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binutils-gdb/gdb/infrun.h
Pedro Alves 221e1a37cd remote non-stop: Process initially stopped threads before other commands 
The main motivation for this is making non-stop / all-stop behave
similarly on initial connection, in order to move in the direction of
reimplementing all-stop mode with the remote target always running in
non-stop mode.

When we connect to a remote target in non-stop mode, we may find
threads either running or already stopped.  The act of connecting
itself does not force threads to stop.  To handle that, the remote
non-stop connection is currently roughly like this:

 #1 - Fetch list of remote threads (qXfer:threads:read, qfThreadInfo,
    etc).  All threads are assumed to be running until the target
    reports an asynchronous stop reply for them.

 #2 - Fetch the initial set of threads that were already stopped, with
    the '?'  packet.  (In non-stop, this is coupled with the vStopped
    mechanism to be able to retrieve the status of more than one
    thread.)

The stop replies fetched in #2 are placed in the pending stop reply
queue, and left for the regular event loop to process.  That is,
"target remote" finishes and returns _before_ those stops are
processed.

That means that it's possible to have GDB process further commands
before the initial set of stopped threads is reported to the user.

E.g., before the patch, note how the prompt is printed before the
frame:

 Remote debugging using :9999
 (gdb)
 [Thread 15296] #1 stopped.
 0x0000003615a011f0 in ?? ()

Even though thread #1 was not running, for a moment, the user can see
it as such:

 $ gdb a.out -ex "set non-stop 1" -ex "tar rem :9999"  -ex "info threads" -ex "info registers"
 Remote debugging using :9999
   Id   Target Id         Frame
 * 1    Thread 4772       (running)
 Target is executing.                 <<<<<<< info registers
 (gdb)
 [Thread 4772] #1 stopped.
 0x0000003615a011f0 in ?? ()

To fix that, this commit makes gdb process all threads found already
stopped at connection time, before giving the prompt to the user.

The fix takes a cue from fork-child.c:startup_inferior [1], and
processes the events locally in remote.c, avoiding the whole
wait_for_inferior/handle_inferior_event path.  I decided to try this
approach after noticing that:

 - several cases in handle_inferior_event miss checking stop_soon.
 - we don't want to fetch the thread list in normal_stop.

and trying to fix them was resulting in sprinkling stop_soon checks in
many places, and uglifying normal_stop even more.

While with this patch, I'm avoiding changing GDB's output other than
when the prompt is printed, I think this approach is more flexible if
we do want to change it.  And also, it's likely easier to get rid of
the MI *running event that is still sent for threads that are
initially found stopped, if we want to.

This happens to fix the testsuite too.  All non-stop tests are racy
against "target remote" / gdbserver testing currently.  That is,
sometimes the tests run, but other times they're just skipped without
any indication of PASS/FAIL.  When that happens, the logs show:

 target remote localhost:2346
 Remote debugging using localhost:2346
 (gdb)
 [Thread 25418] #1 stopped.
 0x0000003615a011f0 in ?? ()
 ^CQuit
 (gdb) Remote debugging from host 127.0.0.1
 Killing process(es): 25418
 monitor exit
 (gdb) Remote connection closed
 (gdb) testcase /home/pedro/gdb/mygit/build/../src/gdb/testsuite/gdb.threads/multi-create-ns-info-thr.exp completed in 61 seconds

The trouble here is that there's output after the prompt, and the
regex in question doesn't expect that:

   -re "Remote debugging using .*$serialport_re.*$gdb_prompt $" {
	verbose "Set target to $targetname"
	return 0
    }

[1] - before startup_inferior was added, we'd go through
wait_for_inferior/handle_inferior_event while going through the shell,
and that turned out problematic.

Tested on x86_64 Fedora 20, gdbserver.

gdb/ChangeLog:
2015-08-20  Pedro Alves  <palves@redhat.com>

	* infrun.c (print_target_wait_results): Make extern.
	* infrun.h (print_target_wait_results): Declare.
	* remote.c (set_stop_requested_callback): Delete.
	(process_initial_stop_replies): New function.
	(remote_start_remote): Use it.
	(stop_reply_queue_length): New function.

gdb/testsuite/ChangeLog:
2015-08-20  Pedro Alves  <palves@redhat.com>

	* gdb.server/connect-stopped-target.c: New file.
	* gdb.server/connect-stopped-target.exp: New file.
2015-08-20 18:27:55 +01:00

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/* Copyright (C) 1986-2015 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/>. */
#ifndef INFRUN_H
#define INFRUN_H 1
#include "symtab.h"
struct target_waitstatus;
struct frame_info;
struct address_space;
/* True if we are debugging run control. */
extern unsigned int debug_infrun;
/* True if we are debugging displaced stepping. */
extern int debug_displaced;
/* Nonzero if we want to give control to the user when we're notified
of shared library events by the dynamic linker. */
extern int stop_on_solib_events;
/* Are we simulating synchronous execution? This is used in async gdb
to implement the 'run', 'continue' etc commands, which will not
redisplay the prompt until the execution is actually over. */
extern int sync_execution;
/* True if execution commands resume all threads of all processes by
default; otherwise, resume only threads of the current inferior
process. */
extern int sched_multi;
/* When set, stop the 'step' command if we enter a function which has
no line number information. The normal behavior is that we step
over such function. */
extern int step_stop_if_no_debug;
/* If set, the inferior should be controlled in non-stop mode. In
this mode, each thread is controlled independently. Execution
commands apply only to the selected thread by default, and stop
events stop only the thread that had the event -- the other threads
are kept running freely. */
extern int non_stop;
/* When set (default), the target should attempt to disable the
operating system's address space randomization feature when
starting an inferior. */
extern int disable_randomization;
/* Reverse execution. */
enum exec_direction_kind
{
EXEC_FORWARD,
EXEC_REVERSE
};
/* The current execution direction. This should only be set to enum
exec_direction_kind values. It is only an int to make it
compatible with make_cleanup_restore_integer. */
extern int execution_direction;
extern void start_remote (int from_tty);
/* Clear out all variables saying what to do when inferior is
continued or stepped. First do this, then set the ones you want,
then call `proceed'. STEP indicates whether we're preparing for a
step/stepi command. */
extern void clear_proceed_status (int step);
extern void proceed (CORE_ADDR, enum gdb_signal);
/* The `resume' routine should only be called in special circumstances.
Normally, use `proceed', which handles a lot of bookkeeping. */
extern void resume (enum gdb_signal);
/* Return a ptid representing the set of threads that we will proceed,
in the perspective of the user/frontend. We may actually resume
fewer threads at first, e.g., if a thread is stopped at a
breakpoint that needs stepping-off, but that should not be visible
to the user/frontend, and neither should the frontend/user be
allowed to proceed any of the threads that happen to be stopped for
internal run control handling, if a previous command wanted them
resumed. */
extern ptid_t user_visible_resume_ptid (int step);
extern void wait_for_inferior (void);
extern void normal_stop (void);
extern void get_last_target_status (ptid_t *ptid,
struct target_waitstatus *status);
extern void prepare_for_detach (void);
extern void fetch_inferior_event (void *);
extern void init_wait_for_inferior (void);
extern void insert_step_resume_breakpoint_at_sal (struct gdbarch *,
struct symtab_and_line ,
struct frame_id);
/* Returns true if we're trying to step past the instruction at
ADDRESS in ASPACE. */
extern int stepping_past_instruction_at (struct address_space *aspace,
CORE_ADDR address);
/* Returns true if we're trying to step past an instruction that
triggers a non-steppable watchpoint. */
extern int stepping_past_nonsteppable_watchpoint (void);
extern void set_step_info (struct frame_info *frame,
struct symtab_and_line sal);
/* Several print_*_reason helper functions to print why the inferior
has stopped to the passed in UIOUT. */
/* Signal received, print why the inferior has stopped. */
extern void print_signal_received_reason (struct ui_out *uiout,
enum gdb_signal siggnal);
/* Print why the inferior has stopped. We are done with a
step/next/si/ni command, print why the inferior has stopped. */
extern void print_end_stepping_range_reason (struct ui_out *uiout);
/* The inferior was terminated by a signal, print why it stopped. */
extern void print_signal_exited_reason (struct ui_out *uiout,
enum gdb_signal siggnal);
/* The inferior program is finished, print why it stopped. */
extern void print_exited_reason (struct ui_out *uiout, int exitstatus);
/* Reverse execution: target ran out of history info, print why the
inferior has stopped. */
extern void print_no_history_reason (struct ui_out *uiout);
extern void print_stop_event (struct target_waitstatus *ws);
/* Pretty print the results of target_wait, for debugging purposes. */
extern void print_target_wait_results (ptid_t waiton_ptid, ptid_t result_ptid,
const struct target_waitstatus *ws);
extern int signal_stop_state (int);
extern int signal_print_state (int);
extern int signal_pass_state (int);
extern int signal_stop_update (int, int);
extern int signal_print_update (int, int);
extern int signal_pass_update (int, int);
extern void update_signals_program_target (void);
/* Clear the convenience variables associated with the exit of the
inferior. Currently, those variables are $_exitcode and
$_exitsignal. */
extern void clear_exit_convenience_vars (void);
/* Dump LEN bytes at BUF in hex to FILE, followed by a newline. */
extern void displaced_step_dump_bytes (struct ui_file *file,
const gdb_byte *buf, size_t len);
extern struct displaced_step_closure *get_displaced_step_closure_by_addr
(CORE_ADDR addr);
extern void update_observer_mode (void);
extern void signal_catch_update (const unsigned int *);
/* In some circumstances we allow a command to specify a numeric
signal. The idea is to keep these circumstances limited so that
users (and scripts) develop portable habits. For comparison,
POSIX.2 `kill' requires that 1,2,3,6,9,14, and 15 work (and using a
numeric signal at all is obsolescent. We are slightly more lenient
and allow 1-15 which should match host signal numbers on most
systems. Use of symbolic signal names is strongly encouraged. */
enum gdb_signal gdb_signal_from_command (int num);
/* Enables/disables infrun's async event source in the event loop. */
extern void infrun_async (int enable);
/* The global queue of threads that need to do a step-over operation
to get past e.g., a breakpoint. */
extern struct thread_info *step_over_queue_head;
#endif /* INFRUN_H */
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