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.

Fixes: debbugs:12471

1 files changed, 12 insertions, 12 deletions

diff --git a/src/buffer.c b/src/buffer.c
index 22624e33a4b..356a308fce6 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -550,11 +550,11 @@ even if it is dead.  The return value is never nil.  */)
   b->indirections = 0;
 
   BUF_GAP_SIZE (b) = 20;
-  BLOCK_INPUT;
+  block_input ();
   /* We allocate extra 1-byte at the tail and keep it always '\0' for
      anchoring a search.  */
   alloc_buffer_text (b, BUF_GAP_SIZE (b) + 1);
-  UNBLOCK_INPUT;
+  unblock_input ();
   if (! BUF_BEG_ADDR (b))
     buffer_memory_full (BUF_GAP_SIZE (b) + 1);
 
@@ -1923,7 +1923,7 @@ cleaning up all windows currently displaying the buffer to be killed. */)
 
   bset_name (b, Qnil);
 
-  BLOCK_INPUT;
+  block_input ();
   if (b->base_buffer)
     {
       /* Notify our base buffer that we don't share the text anymore.  */
@@ -1946,7 +1946,7 @@ cleaning up all windows currently displaying the buffer to be killed. */)
       b->width_run_cache = 0;
     }
   bset_width_table (b, Qnil);
-  UNBLOCK_INPUT;
+  unblock_input ();
   bset_undo_list (b, Qnil);
 
   /* Run buffer-list-update-hook.  */
@@ -5032,7 +5032,7 @@ alloc_buffer_text (struct buffer *b, ptrdiff_t nbytes)
 {
   void *p;
 
-  BLOCK_INPUT;
+  block_input ();
 #if defined USE_MMAP_FOR_BUFFERS
   p = mmap_alloc ((void **) &b->text->beg, nbytes);
 #elif defined REL_ALLOC
@@ -5043,12 +5043,12 @@ alloc_buffer_text (struct buffer *b, ptrdiff_t nbytes)
 
   if (p == NULL)
     {
-      UNBLOCK_INPUT;
+      unblock_input ();
       memory_full (nbytes);
     }
 
   b->text->beg = (unsigned char *) p;
-  UNBLOCK_INPUT;
+  unblock_input ();
 }
 
 /* Enlarge buffer B's text buffer by DELTA bytes.  DELTA < 0 means
@@ -5060,7 +5060,7 @@ enlarge_buffer_text (struct buffer *b, ptrdiff_t delta)
   void *p;
   ptrdiff_t nbytes = (BUF_Z_BYTE (b) - BUF_BEG_BYTE (b) + BUF_GAP_SIZE (b) + 1
                       + delta);
-  BLOCK_INPUT;
+  block_input ();
 #if defined USE_MMAP_FOR_BUFFERS
   p = mmap_realloc ((void **) &b->text->beg, nbytes);
 #elif defined REL_ALLOC
@@ -5071,12 +5071,12 @@ enlarge_buffer_text (struct buffer *b, ptrdiff_t delta)
 
   if (p == NULL)
     {
-      UNBLOCK_INPUT;
+      unblock_input ();
       memory_full (nbytes);
     }
 
   BUF_BEG_ADDR (b) = (unsigned char *) p;
-  UNBLOCK_INPUT;
+  unblock_input ();
 }
 
 
@@ -5085,7 +5085,7 @@ enlarge_buffer_text (struct buffer *b, ptrdiff_t delta)
 static void
 free_buffer_text (struct buffer *b)
 {
-  BLOCK_INPUT;
+  block_input ();
 
 #if defined USE_MMAP_FOR_BUFFERS
   mmap_free ((void **) &b->text->beg);
@@ -5096,7 +5096,7 @@ free_buffer_text (struct buffer *b)
 #endif
 
   BUF_BEG_ADDR (b) = NULL;
-  UNBLOCK_INPUT;
+  unblock_input ();
 }