+   static globals so that we can compute them only once the first time
+   and reuse them later.  Set to NULL if the types haven't been computed
+   yet, or if they may be obsolete (for instance after having loaded
+   a new binary).  */
+
+static struct type *atcb_type = NULL;
+static struct type *atcb_common_type = NULL;
+static struct type *atcb_ll_type = NULL;
+static struct type *atcb_call_type = NULL;
+static struct tcb_fieldnos fieldno;
+
+/* Set to 1 when the cached address of System.Tasking.Debug.Known_Tasks
+   might be stale and so needs to be recomputed.  */
+static int ada_tasks_check_symbol_table = 1;
+
+/* The list of Ada tasks.
+ 
+   Note: To each task we associate a number that the user can use to
+   reference it - this number is printed beside each task in the tasks
+   info listing displayed by "info tasks".  This number is equal to
+   its index in the vector + 1.  Reciprocally, to compute the index
+   of a task in the vector, we need to substract 1 from its number.  */
+typedef struct ada_task_info ada_task_info_s;
+DEF_VEC_O(ada_task_info_s);
+static VEC(ada_task_info_s) *task_list = NULL;
+
+/* When non-zero, this flag indicates that the current task_list
+   is obsolete, and should be recomputed before it is accessed.  */
+static int stale_task_list_p = 1;
+
+/* Return the task number of the task whose ptid is PTID, or zero
+   if the task could not be found.  */
+
+int
+ada_get_task_number (ptid_t ptid)
+{
+  int i;
+
+  for (i=0; i < VEC_length (ada_task_info_s, task_list); i++)
+    if (ptid_equal (VEC_index (ada_task_info_s, task_list, i)->ptid, ptid))
+      return i + 1;
+
+  return 0;  /* No matching task found.  */
+}
+
+/* Return the task number of the task that matches TASK_ID, or zero
+   if the task could not be found.  */
+ 
+static int
+get_task_number_from_id (CORE_ADDR task_id)
+{
+  int i;
+
+  for (i = 0; i < VEC_length (ada_task_info_s, task_list); i++)
+    {
+      struct ada_task_info *task_info =
+        VEC_index (ada_task_info_s, task_list, i);
+
+      if (task_info->task_id == task_id)
+        return i + 1;
+    }
+
+  /* Task not found.  Return 0.  */
+  return 0;
+}
+
+/* Return non-zero if TASK_NUM is a valid task number.  */
+
+int
+valid_task_id (int task_num)
+{
+  return (task_num > 0
+          && task_num <= VEC_length (ada_task_info_s, task_list));
+}
+
+/* Return the task info associated to the Environment Task.
+   This function assumes that the inferior does in fact use tasking.  */
+
+struct ada_task_info *
+ada_get_environment_task (void)
+{
+  ada_build_task_list (0);
+  gdb_assert (VEC_length (ada_task_info_s, task_list) > 0);
+
+  /* We use a little bit of insider knowledge to determine which task
+     is the Environment Task:  We know that this task is created first,
+     and thus should always be task #1, which is at index 0 of the
+     TASK_LIST.  */
+  return (VEC_index (ada_task_info_s, task_list, 0));
+}
+
+/* Call the ITERATOR function once for each Ada task that hasn't been
+   terminated yet.  */
+
+void
+iterate_over_live_ada_tasks (ada_task_list_iterator_ftype *iterator)
+{
+  int i, nb_tasks;
+  struct ada_task_info *task;
+
+  ada_build_task_list (0);
+  nb_tasks = VEC_length (ada_task_info_s, task_list);
+
+  for (i = 0; i < nb_tasks; i++)
+    {
+      task = VEC_index (ada_task_info_s, task_list, i);
+      if (!ada_task_is_alive (task))
+        continue;
+      iterator (task);
+    }
+}
+
+/* Extract the contents of the value as a string whose length is LENGTH,
+   and store the result in DEST.  */
+
+static void
+value_as_string (char *dest, struct value *val, int length)
+{
+  memcpy (dest, value_contents (val), length);
+  dest[length] = '\0';
+}
+
+/* Extract the string image from the fat string corresponding to VAL,
+   and store it in DEST.  If the string length is greater than MAX_LEN,
+   then truncate the result to the first MAX_LEN characters of the fat
+   string.  */
+
+static void
+read_fat_string_value (char *dest, struct value *val, int max_len)
+{
+  struct value *array_val;
+  struct value *bounds_val;
+  int len;
+
+  /* The following variables are made static to avoid recomputing them
+     each time this function is called.  */
+  static int initialize_fieldnos = 1;
+  static int array_fieldno;
+  static int bounds_fieldno;
+  static int upper_bound_fieldno;
+
+  /* Get the index of the fields that we will need to read in order
+     to extract the string from the fat string.  */
+  if (initialize_fieldnos)
+    {
+      struct type *type = value_type (val);
+      struct type *bounds_type;
+
+      array_fieldno = ada_get_field_index (type, "P_ARRAY", 0);
+      bounds_fieldno = ada_get_field_index (type, "P_BOUNDS", 0);
+
+      bounds_type = TYPE_FIELD_TYPE (type, bounds_fieldno);
+      if (TYPE_CODE (bounds_type) == TYPE_CODE_PTR)
+        bounds_type = TYPE_TARGET_TYPE (bounds_type);
+      if (TYPE_CODE (bounds_type) != TYPE_CODE_STRUCT)
+        error (_("Unknown task name format. Aborting"));
+      upper_bound_fieldno = ada_get_field_index (bounds_type, "UB0", 0);
+
+      initialize_fieldnos = 0;
+    }
+
+  /* Get the size of the task image by checking the value of the bounds.
+     The lower bound is always 1, so we only need to read the upper bound.  */
+  bounds_val = value_ind (value_field (val, bounds_fieldno));
+  len = value_as_long (value_field (bounds_val, upper_bound_fieldno));
+
+  /* Make sure that we do not read more than max_len characters...  */
+  if (len > max_len)
+    len = max_len;
+
+  /* Extract LEN characters from the fat string.  */
+  array_val = value_ind (value_field (val, array_fieldno));
+  read_memory (VALUE_ADDRESS (array_val), dest, len);
+
+  /* Add the NUL character to close the string.  */
+  dest[len] = '\0';
+}
+
+/* Return the address of the Known_Tasks array maintained in
+   the Ada Runtime.  Return NULL if the array could not be found,
+   meaning that the inferior program probably does not use tasking.
+
+   In order to provide a fast response time, this function caches
+   the Known_Tasks array address after the lookup during the first
+   call. Subsequent calls will simply return this cached address.  */
+
+static CORE_ADDR
+get_known_tasks_addr (void)
+{
+  static CORE_ADDR known_tasks_addr = 0;
+
+  if (ada_tasks_check_symbol_table)
+    {
+      struct symbol *sym;
+      struct minimal_symbol *msym;
+
+      msym = lookup_minimal_symbol (KNOWN_TASKS_NAME, NULL, NULL);
+      if (msym != NULL)
+        known_tasks_addr = SYMBOL_VALUE_ADDRESS (msym);
+      else
+        {
+          if (target_lookup_symbol (KNOWN_TASKS_NAME, &known_tasks_addr) != 0)
+            return 0;
+        }
+
+      /* FIXME: brobecker 2003-03-05: Here would be a much better place
+         to attach the ada-tasks observers, instead of doing this
+         unconditionaly in _initialize_tasks. This would avoid an
+         unecessary notification when the inferior does not use tasking
+         or as long as the user does not use the ada-tasks commands.
+         Unfortunately, this is not possible for the moment: the current
+         code resets ada__tasks_check_symbol_table back to 1 whenever
+         symbols for a new program are being loaded. If we place the
+         observers intialization here, we will end up adding new observers
+         everytime we do the check for Ada tasking-related symbols
+         above. This would currently have benign effects, but is still
+         undesirable. The cleanest approach is probably to create a new
+         observer to notify us when the user is debugging a new program.
+         We would then reset ada__tasks_check_symbol_table back to 1
+         during the notification, but also detach all observers.
+         BTW: observers are probably not reentrant, so detaching during
+         a notification may not be the safest thing to do... Sigh...
+         But creating the new observer would be a good idea in any case,
+         since this allow us to make ada__tasks_check_symbol_table
+         static, which is a good bonus.  */
+      ada_tasks_check_symbol_table = 0;
+    }
+
+  return known_tasks_addr;
+}
+
+/* Get from the debugging information the type description of all types
+   related to the Ada Task Control Block that will be needed in order to
+   read the list of known tasks in the Ada runtime.  Also return the
+   associated ATCB_FIELDNOS.
+
+   Error handling:  Any data missing from the debugging info will cause
+   an error to be raised, and none of the return values to be set.
+   Users of this function can depend on the fact that all or none of the
+   return values will be set.  */
+
+static void
+get_tcb_types_info (struct type **atcb_type,
+                    struct type **atcb_common_type,
+                    struct type **atcb_ll_type,
+                    struct type **atcb_call_type,
+                    struct tcb_fieldnos *atcb_fieldnos)
+{
+  struct type *type;
+  struct type *common_type;
+  struct type *ll_type;
+  struct type *call_type;
+  struct tcb_fieldnos fieldnos;
+
+  const char *atcb_name = "system__tasking__ada_task_control_block___XVE";
+  const char *atcb_name_fixed = "system__tasking__ada_task_control_block";
+  const char *common_atcb_name = "system__tasking__common_atcb";
+  const char *private_data_name = "system__task_primitives__private_data";
+  const char *entry_call_record_name = "system__tasking__entry_call_record";
+
+  struct symbol *atcb_sym =
+    lookup_symbol (atcb_name, NULL, VAR_DOMAIN, NULL);
+  const struct symbol *common_atcb_sym =
+    lookup_symbol (common_atcb_name, NULL, VAR_DOMAIN, NULL);
+  const struct symbol *private_data_sym =
+    lookup_symbol (private_data_name, NULL, VAR_DOMAIN, NULL);
+  const struct symbol *entry_call_record_sym =
+    lookup_symbol (entry_call_record_name, NULL, VAR_DOMAIN, NULL);
+
+  if (atcb_sym == NULL || atcb_sym->type == NULL)
+    {
+      /* In Ravenscar run-time libs, the  ATCB does not have a dynamic
+         size, so the symbol name differs.  */
+      atcb_sym = lookup_symbol (atcb_name_fixed, NULL, VAR_DOMAIN, NULL);
+
+      if (atcb_sym == NULL || atcb_sym->type == NULL)
+        error (_("Cannot find Ada_Task_Control_Block type. Aborting"));
+
+      type = atcb_sym->type;
+    }
+  else
+    {
+      /* Get a static representation of the type record
+         Ada_Task_Control_Block.  */
+      type = atcb_sym->type;
+      type = ada_template_to_fixed_record_type_1 (type, NULL, 0, NULL, 0);
+    }
+
+  if (common_atcb_sym == NULL || common_atcb_sym->type == NULL)
+    error (_("Cannot find Common_ATCB type. Aborting"));
+  if (private_data_sym == NULL || private_data_sym->type == NULL)
+    error (_("Cannot find Private_Data type. Aborting"));
+  if (entry_call_record_sym == NULL || entry_call_record_sym->type == NULL)
+    error (_("Cannot find Entry_Call_Record type. Aborting"));
+
+  /* Get the type for Ada_Task_Control_Block.Common.  */
+  common_type = common_atcb_sym->type;
+
+  /* Get the type for Ada_Task_Control_Bloc.Common.Call.LL.  */
+  ll_type = private_data_sym->type;
+
+  /* Get the type for Common_ATCB.Call.all.  */
+  call_type = entry_call_record_sym->type;
+
+  /* Get the field indices.  */
+  fieldnos.common = ada_get_field_index (type, "common", 0);
+  fieldnos.entry_calls = ada_get_field_index (type, "entry_calls", 1);
+  fieldnos.atc_nesting_level =
+    ada_get_field_index (type, "atc_nesting_level", 1);
+  fieldnos.state = ada_get_field_index (common_type, "state", 0);
+  fieldnos.parent = ada_get_field_index (common_type, "parent", 1);
+  fieldnos.priority = ada_get_field_index (common_type, "base_priority", 0);
+  fieldnos.image = ada_get_field_index (common_type, "task_image", 1);
+  fieldnos.image_len = ada_get_field_index (common_type, "task_image_len", 1);
+  fieldnos.call = ada_get_field_index (common_type, "call", 1);
+  fieldnos.ll = ada_get_field_index (common_type, "ll", 0);
+  fieldnos.ll_thread = ada_get_field_index (ll_type, "thread", 0);
+  fieldnos.ll_lwp = ada_get_field_index (ll_type, "lwp", 1);
+  fieldnos.call_self = ada_get_field_index (call_type, "self", 0);
+
+  /* On certain platforms such as x86-windows, the "lwp" field has been
+     named "thread_id".  This field will likely be renamed in the future,
+     but we need to support both possibilities to avoid an unnecessary
+     dependency on a recent compiler.  We therefore try locating the
+     "thread_id" field in place of the "lwp" field if we did not find
+     the latter.  */
+  if (fieldnos.ll_lwp < 0)
+    fieldnos.ll_lwp = ada_get_field_index (ll_type, "thread_id", 1);
+
+  /* Set all the out parameters all at once, now that we are certain
+     that there are no potential error() anymore.  */
+  *atcb_type = type;
+  *atcb_common_type = common_type;
+  *atcb_ll_type = ll_type;
+  *atcb_call_type = call_type;
+  *atcb_fieldnos = fieldnos;
+}
+
+/* Build the PTID of the task from its COMMON_VALUE, which is the "Common"
+   component of its ATCB record.  This PTID needs to match the PTID used
+   by the thread layer.  */
+
+static ptid_t
+ptid_from_atcb_common (struct value *common_value)
+{
+  long thread = 0;
+  CORE_ADDR lwp = 0;
+  struct value *ll_value;
+  ptid_t ptid;
+
+  ll_value = value_field (common_value, fieldno.ll);
+
+  if (fieldno.ll_lwp >= 0)
+    lwp = value_as_address (value_field (ll_value, fieldno.ll_lwp));
+  thread = value_as_long (value_field (ll_value, fieldno.ll_thread));
+
+  ptid = target_get_ada_task_ptid (lwp, thread);
+
+  return ptid;
+}
+
+/* Read the ATCB data of a given task given its TASK_ID (which is in practice
+   the address of its assocated ATCB record), and store the result inside
+   TASK_INFO.  */
+
+static void
+read_atcb (CORE_ADDR task_id, struct ada_task_info *task_info)
+{
+  struct value *tcb_value;
+  struct value *common_value;
+  struct value *atc_nesting_level_value;
+  struct value *entry_calls_value;
+  struct value *entry_calls_value_element;
+  int called_task_fieldno = -1;
+  const char ravenscar_task_name[] = "Ravenscar task";
+
+  if (atcb_type == NULL)
+    get_tcb_types_info (&atcb_type, &atcb_common_type, &atcb_ll_type,
+                        &atcb_call_type, &fieldno);
+
+  tcb_value = value_from_contents_and_address (atcb_type, NULL, task_id);
+  common_value = value_field (tcb_value, fieldno.common);
+
+  /* Fill in the task_id.  */
+
+  task_info->task_id = task_id;
+
+  /* Compute the name of the task.
+
+     Depending on the GNAT version used, the task image is either a fat
+     string, or a thin array of characters.  Older versions of GNAT used
+     to use fat strings, and therefore did not need an extra field in
+     the ATCB to store the string length. For efficiency reasons, newer
+     versions of GNAT replaced the fat string by a static buffer, but this
+     also required the addition of a new field named "Image_Len" containing
+     the length of the task name. The method used to extract the task name
+     is selected depending on the existence of this field.
+
+     In some run-time libs (e.g. Ravenscar), the name is not in the ATCB;
+     we may want to get it from the first user frame of the stack. For now,
+     we just give a dummy name.  */
+
+  if (fieldno.image_len == -1)
+    {
+      if (fieldno.image >= 0)
+        read_fat_string_value (task_info->name,
+                               value_field (common_value, fieldno.image),
+                               sizeof (task_info->name) - 1);
+      else
+        strcpy (task_info->name, ravenscar_task_name);
+    }
+  else
+    {
+      int len = value_as_long (value_field (common_value, fieldno.image_len));
+
+      value_as_string (task_info->name,
+                       value_field (common_value, fieldno.image), len);
+    }
+
+  /* Compute the task state and priority.  */
+
+  task_info->state = value_as_long (value_field (common_value, fieldno.state));
+  task_info->priority =
+    value_as_long (value_field (common_value, fieldno.priority));
+
+  /* If the ATCB contains some information about the parent task,
+     then compute it as well.  Otherwise, zero.  */
+
+  if (fieldno.parent >= 0)
+    task_info->parent =
+      value_as_address (value_field (common_value, fieldno.parent));
+  else
+    task_info->parent = 0;
+  
+
+  /* If the ATCB contains some information about entry calls, then
+     compute the "called_task" as well.  Otherwise, zero.  */
+
+  if (fieldno.atc_nesting_level > 0 && fieldno.entry_calls > 0) 
+    {
+      /* Let My_ATCB be the Ada task control block of a task calling the
+         entry of another task; then the Task_Id of the called task is
+         in My_ATCB.Entry_Calls (My_ATCB.ATC_Nesting_Level).Called_Task.  */
+      atc_nesting_level_value = value_field (tcb_value,
+                                             fieldno.atc_nesting_level);
+      entry_calls_value =
+        ada_coerce_to_simple_array_ptr (value_field (tcb_value,
+                                                     fieldno.entry_calls));
+      entry_calls_value_element =
+        value_subscript (entry_calls_value, atc_nesting_level_value);
+      called_task_fieldno =
+        ada_get_field_index (value_type (entry_calls_value_element),
+                             "called_task", 0);
+      task_info->called_task =
+        value_as_address (value_field (entry_calls_value_element,
+                                       called_task_fieldno));
+    }
+  else
+    {
+      task_info->called_task = 0;
+    }
+
+  /* If the ATCB cotnains some information about RV callers,
+     then compute the "caller_task".  Otherwise, zero.  */
+
+  task_info->caller_task = 0;
+  if (fieldno.call >= 0)
+    {
+      /* Get the ID of the caller task from Common_ATCB.Call.all.Self.
+         If Common_ATCB.Call is null, then there is no caller.  */
+      const CORE_ADDR call =
+        value_as_address (value_field (common_value, fieldno.call));
+      struct value *call_val;
+
+      if (call != 0)
+        {
+          call_val =
+            value_from_contents_and_address (atcb_call_type, NULL, call);
+          task_info->caller_task =
+            value_as_address (value_field (call_val, fieldno.call_self));
+        }
+    }
+
+  /* And finally, compute the task ptid.  */
+
+  if (ada_task_is_alive (task_info))
+    task_info->ptid = ptid_from_atcb_common (common_value);
+  else
+    task_info->ptid = null_ptid;
+}
+
+/* Read the ATCB info of the given task (identified by TASK_ID), and
+   add the result to the TASK_LIST.  */
+
+static void
+add_ada_task (CORE_ADDR task_id)
+{
+  struct ada_task_info task_info;
+
+  read_atcb (task_id, &task_info);
+  VEC_safe_push (ada_task_info_s, task_list, &task_info);
+}
+
+/* Read the Known_Tasks array from the inferior memory, and store
+   it in TASK_LIST.  Return non-zero upon success.  */
+
+static int
+read_known_tasks_array (void)
+{
+  const int target_ptr_byte =
+    gdbarch_ptr_bit (current_gdbarch) / TARGET_CHAR_BIT;
+  const CORE_ADDR known_tasks_addr = get_known_tasks_addr ();
+  const int known_tasks_size = target_ptr_byte * MAX_NUMBER_OF_KNOWN_TASKS;
+  gdb_byte *known_tasks = alloca (known_tasks_size);
+  int i;
+
+  /* Step 1: Clear the current list, if necessary.  */
+  VEC_truncate (ada_task_info_s, task_list, 0);
+
+  /* If the application does not use task, then no more needs to be done.
+     It is important to have the task list cleared (see above) before we
+     return, as we don't want a stale task list to be used...  This can
+     happen for instance when debugging a non-multitasking program after
+     having debugged a multitasking one.  */
+  if (known_tasks_addr == 0)
+    return 0;
+
+  /* Step 2: Build a new list by reading the ATCBs from the Known_Tasks
+     array in the Ada runtime.  */
+  read_memory (known_tasks_addr, known_tasks, known_tasks_size);
+  for (i = 0; i < MAX_NUMBER_OF_KNOWN_TASKS; i++)
+    {
+      struct type *data_ptr_type =
+        builtin_type (current_gdbarch)->builtin_data_ptr;
+      CORE_ADDR task_id =
+        extract_typed_address (known_tasks + i * target_ptr_byte,
+			       data_ptr_type);
+
+      if (task_id != 0)
+        add_ada_task (task_id);
+    }
+
+  /* Step 3: Unset stale_task_list_p, to avoid re-reading the Known_Tasks
+     array unless needed.  Then report a success.  */
+  stale_task_list_p = 0;
+
+  return 1;
+}
+
+/* Builds the task_list by reading the Known_Tasks array from
+   the inferior.  Prints an appropriate message and returns non-zero
+   if it failed to build this list.  */
+
+int
+ada_build_task_list (int warn_if_null)
+{
+  if (!target_has_stack)
+    error (_("Cannot inspect Ada tasks when program is not running"));
+
+  if (stale_task_list_p)
+    read_known_tasks_array ();
+
+  if (task_list == NULL)
+    {
+      if (warn_if_null)
+        printf_filtered (_("Your application does not use any Ada tasks.\n"));
+      return 0;
+    }
+
+  return 1;
+}
+
+/* Return non-zero iff the task STATE corresponds to a non-terminated
+   task state.  */
+
+int
+ada_task_is_alive (struct ada_task_info *task_info)
+{
+  return (task_info->state != Terminated);
+}
+
+/* Print a one-line description of the task whose number is TASKNO.
+   The formatting should fit the "info tasks" array.  */
+
+static void
+short_task_info (int taskno)
+{
+  const struct ada_task_info *const task_info =
+    VEC_index (ada_task_info_s, task_list, taskno - 1);
+  int active_task_p;
+
+  gdb_assert (task_info != NULL);
+
+  /* Print a star if this task is the current task (or the task currently
+     selected).  */
+
+  active_task_p = ptid_equal (task_info->ptid, inferior_ptid);
+  if (active_task_p)
+    printf_filtered ("*");
+  else
+    printf_filtered (" ");
+
+  /* Print the task number.  */
+  printf_filtered ("%3d", taskno);
+
+  /* Print the Task ID.  */
+  printf_filtered (" %9lx", (long) task_info->task_id);
+
+  /* Print the Task ID of the task parent.  */
+  printf_filtered (" %4d", get_task_number_from_id (task_info->parent));
+
+  /* Print the base priority of the task.  */
+  printf_filtered (" %3d", task_info->priority);
+
+  /* Print the task current state.  */
+  if (task_info->caller_task)
+    printf_filtered (_(" Accepting RV with %-4d"),
+                     get_task_number_from_id (task_info->caller_task));
+  else if (task_info->state == Entry_Caller_Sleep && task_info->called_task)
+    printf_filtered (_(" Waiting on RV with %-3d"),
+                     get_task_number_from_id (task_info->called_task));
+  else if (task_info->state == Runnable && active_task_p)
+    /* Replace "Runnable" by "Running" since this is the active task.  */
+    printf_filtered (" %-22s", "Running");
+  else
+    printf_filtered (" %-22s", task_states[task_info->state]);
+
+  /* Finally, print the task name.  */
+  if (task_info->name[0] != '\0')
+    printf_filtered (" %s\n", task_info->name);
+  else
+    printf_filtered (_(" <no name>\n"));
+}
+
+/* Print a list containing a short description of all Ada tasks.  */
+/* FIXME: Shouldn't we be using ui_out??? */
+
+static void
+info_tasks (int from_tty)
+{
+  int taskno;
+  const int nb_tasks = VEC_length (ada_task_info_s, task_list);
+
+  printf_filtered (_("  ID       TID P-ID Pri State                  Name\n"));
+  
+  for (taskno = 1; taskno <= nb_tasks; taskno++)
+    short_task_info (taskno);
+}
+
+/* Print a detailed description of the Ada task whose ID is TASKNO_STR.  */
+
+static void
+info_task (char *taskno_str, int from_tty)
+{
+  const int taskno = value_as_long (parse_and_eval (taskno_str));
+  struct ada_task_info *task_info;
+  int parent_taskno = 0;
+
+  if (taskno <= 0 || taskno > VEC_length (ada_task_info_s, task_list))
+    error (_("Task ID %d not known.  Use the \"info tasks\" command to\n"
+             "see the IDs of currently known tasks"), taskno);
+  task_info = VEC_index (ada_task_info_s, task_list, taskno - 1);
+
+  /* Print the Ada task ID.  */
+  printf_filtered (_("Ada Task: %s\n"), paddr_nz (task_info->task_id));
+
+  /* Print the name of the task.  */
+  if (task_info->name[0] != '\0')
+    printf_filtered (_("Name: %s\n"), task_info->name);
+  else
+    printf_filtered (_("<no name>\n"));
+
+  /* Print the TID and LWP.  */
+  printf_filtered (_("Thread: %#lx\n"), ptid_get_tid (task_info->ptid));
+  printf_filtered (_("LWP: %#lx\n"), ptid_get_lwp (task_info->ptid));
+
+  /* Print who is the parent (if any).  */
+  if (task_info->parent != 0)
+    parent_taskno = get_task_number_from_id (task_info->parent);
+  if (parent_taskno)
+    {
+      struct ada_task_info *parent =
+        VEC_index (ada_task_info_s, task_list, parent_taskno - 1);
+
+      printf_filtered (_("Parent: %d"), parent_taskno);
+      if (parent->name[0] != '\0')
+        printf_filtered (" (%s)", parent->name);
+      printf_filtered ("\n");
+    }
+  else
+    printf_filtered (_("No parent\n"));
+
+  /* Print the base priority.  */
+  printf_filtered (_("Base Priority: %d\n"), task_info->priority);
+
+  /* print the task current state.  */
+  {
+    int target_taskno = 0;
+
+    if (task_info->caller_task)
+      {
+        target_taskno = get_task_number_from_id (task_info->caller_task);
+        printf_filtered (_("State: Accepting rendezvous with %d"),
+                         target_taskno);
+      }
+    else if (task_info->state == Entry_Caller_Sleep && task_info->called_task)
+      {
+        target_taskno = get_task_number_from_id (task_info->called_task);
+        printf_filtered (_("State: Waiting on task %d's entry"),
+                         target_taskno);
+      }
+    else
+      printf_filtered ("State: %s", long_task_states[task_info->state]);
+
+    if (target_taskno)
+      {
+        struct ada_task_info *target_task_info =
+          VEC_index (ada_task_info_s, task_list, target_taskno - 1);
+
+        if (target_task_info->name[0] != '\0')
+          printf_filtered (" (%s)", target_task_info->name);
+      }
+
+    printf_filtered ("\n");
+  }
+}
+
+/* If ARG is empty or null, then print a list of all Ada tasks.
+   Otherwise, print detailed information about the task whose ID
+   is ARG.
+   
+   Does nothing if the program doesn't use Ada tasking.  */
+
+static void
+info_tasks_command (char *arg, int from_tty)
+{
+  const int task_list_built = ada_build_task_list (1);
+
+  if (!task_list_built)
+    return;
+
+  if (arg == NULL || *arg == '\0')
+    info_tasks (from_tty);
+  else
+    info_task (arg, from_tty);
+}
+
+/* Print a message telling the user id of the current task.
+   This function assumes that tasking is in use in the inferior.  */
+
+static void
+display_current_task_id (void)
+{
+  const int current_task = ada_get_task_number (inferior_ptid);
+
+  if (current_task == 0)
+    printf_filtered (_("[Current task is unknown]\n"));
+  else
+    printf_filtered (_("[Current task is %d]\n"), current_task);
+}
+
+/* Parse and evaluate TIDSTR into a task id, and try to switch to
+   that task.  Print an error message if the task switch failed.  */
+
+static void
+task_command_1 (char *taskno_str, int from_tty)
+{
+  const int taskno = value_as_long (parse_and_eval (taskno_str));
+  struct ada_task_info *task_info;
+
+  if (taskno <= 0 || taskno > VEC_length (ada_task_info_s, task_list))
+    error (_("Task ID %d not known.  Use the \"info tasks\" command to\n"
+             "see the IDs of currently known tasks"), taskno);
+  task_info = VEC_index (ada_task_info_s, task_list, taskno - 1);
+
+  if (!ada_task_is_alive (task_info))
+    error (_("Cannot switch to task %d: Task is no longer running"), taskno);
+   
+  switch_to_thread (task_info->ptid);
+  ada_find_printable_frame (get_selected_frame (NULL));
+  printf_filtered (_("[Switching to task %d]\n"), taskno);
+  print_stack_frame (get_selected_frame (NULL),
+                     frame_relative_level (get_selected_frame (NULL)), 1);
+}
+
+
+/* Print the ID of the current task if TASKNO_STR is empty or NULL.
+   Otherwise, switch to the task indicated by TASKNO_STR.  */
+
+static void
+task_command (char *taskno_str, int from_tty)
+{
+  const int task_list_built = ada_build_task_list (1);
+
+  if (!task_list_built)
+    return;
+
+  if (taskno_str == NULL || taskno_str[0] == '\0')
+    display_current_task_id ();
+  else
+    {
+      /* Task switching in core files doesn't work, either because:
+           1. Thread support is not implemented with core files
+           2. Thread support is implemented, but the thread IDs created
+              after having read the core file are not the same as the ones
+              that were used during the program life, before the crash.
+              As a consequence, there is no longer a way for the debugger
+              to find the associated thead ID of any given Ada task.
+         So, instead of attempting a task switch without giving the user
+         any clue as to what might have happened, just error-out with
+         a message explaining that this feature is not supported.  */
+      if (!target_has_execution)
+        error (_("\
+Task switching not supported when debugging from core files\n\
+(use thread support instead)"));
+      task_command_1 (taskno_str, from_tty);
+    }
+}
+
+/* Indicate that the task list may have changed, so invalidate the cache.  */
+
+void
+ada_task_list_changed (void)
+{
+  stale_task_list_p = 1;  
+}
+
+/* The 'normal_stop' observer notification callback.  */
+
+static void
+ada_normal_stop_observer (struct bpstats *unused_args)
+{
+  /* The inferior has been resumed, and just stopped. This means that
+     our task_list needs to be recomputed before it can be used again.  */
+  ada_task_list_changed ();
+}
+
+/* A routine to be called when the objfiles have changed.  */
+
+void
+ada_new_objfile_observer (struct objfile *objfile)
+{
+  /* Invalidate all cached data that were extracted from an objfile.  */
+
+  atcb_type = NULL;
+  atcb_common_type = NULL;
+  atcb_ll_type = NULL;
+  atcb_call_type = NULL;
+
+  ada_tasks_check_symbol_table = 1;
+}
+
+void
+_initialize_tasks (void)
+{
+  /* Attach various observers.  */
+  observer_attach_normal_stop (ada_normal_stop_observer);
+  observer_attach_new_objfile (ada_new_objfile_observer);
+
+  /* Some new commands provided by this module.  */
+  add_info ("tasks", info_tasks_command,
+            _("Provide information about all known Ada tasks"));
+  add_cmd ("task", class_run, task_command,
+           _("Use this command to switch between Ada tasks.\n\
+Without argument, this command simply prints the current task ID"),
+           &cmdlist);
+}
+
diff -r b2b21339d264 -r 46e8a5e41f74 gdb/Makefile.in
--- a/gdb/Makefile.in	Sun Sep 21 14:50:58 2008 -0700
+++ b/gdb/Makefile.in	Wed Sep 24 10:15:10 2008 -0700
@@ -609,7 +609,7 @@
 # Links made at configuration time should not be specified here, since
 # SFILES is used in building the distribution archive.
 
-SFILES = ada-exp.y ada-lang.c ada-typeprint.c ada-valprint.c  \
+SFILES = ada-exp.y ada-lang.c ada-typeprint.c ada-valprint.c ada-tasks.c \
 	addrmap.c \
 	auxv.c ax-general.c ax-gdb.c \
 	bcache.c \
@@ -782,6 +782,7 @@
 	dwarf2read.o mipsread.o stabsread.o corefile.o \
 	dwarf2expr.o dwarf2loc.o dwarf2-frame.o \
 	ada-lang.o c-lang.o f-lang.o objc-lang.o \
+	ada-tasks.o \
 	ui-out.o cli-out.o \
 	varobj.o vec.o wrapper.o \
 	jv-lang.o jv-valprint.o jv-typeprint.o \
diff -r b2b21339d264 -r 46e8a5e41f74 gdb/linux-thread-db.c
--- a/gdb/linux-thread-db.c	Sun Sep 21 14:50:58 2008 -0700
+++ b/gdb/linux-thread-db.c	Wed Sep 24 10:15:10 2008 -0700
@@ -1143,6 +1143,35 @@
 	         _("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 ();
+  thread_info = iterate_over_threads (thread_db_find_thread_from_tid, &thread);
+
+  gdb_assert (thread_info != NULL);
+
+  return (thread_info->ptid);
+}
+
 static void
 init_thread_db_ops (void)
 {
@@ -1163,6 +1192,7 @@
   thread_db_ops.to_is_async_p = thread_db_is_async_p;
   thread_db_ops.to_async = thread_db_async;
   thread_db_ops.to_async_mask = thread_db_async_mask;
+  thread_db_ops.to_get_ada_task_ptid = thread_db_get_ada_task_ptid;
   thread_db_ops.to_magic = OPS_MAGIC;
 }
 
diff -r b2b21339d264 -r 46e8a5e41f74 gdb/testsuite/gdb.base/completion.exp
--- a/gdb/testsuite/gdb.base/completion.exp	Sun Sep 21 14:50:58 2008 -0700
+++ b/gdb/testsuite/gdb.base/completion.exp	Wed Sep 24 10:15:10 2008 -0700
@@ -223,7 +223,7 @@
         -re "^info t foo\\\x07$"\
             { send_gdb "\n"
               gdb_expect {
-                      -re "Ambiguous info command \"t foo\": target, terminal, threads, tp, tracepoints, types\\..*$gdb_prompt $"\
+                      -re "Ambiguous info command \"t foo\": target, tasks, terminal, threads, tp, tracepoints, types\\..*$gdb_prompt $"\
                                         { pass "complete 'info t foo'"}
                       -re ".*$gdb_prompt $" { fail "complete 'info t foo'"}
                       timeout           {fail "(timeout) complete 'info t foo'"}
@@ -239,7 +239,7 @@
         -re "^info t\\\x07$"\
             { send_gdb "\n"
               gdb_expect {
-                      -re "Ambiguous info command \"t\": target, terminal, threads, tp, tracepoints, types\\..
+                      -re "Ambiguous info command \"t\": target, tasks, terminal, threads, tp, tracepoints, types\\..
 *$gdb_prompt $"\
                                         { pass "complete 'info t'"}
                       -re ".*$gdb_prompt $" { fail "complete 'info t'"}
@@ -257,7 +257,7 @@
         -re "^info t \\\x07$"\
             { send_gdb "\n"
               gdb_expect {
-                      -re "Ambiguous info command \"t \": target, terminal, threads, tp, tracepoints, types\\..
+                      -re "Ambiguous info command \"t \": target, tasks, terminal, threads, tp, tracepoints, types\\..
 *$gdb_prompt $"\
                                         { pass "complete 'info t '"}
                       -re ".*$gdb_prompt $" { fail "complete 'info t '"}

[-- Attachment #3: doc-ada-tasks.diff --]
[-- Type: text/plain, Size: 6600 bytes --]

diff -r b2b21339d264 -r 46e8a5e41f74 gdb/doc/gdb.texinfo
--- a/gdb/doc/gdb.texinfo	Sun Sep 21 14:50:58 2008 -0700
+++ b/gdb/doc/gdb.texinfo	Wed Sep 24 10:15:10 2008 -0700
@@ -11042,6 +11042,8 @@
 * Omissions from Ada::          Restrictions on the Ada expression syntax.
 * Additions to Ada::            Extensions of the Ada expression syntax.
 * Stopping Before Main Program:: Debugging the program during elaboration.
+* Ada Tasks::                   Listing and setting breakpoints in tasks.
+* Ada Tasks and Core Files::    Tasking Support when Debugging Core Files
 * Ada Glitches::                Known peculiarities of Ada mode.
 @end menu
 
@@ -11361,6 +11363,187 @@
 @code{adainit}.  To run your program up to the beginning of
 elaboration, simply use the following two commands:
 @code{tbreak adainit} and @code{run}.
+
+@node Ada Tasks
+@subsubsection Extensions for Ada Tasks
+@cindex Ada, tasking
+
+Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
+@value{GDBN} provides the following task-related commands:
+
+@table @code
+@kindex info tasks
+@item info tasks
+This command shows a list of current Ada tasks, as in the following example:
+
+
+@smallexample
+@iftex
+@leftskip=0.5cm
+@end iftex
+(@value{GDBP}) info tasks
+  ID       TID P-ID Pri State                 Name
+   1   8088000   0   15 Child Activation Wait main_task
+   2   80a4000   1   15 Accept Statement      b
+   3   809a800   1   15 Child Activation Wait a
+*  4   80ae800   3   15 Running               c
+
+@end smallexample
+
+@noindent
+In this listing, the asterisk before the last task indicates it to be the
+task currently being inspected.
+
+@table @asis
+@item ID
+Represents @value{GDBN}'s internal task number.
+
+@item TID
+The Ada task ID.
+
+@item P-ID
+The parent's task ID (@value{GDBN}'s internal task number).
+
+@item Pri
+The base priority of the task.
+
+@item State
+Current state of the task.
+
+@table @code
+@item Unactivated
+The task has been created but has not been activated.  It cannot be
+executing.
+
+@item Running
+The task currently running.
+
+@item Runnable
+The task is not blocked for any reason known to Ada.  (It may be waiting
+for a mutex, though.) It is conceptually "executing" in normal mode.
+
+@item Terminated
+The task is terminated, in the sense of ARM 9.3 (5).  Any dependents
+that were waiting on terminate alternatives have been awakened and have
+terminated themselves.
+
+@item Child Activation Wait
+The task is waiting for created tasks to complete activation.
+
+@item Accept Statement
+The task is waiting on an accept or selective wait statement.
+
+@item Waiting on entry call
+The task is waiting on an entry call.
+
+@item Async Select Wait
+The task is waiting to start the abortable part of an asynchronous
+select statement.
+
+@item Delay Sleep
+The task is waiting on a select statement with only a delay
+alternative open.
+
+@item Child Termination Wait
+The task is sleeping having completed a master within itself, and is
+waiting for the tasks dependent on that master to become terminated or
+waiting on a terminate Phase.
+
+@item Wait Child in Term Alt
+The task is sleeping waiting for tasks on terminate alternatives to
+finish terminating.
+
+@item Accepting RV with @var{taskno}
+The task is accepting a rendez-vous with the task @var{taskno}.
+@end table
+
+@item Name
+Name of the task in the program.
+
+@end table
+
+@kindex info task @var{taskno}
+@item info task @var{taskno}
+This command shows detailled informations on the specified task, as in
+the following example:
+@smallexample
+@iftex
+@leftskip=0.5cm
+@end iftex
+(@value{GDBP}) info tasks
+  ID       TID P-ID Pri State                  Name
+   1   8077880    0  15 Child Activation Wait  main_task
+*  2   807c468    1  15 Running                task_1
+(@value{GDBP}) info task 2
+Ada Task: 0x807c468
+Name: task_1
+Thread: 0x807f378
+Parent: 1 (main_task)
+Base Priority: 15
+State: Runnable
+@end smallexample
+
+@item task
+@kindex task@r{ (Ada)}
+@cindex current Ada task ID
+This command prints the ID of the current task.
+
+@smallexample
+@iftex
+@leftskip=0.5cm
+@end iftex
+(@value{GDBP}) info tasks
+  ID       TID P-ID Pri State                  Name
+   1   8077870    0  15 Child Activation Wait  main_task
+*  2   807c458    1  15 Running                t
+(@value{GDBP}) task
+[Current task is 2]
+@end smallexample
+
+@item task @var{taskno}
+@cindex Ada task switching
+This command is like the @code{thread @var{threadno}}
+command (@pxref{Threads}).  It switches the context of debugging
+from the current task to the given task.
+
+@smallexample
+@iftex
+@leftskip=0.5cm
+@end iftex
+(@value{GDBP}) info tasks
+  ID       TID P-ID Pri State                  Name
+   1   8077870    0  15 Child Activation Wait  main_task
+*  2   807c458    1  15 Running                t
+(@value{GDBP}) task 1
+[Switching to task 1]
+#0  0x8067726 in pthread_cond_wait ()
+(@value{GDBP}) bt
+#0  0x8067726 in pthread_cond_wait ()
+#1  0x8056714 in system.os_interface.pthread_cond_wait ()
+#2  0x805cb63 in system.task_primitives.operations.sleep ()
+#3  0x806153e in system.tasking.stages.activate_tasks ()
+#4  0x804aacc in un () at un.adb:5
+@end smallexample
+
+@end table
+
+@node Ada Tasks and Core Files
+@subsubsection Tasking Support when Debugging Core Files
+@cindex Ada tasking and core file debugging
+
+When inspecting a core file, as opposed to debugging a live program,
+tasking support may be limited or even unavailable, depending on
+the platform being used.
+For instance, on x86-linux, the list of tasks is available, but task
+switching is not supported.  On Tru64, however, task switching will work
+as usual.
+
+On certain platforms, including Tru64, the debugger needs to perform some
+memory writes in order to provide Ada tasking support.  When inspecting
+a core file, this means that the core file must be opened with read-write
+privileges, using the command @samp{"set write on"} (@pxref{Patching}).
+Under these circumstances, you should make a backup copy of the core
+file before inspecting it with @value{GDBN}.
 
 @node Ada Glitches
 @subsubsection Known Peculiarities of Ada Mode
@@ -12166,7 +12349,7 @@
 @item set write on
 @itemx set write off
 If you specify @samp{set write on}, @value{GDBN} opens executable and
-core files for both reading and writing; if you specify @samp{set write
+core files for both reading and writing; if you specify @kbd{set write
 off} (the default), @value{GDBN} opens them read-only.
 
 If you have already loaded a file, you must load it again (using the