[v2] Remove support for thread events without PTRACE_EVENT_CLONE in GDB.

  Before, on systems that did not support PTRACE_EVENT_CLONE, both GDB and
GDBServer coordinated with libthread_db.so to insert breakpoints at magic
locations in libpthread.so, in order to break at thread creation and
thread death.

Support for thread events was removed from GDBServer as patch:
https://sourceware.org/ml/gdb-patches/2015-11/msg00466.html

This patch removes support for thread events in GDB.

No regressions found on Ubuntu 14.04 x86_64.

gdb/ChangeLog:
	* breakpoint.c (remove_thread_event_breakpoints): Remove.
	* breakpoint.h (remove_thread_event_breakpoints): Remove
	declaration.
	* linux-nat.c (in_pid_list_p): Remove.
	(lin_lwp_attach_lwp): Remove.
	* linux-nat.h (lin_lwp_attach_lwp): Remove declaration.
	* linux-thread-db.c (thread_db_use_events): Remove.
	(struct thread_db_info) <td_create_bp_addr>: Remove.
	<td_death_bp_addr>: Likewise.
	<td_ta_event_addr_p>: Likewise.
	<td_ta_set_event_p>: Likewise.
	<td_ta_clear_event_p>: Likewise.
	<td_ta_event_getmsg_p>: Likewise.
	<td_thr_event_enable_p>: Likewise.
	(attach_thread): Likewise.
	(detach_thread): Likewise.
	(have_threads_callback): Likewise.
	(have_threads): Likewise.
	(enable_thread_event): Likewise.
	(enable_thread_event_reporting): Likewise.
	(try_thread_db_load_1): Remove td_ta_event_addr, td_ta_set_event,
	td_ta_clear_event, td_ta_event_getmsg, td_thr_event_enable
	initializations.
	(try_thread_db_load_1): Remove enable_thread_event_reporting call.
	(disable_thread_event_reporting): Remove.
	(record_thread): Adapt to thread_db_use_event removal.
	(detach_thread): Remove.
	(thread_db_detach): Adapt to thread_db_use_event removal.
	(check_event): Remove.
	(thread_db_wait): Adapt to thread events support removal.
	(thread_db_mourn_inferior): Likewise.
	(find_new_threads_callback): Likewise.
	(find_new_threads_once): Likewise.
	(thread_db_update_thread_list): Likewise.
---
 gdb/breakpoint.c      |  11 --
 gdb/breakpoint.h      |   2 -
 gdb/linux-nat.c       | 144 -----------------
 gdb/linux-nat.h       |   2 -
 gdb/linux-thread-db.c | 437 ++------------------------------------------------
 5 files changed, 9 insertions(+), 587 deletions(-)
  

On 12/10/2015 03:22 PM, Antoine Tremblay wrote:
> Before, on systems that did not support PTRACE_EVENT_CLONE, both GDB and
> GDBServer coordinated with libthread_db.so to insert breakpoints at magic
> locations in libpthread.so, in order to break at thread creation and
> thread death.
> 
> Support for thread events was removed from GDBServer as patch:
> https://sourceware.org/ml/gdb-patches/2015-11/msg00466.html
> 
> This patch removes support for thread events in GDB.
> 
> No regressions found on Ubuntu 14.04 x86_64.
> 

LGTM.

Thanks,
Pedro Alves
  

On 12/10/2015 10:22 AM, Antoine Tremblay wrote:
> Before, on systems that did not support PTRACE_EVENT_CLONE, both GDB and
> GDBServer coordinated with libthread_db.so to insert breakpoints at magic
> locations in libpthread.so, in order to break at thread creation and
> thread death.
>
> Support for thread events was removed from GDBServer as patch:
> https://sourceware.org/ml/gdb-patches/2015-11/msg00466.html
>
> This patch removes support for thread events in GDB.
>
> No regressions found on Ubuntu 14.04 x86_64.
>
> gdb/ChangeLog:
> 	* breakpoint.c (remove_thread_event_breakpoints): Remove.
> 	* breakpoint.h (remove_thread_event_breakpoints): Remove
> 	declaration.
> 	* linux-nat.c (in_pid_list_p): Remove.
> 	(lin_lwp_attach_lwp): Remove.
> 	* linux-nat.h (lin_lwp_attach_lwp): Remove declaration.
> 	* linux-thread-db.c (thread_db_use_events): Remove.
> 	(struct thread_db_info) <td_create_bp_addr>: Remove.
> 	<td_death_bp_addr>: Likewise.
> 	<td_ta_event_addr_p>: Likewise.
> 	<td_ta_set_event_p>: Likewise.
> 	<td_ta_clear_event_p>: Likewise.
> 	<td_ta_event_getmsg_p>: Likewise.
> 	<td_thr_event_enable_p>: Likewise.
> 	(attach_thread): Likewise.
> 	(detach_thread): Likewise.
> 	(have_threads_callback): Likewise.
> 	(have_threads): Likewise.
> 	(enable_thread_event): Likewise.
> 	(enable_thread_event_reporting): Likewise.
> 	(try_thread_db_load_1): Remove td_ta_event_addr, td_ta_set_event,
> 	td_ta_clear_event, td_ta_event_getmsg, td_thr_event_enable
> 	initializations.
> 	(try_thread_db_load_1): Remove enable_thread_event_reporting call.
> 	(disable_thread_event_reporting): Remove.
> 	(record_thread): Adapt to thread_db_use_event removal.
> 	(detach_thread): Remove.
> 	(thread_db_detach): Adapt to thread_db_use_event removal.
> 	(check_event): Remove.
> 	(thread_db_wait): Adapt to thread events support removal.
> 	(thread_db_mourn_inferior): Likewise.
> 	(find_new_threads_callback): Likewise.
> 	(find_new_threads_once): Likewise.
> 	(thread_db_update_thread_list): Likewise.
> ---
>   gdb/breakpoint.c      |  11 --
>   gdb/breakpoint.h      |   2 -
>   gdb/linux-nat.c       | 144 -----------------
>   gdb/linux-nat.h       |   2 -
>   gdb/linux-thread-db.c | 437 ++------------------------------------------------
>   5 files changed, 9 insertions(+), 587 deletions(-)
>
> diff --git a/gdb/breakpoint.c b/gdb/breakpoint.c
> index bc6b2ef..f105042 100644
> --- a/gdb/breakpoint.c
> +++ b/gdb/breakpoint.c
> @@ -7765,17 +7765,6 @@ create_thread_event_breakpoint (struct gdbarch *gdbarch, CORE_ADDR address)
>     return b;
>   }
>
> -void
> -remove_thread_event_breakpoints (void)
> -{
> -  struct breakpoint *b, *b_tmp;
> -
> -  ALL_BREAKPOINTS_SAFE (b, b_tmp)
> -    if (b->type == bp_thread_event
> -	&& b->loc->pspace == current_program_space)
> -      delete_breakpoint (b);
> -}
> -
>   struct lang_and_radix
>     {
>       enum language lang;
> diff --git a/gdb/breakpoint.h b/gdb/breakpoint.h
> index ee8b2e0..7079b75 100644
> --- a/gdb/breakpoint.h
> +++ b/gdb/breakpoint.h
> @@ -1498,8 +1498,6 @@ extern void remove_solib_event_breakpoints (void);
>      delete at next stop disposition.  */
>   extern void remove_solib_event_breakpoints_at_next_stop (void);
>
> -extern void remove_thread_event_breakpoints (void);
> -
>   extern void disable_breakpoints_in_shlibs (void);
>
>   /* This function returns TRUE if ep is a catchpoint.  */
> diff --git a/gdb/linux-nat.c b/gdb/linux-nat.c
> index 9bc1324..95192f6 100644
> --- a/gdb/linux-nat.c
> +++ b/gdb/linux-nat.c
> @@ -345,17 +345,6 @@ add_to_pid_list (struct simple_pid_list **listp, int pid, int status)
>   }
>
>   static int
> -in_pid_list_p (struct simple_pid_list *list, int pid)
> -{
> -  struct simple_pid_list *p;
> -
> -  for (p = list; p != NULL; p = p->next)
> -    if (p->pid == pid)
> -      return 1;
> -  return 0;
> -}
> -
> -static int
>   pull_pid_from_list (struct simple_pid_list **listp, int pid, int *statusp)
>   {
>     struct simple_pid_list **p;
> @@ -1044,139 +1033,6 @@ linux_nat_post_attach_wait (ptid_t ptid, int first, int *cloned,
>     return status;
>   }
>
> -/* Attach to the LWP specified by PID.  Return 0 if successful, -1 if
> -   the new LWP could not be attached, or 1 if we're already auto
> -   attached to this thread, but haven't processed the
> -   PTRACE_EVENT_CLONE event of its parent thread, so we just ignore
> -   its existance, without considering it an error.  */
> -
> -int
> -lin_lwp_attach_lwp (ptid_t ptid)
> -{
> -  struct lwp_info *lp;
> -  int lwpid;
> -
> -  gdb_assert (ptid_lwp_p (ptid));
> -
> -  lp = find_lwp_pid (ptid);
> -  lwpid = ptid_get_lwp (ptid);
> -
> -  /* We assume that we're already attached to any LWP that is already
> -     in our list of LWPs.  If we're not seeing exit events from threads
> -     and we've had PID wraparound since we last tried to stop all threads,
> -     this assumption might be wrong; fortunately, this is very unlikely
> -     to happen.  */
> -  if (lp == NULL)
> -    {
> -      int status, cloned = 0, signalled = 0;
> -
> -      if (ptrace (PTRACE_ATTACH, lwpid, 0, 0) < 0)
> -	{
> -	  if (linux_supports_tracefork ())
> -	    {
> -	      /* If we haven't stopped all threads when we get here,
> -		 we may have seen a thread listed in thread_db's list,
> -		 but not processed the PTRACE_EVENT_CLONE yet.  If
> -		 that's the case, ignore this new thread, and let
> -		 normal event handling discover it later.  */
> -	      if (in_pid_list_p (stopped_pids, lwpid))
> -		{
> -		  /* We've already seen this thread stop, but we
> -		     haven't seen the PTRACE_EVENT_CLONE extended
> -		     event yet.  */
> -		  if (debug_linux_nat)
> -		    fprintf_unfiltered (gdb_stdlog,
> -					"LLAL: attach failed, but already seen "
> -					"this thread %s stop\n",
> -					target_pid_to_str (ptid));
> -		  return 1;
> -		}
> -	      else
> -		{
> -		  int new_pid;
> -		  int status;
> -
> -		  if (debug_linux_nat)
> -		    fprintf_unfiltered (gdb_stdlog,
> -					"LLAL: attach failed, and haven't seen "
> -					"this thread %s stop yet\n",
> -					target_pid_to_str (ptid));
> -
> -		  /* We may or may not be attached to the LWP already.
> -		     Try waitpid on it.  If that errors, we're not
> -		     attached to the LWP yet.  Otherwise, we're
> -		     already attached.  */
> -		  gdb_assert (lwpid > 0);
> -		  new_pid = my_waitpid (lwpid, &status, WNOHANG);
> -		  if (new_pid == -1 && errno == ECHILD)
> -		    new_pid = my_waitpid (lwpid, &status, __WCLONE | WNOHANG);
> -		  if (new_pid != -1)
> -		    {
> -		      if (new_pid == 0)
> -			{
> -			  /* The child hasn't stopped for its initial
> -			     SIGSTOP stop yet.  */
> -			  if (debug_linux_nat)
> -			    fprintf_unfiltered (gdb_stdlog,
> -						"LLAL: child hasn't "
> -						"stopped yet\n");
> -			}
> -		      else if (WIFSTOPPED (status))
> -			{
> -			  if (debug_linux_nat)
> -			    fprintf_unfiltered (gdb_stdlog,
> -						"LLAL: adding to stopped_pids\n");
> -			  add_to_pid_list (&stopped_pids, lwpid, status);
> -			}
> -		      return 1;
> -		    }
> -		}
> -	    }
> -
> -	  /* If we fail to attach to the thread, issue a warning,
> -	     but continue.  One way this can happen is if thread
> -	     creation is interrupted; as of Linux kernel 2.6.19, a
> -	     bug may place threads in the thread list and then fail
> -	     to create them.  */
> -	  warning (_("Can't attach %s: %s"), target_pid_to_str (ptid),
> -		   safe_strerror (errno));
> -	  return -1;
> -	}
> -
> -      if (debug_linux_nat)
> -	fprintf_unfiltered (gdb_stdlog,
> -			    "LLAL: PTRACE_ATTACH %s, 0, 0 (OK)\n",
> -			    target_pid_to_str (ptid));
> -
> -      status = linux_nat_post_attach_wait (ptid, 0, &cloned, &signalled);
> -      if (!WIFSTOPPED (status))
> -	return 1;
> -
> -      lp = add_lwp (ptid);
> -      lp->stopped = 1;
> -      lp->last_resume_kind = resume_stop;
> -      lp->cloned = cloned;
> -      lp->signalled = signalled;
> -      if (WSTOPSIG (status) != SIGSTOP)
> -	{
> -	  lp->resumed = 1;
> -	  lp->status = status;
> -	}
> -
> -      target_post_attach (ptid_get_lwp (lp->ptid));
> -
> -      if (debug_linux_nat)
> -	{
> -	  fprintf_unfiltered (gdb_stdlog,
> -			      "LLAL: waitpid %s received %s\n",
> -			      target_pid_to_str (ptid),
> -			      status_to_str (status));
> -	}
> -    }
> -
> -  return 0;
> -}
> -
>   static void
>   linux_nat_create_inferior (struct target_ops *ops,
>   			   char *exec_file, char *allargs, char **env,
> diff --git a/gdb/linux-nat.h b/gdb/linux-nat.h
> index f7b45f7..f5ec74e 100644
> --- a/gdb/linux-nat.h
> +++ b/gdb/linux-nat.h
> @@ -141,8 +141,6 @@ extern void lin_thread_get_thread_signals (sigset_t *mask);
>   void linux_proc_pending_signals (int pid, sigset_t *pending,
>   				 sigset_t *blocked, sigset_t *ignored);
>
> -extern int lin_lwp_attach_lwp (ptid_t ptid);
> -
>   /* For linux_stop_lwp see nat/linux-nat.h.  */
>
>   /* Stop all LWPs, synchronously.  (Any events that trigger while LWPs
> diff --git a/gdb/linux-thread-db.c b/gdb/linux-thread-db.c
> index 229bb0b..8a80ca3 100644
> --- a/gdb/linux-thread-db.c
> +++ b/gdb/linux-thread-db.c
> @@ -78,16 +78,6 @@ static char *libthread_db_search_path;
>      by the "set auto-load libthread-db" command.  */
>   static int auto_load_thread_db = 1;
>
> -/* Returns true if we need to use thread_db thread create/death event
> -   breakpoints to learn about threads.  */
> -
> -static int
> -thread_db_use_events (void)
> -{
> -  /* Not necessary if the kernel supports clone events.  */
> -  return !linux_supports_traceclone ();
> -}
> -
>   /* "show" command for the auto_load_thread_db configuration variable.  */
>
>   static void
> @@ -161,30 +151,14 @@ struct thread_db_info
>        be able to ignore such stale entries.  */
>     int need_stale_parent_threads_check;
>
> -  /* 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;
> -
> -  /* Location of the thread death event breakpoint.  */
> -  CORE_ADDR td_death_bp_addr;
> -
>     /* Pointers to the libthread_db functions.  */
>
>     td_init_ftype *td_init_p;
>     td_ta_new_ftype *td_ta_new_p;
>     td_ta_map_lwp2thr_ftype *td_ta_map_lwp2thr_p;
>     td_ta_thr_iter_ftype *td_ta_thr_iter_p;
> -  td_ta_event_addr_ftype *td_ta_event_addr_p;
> -  td_ta_set_event_ftype *td_ta_set_event_p;
> -  td_ta_clear_event_ftype *td_ta_clear_event_p;
> -  td_ta_event_getmsg_ftype * td_ta_event_getmsg_p;
>     td_thr_validate_ftype *td_thr_validate_p;
>     td_thr_get_info_ftype *td_thr_get_info_p;
> -  td_thr_event_enable_ftype *td_thr_event_enable_p;
>     td_thr_tls_get_addr_ftype *td_thr_tls_get_addr_p;
>     td_thr_tlsbase_ftype *td_thr_tlsbase_p;
>   };
> @@ -273,12 +247,6 @@ delete_thread_db_info (int pid)
>     xfree (info);
>   }
>
> -/* Prototypes for local functions.  */
> -static int attach_thread (ptid_t ptid, const td_thrhandle_t *th_p,
> -			  const td_thrinfo_t *ti_p);
> -static void detach_thread (ptid_t ptid);
> -
> -
>   /* Use "struct private_thread_info" to cache thread state.  This is
>      a substantial optimization.  */
>
> @@ -359,30 +327,7 @@ thread_db_err_str (td_err_e err)
>         return buf;
>       }
>   }
> -
> -/* Return 1 if any threads have been registered.  There may be none if
> -   the threading library is not fully initialized yet.  */
> -
> -static int
> -have_threads_callback (struct thread_info *thread, void *args)
> -{
> -  int pid = * (int *) args;
> -
> -  if (ptid_get_pid (thread->ptid) != pid)
> -    return 0;
> -
> -  return thread->priv != NULL;
> -}
> -
> -static int
> -have_threads (ptid_t ptid)
> -{
> -  int pid = ptid_get_pid (ptid);
> -
> -  return iterate_over_threads (have_threads_callback, &pid) != NULL;
> -}
>
> -
>   /* Fetch the user-level thread id of PTID.  */
>
>   static struct thread_info *
> @@ -455,37 +400,6 @@ verbose_dlsym (void *handle, const char *name)
>     return sym;
>   }
>
> -static td_err_e
> -enable_thread_event (td_event_e event, CORE_ADDR *bp)
> -{
> -  td_notify_t notify;
> -  td_err_e err;
> -  struct thread_db_info *info;
> -
> -  info = get_thread_db_info (ptid_get_pid (inferior_ptid));
> -
> -  /* Access an lwp we know is stopped.  */
> -  info->proc_handle.ptid = inferior_ptid;
> -
> -  /* Get the breakpoint address for thread EVENT.  */
> -  err = info->td_ta_event_addr_p (info->thread_agent, event, &notify);
> -  if (err != TD_OK)
> -    return err;
> -
> -  /* Set up the breakpoint.  */
> -  gdb_assert (exec_bfd);
> -  (*bp) = (gdbarch_convert_from_func_ptr_addr
> -	   (target_gdbarch (),
> -	    /* Do proper sign extension for the target.  */
> -	    (bfd_get_sign_extend_vma (exec_bfd) > 0
> -	     ? (CORE_ADDR) (intptr_t) notify.u.bptaddr
> -	     : (CORE_ADDR) (uintptr_t) notify.u.bptaddr),
> -	    &current_target));
> -  create_thread_event_breakpoint (target_gdbarch (), *bp);
> -
> -  return TD_OK;
> -}
> -
>   /* Verify inferior's '\0'-terminated symbol VER_SYMBOL starts with "%d.%d" and
>      return 1 if this version is lower (and not equal) to
>      VER_MAJOR_MIN.VER_MINOR_MIN.  Return 0 in all other cases.  */
> @@ -517,68 +431,6 @@ inferior_has_bug (const char *ver_symbol, int ver_major_min, int ver_minor_min)
>     return retval;
>   }
>
> -static void
> -enable_thread_event_reporting (void)
> -{
> -  td_thr_events_t events;
> -  td_err_e err;
> -  struct thread_db_info *info;
> -
> -  info = get_thread_db_info (ptid_get_pid (inferior_ptid));
> -
> -  /* We cannot use the thread event reporting facility if these
> -     functions aren't available.  */
> -  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.  */
> -  td_event_emptyset (&events);
> -  td_event_addset (&events, TD_CREATE);
> -
> -  /* There is a bug fixed between linuxthreads 2.1.3 and 2.2 by
> -       commit 2e4581e4fba917f1779cd0a010a45698586c190a
> -       * manager.c (pthread_exited): Correctly report event as TD_REAP
> -       instead of TD_DEATH.  Fix comments.
> -     where event reporting facility is broken for TD_DEATH events,
> -     so don't enable it if we have glibc but a lower version.  */
> -  if (!inferior_has_bug ("__linuxthreads_version", 2, 2))
> -    td_event_addset (&events, TD_DEATH);
> -
> -  err = info->td_ta_set_event_p (info->thread_agent, &events);
> -  if (err != TD_OK)
> -    {
> -      warning (_("Unable to set global thread event mask: %s"),
> -	       thread_db_err_str (err));
> -      return;
> -    }
> -
> -  /* Delete previous thread event breakpoints, if any.  */
> -  remove_thread_event_breakpoints ();
> -  info->td_create_bp_addr = 0;
> -  info->td_death_bp_addr = 0;
> -
> -  /* Set up the thread creation event.  */
> -  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"),
> -	       thread_db_err_str (err));
> -      return;
> -    }
> -
> -  /* Set up the thread death event.  */
> -  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"),
> -	       thread_db_err_str (err));
> -      return;
> -    }
> -}
> -
>   /* Similar as thread_db_find_new_threads_1, but try to silently ignore errors
>      if appropriate.
>
> @@ -716,11 +568,6 @@ try_thread_db_load_1 (struct thread_db_info *info)
>     CHK (TDB_VERBOSE_DLSYM (info, td_thr_get_info));
>
>     /* These are not essential.  */
> -  TDB_DLSYM (info, td_ta_event_addr);
> -  TDB_DLSYM (info, td_ta_set_event);
> -  TDB_DLSYM (info, td_ta_clear_event);
> -  TDB_DLSYM (info, td_ta_event_getmsg);
> -  TDB_DLSYM (info, td_thr_event_enable);
>     TDB_DLSYM (info, td_thr_tls_get_addr);
>     TDB_DLSYM (info, td_thr_tlsbase);
>
> @@ -784,10 +631,6 @@ try_thread_db_load_1 (struct thread_db_info *info)
>     if (thread_db_list->next == NULL)
>       push_target (&thread_db_ops);
>
> -  /* Enable event reporting, but not when debugging a core file.  */
> -  if (target_has_execution && thread_db_use_events ())
> -    enable_thread_event_reporting ();
> -
>     return 1;
>   }
>
> @@ -1096,23 +939,6 @@ thread_db_load (void)
>   }
>
>   static void
> -disable_thread_event_reporting (struct thread_db_info *info)
> -{
> -  if (info->td_ta_clear_event_p != NULL)
> -    {
> -      td_thr_events_t events;
> -
> -      /* Set the process wide mask saying we aren't interested in any
> -	 events anymore.  */
> -      td_event_fillset (&events);
> -      info->td_ta_clear_event_p (info->thread_agent, &events);
> -    }
> -
> -  info->td_create_bp_addr = 0;
> -  info->td_death_bp_addr = 0;
> -}
> -
> -static void
>   check_thread_signals (void)
>   {
>     if (!thread_signals)
> @@ -1219,75 +1045,6 @@ update_thread_state (struct private_thread_info *priv,
>   		 || ti_p->ti_state == TD_THR_ZOMBIE);
>   }
>
> -/* Attach to a new thread.  This function is called when we receive a
> -   TD_CREATE event or when we iterate over all threads and find one
> -   that wasn't already in our list.  Returns true on success.  */
> -
> -static int
> -attach_thread (ptid_t ptid, const td_thrhandle_t *th_p,
> -	       const td_thrinfo_t *ti_p)
> -{
> -  struct thread_info *tp;
> -  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
> -     may have iterated over all threads between the thread creation
> -     and the TD_CREATE event, for instance when the user has issued
> -     the `info threads' command before the SIGTRAP for hitting the
> -     thread creation breakpoint was reported.  Alternatively, the
> -     thread may have exited and a new one been created with the same
> -     thread ID.  In the first case we don't need to do anything; in
> -     the second case we should discard information about the dead
> -     thread and attach to the new one.  */
> -  tp = find_thread_ptid (ptid);
> -  if (tp != NULL)
> -    {
> -      /* If tp->priv is NULL, then GDB is already attached to this
> -	 thread, but we do not know anything about it.  We can learn
> -	 about it here.  This can only happen if we have some other
> -	 way besides libthread_db to notice new threads (i.e.
> -	 PTRACE_EVENT_CLONE); assume the same mechanism notices thread
> -	 exit, so this can not be a stale thread recreated with the
> -	 same ID.  */
> -      if (tp->priv != NULL)
> -	{
> -	  if (!tp->priv->dying)
> -	    return 0;
> -
> -	  delete_thread (ptid);
> -	  tp = NULL;
> -	}
> -    }
> -
> -  /* Under GNU/Linux, we have to attach to each and every thread.  */
> -  if (target_has_execution
> -      && tp == NULL)
> -    {
> -      int res;
> -
> -      res = lin_lwp_attach_lwp (ptid_build (ptid_get_pid (ptid),
> -					    ti_p->ti_lid, 0));
> -      if (res < 0)
> -	{
> -	  /* Error, stop iterating.  */
> -	  return 0;
> -	}
> -      else if (res > 0)
> -	{
> -	  /* Pretend this thread doesn't exist yet, and keep
> -	     iterating.  */
> -	  return 1;
> -	}
> -
> -      /* Otherwise, we sucessfully attached to the thread.  */
> -    }
> -
> -  info = get_thread_db_info (ptid_get_pid (ptid));
> -  record_thread (info, tp, ptid, th_p, ti_p);
> -  return 1;
> -}
> -
>   /* Record a new thread in GDB's thread list.  Creates the thread's
>      private info.  If TP is NULL or TP is marked as having exited,
>      creates a new thread.  Otherwise, uses TP.  */
> @@ -1323,16 +1080,6 @@ record_thread (struct thread_db_info *info,
>     else
>       tp->priv = priv;
>
> -  /* Enable thread event reporting for this thread, except when
> -     debugging a core file.  */
> -  if (target_has_execution && thread_db_use_events () && new_thread)
> -    {
> -      err = info->td_thr_event_enable_p (th_p, 1);
> -      if (err != TD_OK)
> -	error (_("Cannot enable thread event reporting for %s: %s"),
> -	       target_pid_to_str (ptid), thread_db_err_str (err));
> -    }
> -
>     if (target_has_execution)
>       check_thread_signals ();
>
> @@ -1340,24 +1087,6 @@ record_thread (struct thread_db_info *info,
>   }
>
>   static void
> -detach_thread (ptid_t ptid)
> -{
> -  struct thread_info *thread_info;
> -
> -  /* Don't delete the thread now, because it still reports as active
> -     until it has executed a few instructions after the event
> -     breakpoint - if we deleted it now, "info threads" would cause us
> -     to re-attach to it.  Just mark it as having had a TD_DEATH
> -     event.  This means that we won't delete it from our thread list
> -     until we notice that it's dead (via prune_threads), or until
> -     something re-uses its thread ID.  We'll report the thread exit
> -     when the underlying LWP dies.  */
> -  thread_info = find_thread_ptid (ptid);
> -  gdb_assert (thread_info != NULL && thread_info->priv != NULL);
> -  thread_info->priv->dying = 1;
> -}
> -
> -static void
>   thread_db_detach (struct target_ops *ops, const char *args, int from_tty)
>   {
>     struct target_ops *target_beneath = find_target_beneath (ops);
> @@ -1366,21 +1095,7 @@ thread_db_detach (struct target_ops *ops, const char *args, int from_tty)
>     info = get_thread_db_info (ptid_get_pid (inferior_ptid));
>
>     if (info)
> -    {
> -      if (target_has_execution && thread_db_use_events ())
> -	{
> -	  disable_thread_event_reporting (info);
> -
> -	  /* 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 (ptid_get_pid (inferior_ptid));
> -    }
> +    delete_thread_db_info (ptid_get_pid (inferior_ptid));
>
>     target_beneath->to_detach (target_beneath, args, from_tty);
>
> @@ -1392,101 +1107,6 @@ thread_db_detach (struct target_ops *ops, const char *args, int from_tty)
>       unpush_target (&thread_db_ops);
>   }
>
> -/* Check if PID is currently stopped at the location of a thread event
> -   breakpoint location.  If it is, read the event message and act upon
> -   the event.  */
> -
> -static void
> -check_event (ptid_t ptid)
> -{
> -  struct regcache *regcache = get_thread_regcache (ptid);
> -  struct gdbarch *gdbarch = get_regcache_arch (regcache);
> -  td_event_msg_t msg;
> -  td_thrinfo_t ti;
> -  td_err_e err;
> -  CORE_ADDR stop_pc;
> -  int loop = 0;
> -  struct thread_db_info *info;
> -
> -  info = get_thread_db_info (ptid_get_pid (ptid));
> -
> -  /* Bail out early if we're not at a thread event breakpoint.  */
> -  stop_pc = regcache_read_pc (regcache);
> -  if (!target_supports_stopped_by_sw_breakpoint ())
> -    stop_pc -= gdbarch_decr_pc_after_break (gdbarch);
> -
> -  if (stop_pc != info->td_create_bp_addr
> -      && stop_pc != info->td_death_bp_addr)
> -    return;
> -
> -  /* Access an lwp we know is stopped.  */
> -  info->proc_handle.ptid = ptid;
> -
> -  /* If we have only looked at the first thread before libpthread was
> -     initialized, we may not know its thread ID yet.  Make sure we do
> -     before we add another thread to the list.  */
> -  if (!have_threads (ptid))
> -    thread_db_find_new_threads_1 (ptid);
> -
> -  /* If we are at a create breakpoint, we do not know what new lwp
> -     was created and cannot specifically locate the event message for it.
> -     We have to call td_ta_event_getmsg() to get
> -     the latest message.  Since we have no way of correlating whether
> -     the event message we get back corresponds to our breakpoint, we must
> -     loop and read all event messages, processing them appropriately.
> -     This guarantees we will process the correct message before continuing
> -     from the breakpoint.
> -
> -     Currently, death events are not enabled.  If they are enabled,
> -     the death event can use the td_thr_event_getmsg() interface to
> -     get the message specifically for that lwp and avoid looping
> -     below.  */
> -
> -  loop = 1;
> -
> -  do
> -    {
> -      err = info->td_ta_event_getmsg_p (info->thread_agent, &msg);
> -      if (err != TD_OK)
> -	{
> -	  if (err == TD_NOMSG)
> -	    return;
> -
> -	  error (_("Cannot get thread event message: %s"),
> -		 thread_db_err_str (err));
> -	}
> -
> -      err = info->td_thr_get_info_p (msg.th_p, &ti);
> -      if (err != TD_OK)
> -	error (_("Cannot get thread info: %s"), thread_db_err_str (err));
> -
> -      ptid = ptid_build (ptid_get_pid (ptid), ti.ti_lid, 0);
> -
> -      switch (msg.event)
> -	{
> -	case TD_CREATE:
> -	  /* Call attach_thread whether or not we already know about a
> -	     thread with this thread ID.  */
> -	  attach_thread (ptid, msg.th_p, &ti);
> -
> -	  break;
> -
> -	case TD_DEATH:
> -
> -	  if (!in_thread_list (ptid))
> -	    error (_("Spurious thread death event."));
> -
> -	  detach_thread (ptid);
> -
> -	  break;
> -
> -	default:
> -	  error (_("Spurious thread event."));
> -	}
> -    }
> -  while (loop);
> -}
> -
>   static ptid_t
>   thread_db_wait (struct target_ops *ops,
>   		ptid_t ptid, struct target_waitstatus *ourstatus,
> @@ -1518,17 +1138,9 @@ thread_db_wait (struct target_ops *ops,
>         if (!thread_db_list)
>    	unpush_target (&thread_db_ops);
>
> -      /* Thread event breakpoints are deleted by
> -	 update_breakpoints_after_exec.  */
> -
>         return ptid;
>       }
>
> -  if (ourstatus->kind == TARGET_WAITKIND_STOPPED
> -      && ourstatus->value.sig == GDB_SIGNAL_TRAP)
> -    /* Check for a thread event.  */
> -    check_event (ptid);
> -
>     /* Fill in the thread's user-level thread id and status.  */
>     thread_from_lwp (ptid);
>
> @@ -1544,10 +1156,6 @@ thread_db_mourn_inferior (struct target_ops *ops)
>
>     target_beneath->to_mourn_inferior (target_beneath);
>
> -  /* Delete the old thread event breakpoints.  Do this after mourning
> -     the inferior, so that we don't try to uninsert them.  */
> -  remove_thread_event_breakpoints ();
> -
>     /* Detach thread_db target ops.  */
>     if (!thread_db_list)
>       unpush_target (ops);
> @@ -1595,21 +1203,12 @@ find_new_threads_callback (const td_thrhandle_t *th_p, void *data)
>         /* A thread ID of zero means that this is the main thread, but
>   	 glibc has not yet initialized thread-local storage and the
>   	 pthread library.  We do not know what the thread's TID will
> -	 be yet.  Just enable event reporting and otherwise ignore
> -	 it.  */
> +	 be yet.  */
>
>         /* In that case, we're not stopped in a fork syscall and don't
>   	 need this glibc bug workaround.  */
>         info->need_stale_parent_threads_check = 0;
>
> -      if (target_has_execution && thread_db_use_events ())
> -	{
> -	  err = info->td_thr_event_enable_p (th_p, 1);
> -	  if (err != TD_OK)
> -	    error (_("Cannot enable thread event reporting for LWP %d: %s"),
> -		   (int) ti.ti_lid, thread_db_err_str (err));
> -	}
> -
>         return 0;
>       }
>
> @@ -1627,24 +1226,7 @@ find_new_threads_callback (const td_thrhandle_t *th_p, void *data)
>     ptid = ptid_build (info->pid, ti.ti_lid, 0);
>     tp = find_thread_ptid (ptid);
>     if (tp == NULL || tp->priv == NULL)
> -    {
> -      if (attach_thread (ptid, th_p, &ti))
> -	cb_data->new_threads += 1;
> -      else
> -	/* Problem attaching this thread; perhaps it exited before we
> -	   could attach it?
> -	   This could mean that the thread list inside glibc itself is in
> -	   inconsistent state, and libthread_db could go on looping forever
> -	   (observed with glibc-2.3.6).  To prevent that, terminate
> -	   iteration: thread_db_find_new_threads_2 will retry.  */
> -	return 1;
> -    }
> -  else if (target_has_execution && !thread_db_use_events ())
> -    {
> -      /* Need to update this if not using the libthread_db events
> -	 (particularly, the TD_DEATH event).  */
> -      update_thread_state (tp->priv, &ti);
> -    }
> +    thread_from_lwp (ptid);
>
>     return 0;
>   }
> @@ -1663,7 +1245,7 @@ find_new_threads_once (struct thread_db_info *info, int iteration,
>     data.new_threads = 0;
>
>     /* See comment in thread_db_update_thread_list.  */
> -  gdb_assert (!target_has_execution || thread_db_use_events ());
> +  gdb_assert (!target_has_execution);
>
>     TRY
>       {
> @@ -1789,12 +1371,11 @@ thread_db_update_thread_list (struct target_ops *ops)
>        it.  In the latter case, it's possible that a thread exits just
>        at the exact time that causes GDB to get stuck in an infinite
>        loop.  To avoid pausing all threads whenever the core wants to
> -     refresh the thread list, if the kernel supports clone events
> -     (meaning we're always already attached to all LWPs), we use
> -     thread_from_lwp immediately when we see an LWP stop.  That uses
> -     thread_db entry points that do not walk libpthread's thread list,
> -     so should be safe, as well as more efficient.  */
> -  if (target_has_execution && !thread_db_use_events ())
> +     refresh the thread list, use thread_from_lwp immediately when we
> +     see an LWP stop.  That uses  thread_db entry points that do not
> +     walk libpthread's thread list, so should be safe, as well as
> +     more efficient.  */
> +  if (target_has_execution)
>       ops->beneath->to_update_thread_list (ops->beneath);
>     else
>       thread_db_update_thread_list_td_ta_thr_iter (ops);
>

Pushed in. (Without the dot at the end of the subject)
  

On 12/10/2015 03:49 PM, Antoine Tremblay wrote:

> Pushed in. (Without the dot at the end of the subject)

This broke corethreads.exp though:

Running /home/pedro/gdb/mygit/src/gdb/testsuite/gdb.threads/corethreads.exp ...
FAIL: gdb.threads/corethreads.exp: thread0 found
FAIL: gdb.threads/corethreads.exp: thread1 found

Thanks,
Pedro Alves
  

On 12/10/2015 12:45 PM, Pedro Alves wrote:
> On 12/10/2015 03:49 PM, Antoine Tremblay wrote:
>
>> Pushed in. (Without the dot at the end of the subject)
>
> This broke corethreads.exp though:
>
> Running /home/pedro/gdb/mygit/src/gdb/testsuite/gdb.threads/corethreads.exp ...
> FAIL: gdb.threads/corethreads.exp: thread0 found
> FAIL: gdb.threads/corethreads.exp: thread1 found
>

Right, somehow my buildbot did not see it :(

I'm looking into it now.

Thanks,
Antoine
  

On 12/10/2015 05:57 PM, Antoine Tremblay wrote:
> 
> 
> On 12/10/2015 12:45 PM, Pedro Alves wrote:
>> On 12/10/2015 03:49 PM, Antoine Tremblay wrote:
>>
>>> Pushed in. (Without the dot at the end of the subject)
>>
>> This broke corethreads.exp though:
>>
>> Running /home/pedro/gdb/mygit/src/gdb/testsuite/gdb.threads/corethreads.exp ...
>> FAIL: gdb.threads/corethreads.exp: thread0 found
>> FAIL: gdb.threads/corethreads.exp: thread1 found
>>
> 
> Right, somehow my buildbot did not see it :(
> 
> I'm looking into it now.
> 

It's this hunk:

@@ -1627,24 +1226,7 @@ find_new_threads_callback (const td_thrhandle_t *th_p, void *data)
   ptid = ptid_build (info->pid, ti.ti_lid, 0);
   tp = find_thread_ptid (ptid);
   if (tp == NULL || tp->priv == NULL)
-    {
-      if (attach_thread (ptid, th_p, &ti))
-       cb_data->new_threads += 1;
-      else
-       /* Problem attaching this thread; perhaps it exited before we
-          could attach it?
-          This could mean that the thread list inside glibc itself is in
-          inconsistent state, and libthread_db could go on looping forever
-          (observed with glibc-2.3.6).  To prevent that, terminate
-          iteration: thread_db_find_new_threads_2 will retry.  */
-       return 1;
-    }
-  else if (target_has_execution && !thread_db_use_events ())
-    {
-      /* Need to update this if not using the libthread_db events
-        (particularly, the TD_DEATH event).  */
-      update_thread_state (tp->priv, &ti);
-    }
+    thread_from_lwp (ptid);

   return 0;
 }

We can't use thread_from_lwp with core files.  As mentioned in a comment,
td_ta_map_lwp2thr uses ps_get_thread_area, but we can't use that
currently on core targets, as it uses ptrace directly.

Thanks,
Pedro Alves
  

On 12/10/2015 12:59 PM, Pedro Alves wrote:
> On 12/10/2015 05:57 PM, Antoine Tremblay wrote:
>>
>>
>> On 12/10/2015 12:45 PM, Pedro Alves wrote:
>>> On 12/10/2015 03:49 PM, Antoine Tremblay wrote:
>>>
>>>> Pushed in. (Without the dot at the end of the subject)
>>>
>>> This broke corethreads.exp though:
>>>
>>> Running /home/pedro/gdb/mygit/src/gdb/testsuite/gdb.threads/corethreads.exp ...
>>> FAIL: gdb.threads/corethreads.exp: thread0 found
>>> FAIL: gdb.threads/corethreads.exp: thread1 found
>>>
>>
>> Right, somehow my buildbot did not see it :(
>>
>> I'm looking into it now.
>>
>
> It's this hunk:
>
> @@ -1627,24 +1226,7 @@ find_new_threads_callback (const td_thrhandle_t *th_p, void *data)
>     ptid = ptid_build (info->pid, ti.ti_lid, 0);
>     tp = find_thread_ptid (ptid);
>     if (tp == NULL || tp->priv == NULL)
> -    {
> -      if (attach_thread (ptid, th_p, &ti))
> -       cb_data->new_threads += 1;
> -      else
> -       /* Problem attaching this thread; perhaps it exited before we
> -          could attach it?
> -          This could mean that the thread list inside glibc itself is in
> -          inconsistent state, and libthread_db could go on looping forever
> -          (observed with glibc-2.3.6).  To prevent that, terminate
> -          iteration: thread_db_find_new_threads_2 will retry.  */
> -       return 1;
> -    }
> -  else if (target_has_execution && !thread_db_use_events ())
> -    {
> -      /* Need to update this if not using the libthread_db events
> -        (particularly, the TD_DEATH event).  */
> -      update_thread_state (tp->priv, &ti);
> -    }
> +    thread_from_lwp (ptid);
>
>     return 0;
>   }
>
> We can't use thread_from_lwp with core files.  As mentioned in a comment,
> td_ta_map_lwp2thr uses ps_get_thread_area, but we can't use that
> currently on core targets, as it uses ptrace directly.
>
Right, I think I can replace that directly with :

   if (tp == NULL || tp->priv == NULL)
       record_thread (info, tp, ptid, th_p, &ti);

Sounds ok ? (it fixes the test)

I'll run the full testsuite...
  

On 12/10/2015 06:08 PM, Antoine Tremblay wrote:
> 
> 
> On 12/10/2015 12:59 PM, Pedro Alves wrote:
>> On 12/10/2015 05:57 PM, Antoine Tremblay wrote:
>>>
>>>
>>> On 12/10/2015 12:45 PM, Pedro Alves wrote:
>>>> On 12/10/2015 03:49 PM, Antoine Tremblay wrote:
>>>>
>>>>> Pushed in. (Without the dot at the end of the subject)
>>>>
>>>> This broke corethreads.exp though:
>>>>
>>>> Running /home/pedro/gdb/mygit/src/gdb/testsuite/gdb.threads/corethreads.exp ...
>>>> FAIL: gdb.threads/corethreads.exp: thread0 found
>>>> FAIL: gdb.threads/corethreads.exp: thread1 found
>>>>
>>>
>>> Right, somehow my buildbot did not see it :(
>>>
>>> I'm looking into it now.
>>>
>>
>> It's this hunk:
>>
>> @@ -1627,24 +1226,7 @@ find_new_threads_callback (const td_thrhandle_t *th_p, void *data)
>>     ptid = ptid_build (info->pid, ti.ti_lid, 0);
>>     tp = find_thread_ptid (ptid);
>>     if (tp == NULL || tp->priv == NULL)
>> -    {
>> -      if (attach_thread (ptid, th_p, &ti))
>> -       cb_data->new_threads += 1;
>> -      else
>> -       /* Problem attaching this thread; perhaps it exited before we
>> -          could attach it?
>> -          This could mean that the thread list inside glibc itself is in
>> -          inconsistent state, and libthread_db could go on looping forever
>> -          (observed with glibc-2.3.6).  To prevent that, terminate
>> -          iteration: thread_db_find_new_threads_2 will retry.  */
>> -       return 1;
>> -    }
>> -  else if (target_has_execution && !thread_db_use_events ())
>> -    {
>> -      /* Need to update this if not using the libthread_db events
>> -        (particularly, the TD_DEATH event).  */
>> -      update_thread_state (tp->priv, &ti);
>> -    }
>> +    thread_from_lwp (ptid);
>>
>>     return 0;
>>   }
>>
>> We can't use thread_from_lwp with core files.  As mentioned in a comment,
>> td_ta_map_lwp2thr uses ps_get_thread_area, but we can't use that
>> currently on core targets, as it uses ptrace directly.
>>
> Right, I think I can replace that directly with :
> 
>    if (tp == NULL || tp->priv == NULL)
>        record_thread (info, tp, ptid, th_p, &ti);
> 
> Sounds ok ? (it fixes the test)
> 

I think that's right.

> I'll run the full testsuite...

Thanks,
Pedro Alves