[Emacs-diffs] /srv/bzr/emacs/trunk r110152: Simplify and avoid signal-handling races.

[Paul Eggert]

------------------------------------------------------------
revno: 110152
fixes bug: http://debbugs.gnu.org/12471
committer: Paul Eggert <address@hidden>
branch nick: trunk
timestamp: Sun 2012-09-23 01:44:20 -0700
message:
  Simplify and avoid signal-handling races.
  
  * nt/inc/ms-w32.h (emacs_raise): New macro.
  * src/alloc.c (die):
  * src/sysdep.c (emacs_abort) [HAVE_NTGUI]:
  Avoid recursive loop if there's a fatal error in the function itself.
  * src/atimer.c (pending_atimers):
  * src/blockinput.h: Don't include "atimer.h"; no longer needed.
  (interrupt_input_pending): Remove.  All uses removed.
  pending_signals now counts both atimers and ordinary interrupts.
  This is less racy than having three separate pending-signal flags.
  (block_input, unblock_input, totally_unblock_input, unblock_input_to)
  (input_blocked_p):
  Rename from their upper-case counterparts BLOCK_INPUT,
  UNBLOCK_INPUT, TOTALLY_UNBLOCK_INPUT, UNBLOCK_INPUT_TO,
  INPUT_BLOCKED_P, and turn into functions.  All uses changed.
  This makes it easier to access volatile variables more accurately.
  (BLOCK_INPUT_RESIGNAL): Remove.  All uses replaced by unblock_input ().
  (input_blocked_p): Prefer this to 'interrupt_input_blocked', as
  that's more reliable if the code is buggy and sets
  interrupt_input_blocked to a negative value.  All uses changed.
  * src/atimer.c (deliver_alarm_signal):
  Remove.  No need to deliver this to the parent; any thread can
  handle this signal now.  All uses replaced by underlying handler.
  * src/atimer.c (turn_on_atimers):
  * src/dispnew.c (handle_window_change_signal):
  * src/emacs.c (handle_danger_signal):
  * src/keyboard.c (kbd_buffer_get_event):
  Don't reestablish signal handler; not needed with sigaction.
  * src/blockinput.h (UNBLOCK_INPUT_TO, TOTALLY_UNBLOCK_INPUT)
  (UNBLOCK_INPUT_TO):
  Rework to avoid unnecessary accesses to volatile variables.
  (UNBLOCK_INPUT_TO): Now a function.
  (totally_unblock_input, unblock_input): New decls.
  * src/data.c (handle_arith_signal, deliver_arith_signal): Move to sysdep.c
  (init_data): Remove.  Necessary stuff now done in init_signal.
  * src/emacs.c, src/xdisp.c: Include "atimer.h", since we invoke atimer 
functions.
  * src/emacs.c (handle_fatal_signal, deliver_fatal_signal): Move to sysdep.c.
  (fatal_error_code): Remove; no longer needed.
  (terminate_due_to_signal): Rename from fatal_error_backtrace, since
  it doesn't always backtrace.  All uses changed.  No need to reset
  signal to default, since sigaction and/or die does that for us now.
  Use emacs_raise (FOO), not kill (getpid (), FOO).
  (main): Check more-accurately whether we're dumping.
  Move fatal-error setup to sysdep.c
  * src/floatfns.c: Do not include "syssignal.h"; no longer needed.
  * src/gtkutil.c (xg_get_file_name, xg_get_font):
  Remove no-longer-needed signal-mask manipulation.
  * src/keyboard.c, src/process.c (POLL_FOR_INPUT):
  Don't depend on USE_ASYNC_EVENTS, a symbol that is never defined.
  * src/keyboard.c (read_avail_input): Remove.
  All uses replaced by gobble_input.
  (Ftop_level): Use TOTALLY_UNBLOCK_INPUT rather than open code.
  (kbd_buffer_store_event_hold, gobble_input):
  (record_asynch_buffer_change) [USABLE_SIGIO]:
  (store_user_signal_events):
  No need to mess with signal mask.
  (gobble_input): If blocking input and there are terminals, simply
  set pending_signals to 1 and return.  All hooks changed to not
  worry about whether input is blocked.
  (process_pending_signals): Clear pending_signals before processing
  them, in case a signal comes in while we're processing.
  By convention callers now test pending_signals before calling us.
  (UNBLOCK_INPUT_TO, unblock_input, totally_unblock_input):
  New functions, to support changes to blockinput.h.
  (handle_input_available_signal): Now extern.
  (reinvoke_input_signal): Remove.  All uses replaced by
  handle_async_input.
  (quit_count): Now volatile, since a signal handler uses it.
  (handle_interrupt): Now takes bool IN_SIGNAL_HANDLER as arg.  All
  callers changed.  Block SIGINT only if not already blocked.
  Clear sigmask reliably, even if Fsignal returns, which it can.
  Omit unnecessary accesses to volatile var.
  (quit_throw_to_read_char): No need to restore sigmask.
  * src/keyboard.c (gobble_input, handle_user_signal):
  * src/process.c (wait_reading_process_output):
  Call signal-handling code rather than killing ourselves.
  * src/lisp.h: Include <float.h>, for...
  (IEEE_FLOATING_POINT): New macro, moved here to avoid duplication.
  (pending_signals): Now volatile.
  (syms_of_data): Now const if IEEE floating point.
  (handle_input_available_signal) [USABLE_SIGIO]:
  (terminate_due_to_signal, record_child_status_change): New decls.
  * src/process.c (create_process): Avoid disaster if memory is exhausted
  while we're processing a vfork, by tightening the critical section
  around the vfork.
  (send_process_frame, process_sent_to, handle_pipe_signal)
  (deliver_pipe_signal): Remove.  No longer needed, as Emacs now
  ignores SIGPIPE.
  (send_process): No need for setjmp/longjmp any more, since the
  SIGPIPE stuff is now gone.  Instead, report an error if errno
  is EPIPE.
  (record_child_status_change): Now extern.  PID and W are now args.
  Return void, not bool.  All callers changed.
  * src/sysdep.c (wait_debugging) [(BSD_SYSTEM || HPUX) && !defined (__GNU__)]:
  Remove.  All uses removed.  This bug should be fixed now in a
  different way.
  (wait_for_termination_1): Use waitpid rather than sigsuspend,
  and record the child status change directly.  This avoids the
  need to futz with the signal mask.
  (process_fatal_action): Move here from emacs.c.
  (emacs_sigaction_flags): New function, containing
  much of what used to be in emacs_sigaction_init.
  (emacs_sigaction_init): Use it.  Block nonfatal system signals that are
  caught by emacs, to make races less likely.
  (deliver_process_signal): Rename from handle_on_main_thread.
  All uses changed.
  (BACKTRACE_LIMIT_MAX): Now at top level.
  (thread_backtrace_buffer, threadback_backtrace_pointers):
  New static vars.
  (deliver_thread_signal, deliver_fatal_thread_signal):
  New functions, for more-accurate delivery of thread-specific signals.
  (handle_fatal_signal, deliver_fatal_signal): Move here from emacs.c.
  (deliver_arith_signal): Handle in this thread, not
  in the main thread, since it's triggered by this thread.
  (maybe_fatal_sig): New function.
  (init_signals): New arg DUMPING so that we can be more accurate
  about whether we're dumping.  Caller changed.
  Treat thread-specific signals differently from process-general signals.
  Block all signals while handling fatal error; that's safer.
  xsignal from SIGFPE only on non-IEEE hosts, treating it as fatal
  on IEEE hosts.
  When batch, ignore SIGHUP, SIGINT, SIGTERM if they were already ignored.
  Ignore SIGPIPE unless batch.
  (emacs_backtrace): Output backtrace for the appropriate thread,
  which is not necessarily the main thread.
  * src/syssignal.h: Include <stdbool.h>.
  (emacs_raise): New macro.
  * src/xterm.c (x_connection_signal): Remove; no longer needed
  now that we use sigaction.
  (x_connection_closed): No need to mess with sigmask now.
  (x_initialize): No need to reset SIGPIPE handler here, since
  init_signals does this for us now.
modified:
  nt/ChangeLog
  nt/inc/ms-w32.h
  src/ChangeLog
  src/alloc.c
  src/atimer.c
  src/blockinput.h
  src/buffer.c
  src/callproc.c
  src/data.c
  src/dired.c
  src/dispnew.c
  src/dosfns.c
  src/editfns.c
  src/emacs.c
  src/eval.c
  src/fileio.c
  src/floatfns.c
  src/fns.c
  src/fontset.c
  src/frame.c
  src/fringe.c
  src/ftxfont.c
  src/gtkutil.c
  src/image.c
  src/keyboard.c
  src/keyboard.h
  src/keymap.c
  src/lisp.h
  src/lread.c
  src/menu.c
  src/msdos.c
  src/nsfns.m
  src/nsfont.m
  src/nsmenu.m
  src/nsterm.m
  src/print.c
  src/process.c
  src/ralloc.c
  src/search.c
  src/sysdep.c
  src/syssignal.h
  src/term.c
  src/termhooks.h
  src/w16select.c
  src/w32fns.c
  src/w32inevt.c
  src/w32menu.c
  src/w32reg.c
  src/w32select.c
  src/w32term.c
  src/widget.c
  src/window.c
  src/xdisp.c
  src/xfaces.c
  src/xfns.c
  src/xfont.c
  src/xftfont.c
  src/xmenu.c
  src/xselect.c
  src/xsettings.c
  src/xterm.c

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