[Bug gdb/13211] Async / Process group and interrupt not working

["cvs-commit at gcc dot gnu.org" <sourceware-bugzilla at sourceware dot org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=13211

--- Comment #1 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Pedro Alves <palves@sourceware.org>:

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=e671cd59d74cec9f53e110ce887128d1eeadb7f2

commit e671cd59d74cec9f53e110ce887128d1eeadb7f2
Author: Pedro Alves <palves@redhat.com>
Date:   Tue Jan 30 14:23:51 2018 +0000

    Per-inferior target_terminal state, fix PR gdb/13211, more

    In my multi-target branch I ran into problems with GDB's terminal
    handling that exist in master as well, with multi-inferior debugging.

    This patch adds a testcase for said problems
    (gdb.multi/multi-term-settings.exp), fixes the problems, fixes PR
    gdb/13211 as well (and adds a testcase for that too,
    gdb.base/interrupt-daemon.exp).

    The basis of the problem I ran into is the following.  Consider a
    scenario where you have:

     - inferior 1 - started with "attach", process is running on some
       other terminal.

     - inferior 2 - started with "run", process is sharing gdb's terminal.

    In this scenario, when you stop/resume both inferiors, you want GDB to
    save/restore the terminal settings of inferior 2, the one that is
    sharing GDB's terminal.  I.e., you want inferior 2 to "own" the
    terminal (in target_terminal::is_ours/target_terminal::is_inferior
    sense).

    Unfortunately, that's not what you get currently.  Because GDB doesn't
    know whether an attached inferior is actually sharing GDB's terminal,
    it tries to save/restore its settings anyway, ignoring errors.  In
    this case, this is pointless, because inferior 1 is running on a
    different terminal, but GDB doesn't know better.

    And then, because it is only possible to have the terminal settings of
    a single inferior be in effect at a time, or make one inferior/pgrp be
    the terminal's foreground pgrp (aka, only one inferior can "own" the
    terminal, ignoring fork children here), if GDB happens to try to
    restore the terminal settings of inferior 1 first, then GDB never
    restores the terminal settings of inferior 2.

    This patch fixes that and a few things more along the way:

     - Moves enum target_terminal::terminal_state out of the
       target_terminal class (it's currently private) and makes it a
       scoped enum so that it can be easily used elsewhere.

     - Replaces the inflow.c:terminal_is_ours boolean with a
       target_terminal_state variable.  This allows distinguishing is_ours
       and is_ours_for_output states.  This allows finally making
       child_terminal_ours_1 do something with its "output_only"
       parameter.

     - Makes each inferior have its own copy of the
       is_ours/is_ours_for_output/is_inferior state.

     - Adds a way for GDB to tell whether the inferior is sharing GDB's
       terminal.  Works best on Linux and Solaris; the fallback works just
       as well as currently.

     - With that, we can remove the inf->attach_flag tests from
       child_terminal_inferior/child_terminal_ours.

     - Currently target_ops.to_ours is responsible for both saving the
       current inferior's terminal state, and restoring gdb's state.
       Because each inferior has its own terminal state (possibly handled
       by different targets in a multi-target world, even), we need to
       split the inferior-saving part from the gdb-restoring part.  The
       patch adds a new target_ops.to_save_inferior target method for
       that.

     - Adds a new target_terminal::save_inferior() function, so that
       sequences like:

         scoped_restore_terminal_state save_state;
         target_terminal::ours_for_output ();

       ... restore back inferiors that were
       target_terminal_state::is_inferior before back to is_inferior, and
       leaves inferiors that were is_ours alone.

     - Along the way, this adds a default implementation of
       target_pass_ctrlc to inflow.c (for inf-child.c), that handles
       passing the Ctrl-C to a process running on GDB's terminal or to
       some other process otherwise.

     - Similarly, adds a new target default implementation of
       target_interrupt, for the "interrupt" command.  The current
       implementation of this hook in inf-ptrace.c kills the whole process
       group, but that's incorrect/undesirable because we may not be
       attached to all processes in the process group.  And also, it's
       incorrect because inferior_process_group() doesn't really return
       the inferior's real process group id if the inferior is not a
       process group leader...  This is the cause of PR gdb/13211 [1],
       which this patch fixes.  While at it, that target method's "ptid"
       parameter is eliminated, because it's not really used.

     - A new test is included that exercises and fixes PR gdb/13211, and
       also fixes a GDB issue reported on stackoverflow that I ran into
       while working on this [2].  The problem is similar to PR gdb/13211,
       except that it also triggers with Ctrl-C.  When debugging a daemon
       (i.e., a process that disconnects from the controlling terminal and
       is not a process group leader, then Ctrl-C doesn't work, you just
       can't interrupt the inferior at all, resulting in a hung debug
       session.  The problem is that since the inferior is no longer
       associated with gdb's session / controlling terminal, then trying
       to put the inferior in the foreground fails.  And so Ctrl-C never
       reaches the inferior directly.  pass_signal is only used when the
       inferior is attached, but that is not the case here.  This is fixed
       by the new child_pass_ctrlc.  Without the fix, the new
       interrupt-daemon.exp testcase fails with timeout waiting for a
       SIGINT that never arrives.

    [1] PR gdb/13211 - Async / Process group and interrupt not working
    https://sourceware.org/bugzilla/show_bug.cgi?id=13211

    [2] GDB not reacting Ctrl-C when after fork() and setsid()
   
https://stackoverflow.com/questions/46101292/gdb-not-reacting-ctrl-c-when-after-fork-and-setsid

    Note this patch does _not_ fix:

     - PR gdb/14559 - The 'interrupt' command does not work if sigwait is in
use
       https://sourceware.org/bugzilla/show_bug.cgi?id=14559

     - PR gdb/9425 - When using "sigwait" GDB doesn't trap SIGINT. Ctrl+C
terminates program when should break gdb.
       https://sourceware.org/bugzilla/show_bug.cgi?id=9425

    The only way to fix that that I know of (without changing the kernel)
    is to make GDB put inferiors in a separate session (create a
    pseudo-tty master/slave pair, make the inferior run with the slave as
    its terminal, and have gdb pump output/input on the master end).

    gdb/ChangeLog:
    2018-01-30  Pedro Alves  <palves@redhat.com>

        PR gdb/13211
        * config.in, configure: Regenerate.
        * configure.ac: Check for getpgid.
        * go32-nat.c (go32_pass_ctrlc): New.
        (go32_target): Install it.
        * inf-child.c (inf_child_target): Install
        child_terminal_save_inferior, child_pass_ctrlc and
        child_interrupt.
        * inf-ptrace.c (inf_ptrace_interrupt): Delete.
        (inf_ptrace_target): No longer install it.
        * infcmd.c (interrupt_target_1): Adjust.
        * inferior.h (child_terminal_save_inferior, child_pass_ctrlc)
        (child_interrupt): Declare.
        (inferior::terminal_state): New.
        * inflow.c (struct terminal_info): Update comments.
        (inferior_process_group): Delete.
        (terminal_is_ours): Delete.
        (gdb_tty_state): New.
        (child_terminal_init): Adjust.
        (is_gdb_terminal, sharing_input_terminal_1)
        (sharing_input_terminal): New functions.
        (child_terminal_inferior): Adjust.  Use sharing_input_terminal.
        Set the process's actual process group in the foreground if
        possible.  Handle is_ours_for_output/is_ours distinction.  Don't
        mark terminal as the inferior's if not sharing GDB's terminal.
        Don't check attach_flag.
        (child_terminal_ours_for_output, child_terminal_ours): Adjust to
        pass down a target_terminal_state.
        (child_terminal_save_inferior): New, factored out from ...
        (child_terminal_ours_1): ... this.  Handle
        target_terminal_state::is_ours_for_output.
        (child_interrupt, child_pass_ctrlc): New.
        (inflow_inferior_exit): Clear the inferior's terminal_state.
        (copy_terminal_info): Copy the inferior's terminal state.
        (_initialize_inflow): Remove reference to terminal_is_ours.
        * inflow.h (inferior_process_group): Delete.
        * nto-procfs.c (nto_handle_sigint, procfs_interrupt): Adjust.
        * procfs.c (procfs_target): Don't install procfs_interrupt.
        (procfs_interrupt): Delete.
        * remote.c (remote_serial_quit_handler): Adjust.
        (remote_interrupt): Remove ptid parameter.  Adjust.
        * target-delegates.c: Regenerate.
        * target.c: Include "terminal.h".
        (target_terminal::terminal_state): Rename to ...
        (target_terminal::m_terminal_state): ... this.
        (target_terminal::init): Adjust.
        (target_terminal::inferior): Adjust to per-inferior
        terminal_state.
        (target_terminal::restore_inferior, target_terminal_is_ours_kind): New.
        (target_terminal::ours, target_terminal::ours_for_output): Use
        target_terminal_is_ours_kind.
        (target_interrupt): Remove ptid parameter.  Adjust.
        (default_target_pass_ctrlc): Adjust.
        * target.h (target_ops::to_terminal_save_inferior): New field.
        (target_ops::to_interrupt): Remove ptid_t parameter.
        (target_interrupt): Remove ptid_t parameter.  Update comment.
        (target_pass_ctrlc): Update comment.
        * target/target.h (target_terminal_state): New scoped enum,
        factored out of ...
        (target_terminal::terminal_state): ... here.
        (target_terminal::inferior): Update comments.
        (target_terminal::restore_inferior): New.
        (target_terminal::is_inferior, target_terminal::is_ours)
        (target_terminal::is_ours_for_output): Adjust.
        (target_terminal::scoped_restore_terminal_state): Adjust to
        rename, and call restore_inferior() instead of inferior().
        (target_terminal::scoped_restore_terminal_state::m_state): Change
        type.
        (target_terminal::terminal_state): Rename to ...
        (target_terminal::m_terminal_state): ... this and change type.

    gdb/gdbserver/ChangeLog:
    2018-01-30  Pedro Alves  <palves@redhat.com>

        PR gdb/13211
        * target.c (target_terminal::terminal_state): Rename to ...
        (target_terminal::m_terminal_state): ... this.

    gdb/testsuite/ChangeLog:
    2018-01-30  Pedro Alves  <palves@redhat.com>

        PR gdb/13211
        * gdb.base/interrupt-daemon.c: New.
        * gdb.base/interrupt-daemon.exp: New.
        * gdb.multi/multi-term-settings.c: New.
        * gdb.multi/multi-term-settings.exp: New.

-- 
You are receiving this mail because:
You are on the CC list for the bug.