Files
binutils-gdb/gdb/testsuite/gdb.base/sigint-sigwait.exp
Pedro Alves 814fb49ba3 GNU/Linux: Interrupt/Ctrl-C with SIGSTOP instead of SIGINT [PR gdb/9425, PR gdb/14559]
After the "Always put inferiors in their own terminal/session
[gdb/9425, gdb/14559]" change, when a user types "Ctrl-C" while the
inferior is running, GDB is the one who gets the SIGINT, not the
inferior process.  GDB then forwards the SIGINT to the inferior with
target_pass_ctrlc.

That was necessary but not not sufficient to fix PRs gdb/9425,
gdb/14559, because if a program blocks SIGINT with e.g. sigprocmask,
then if GDB sends it a SIGINT, the signal isn't ever delivered to the
process, so ptrace does not intercept it.  You type Ctrl-C, but
nothing happens.  Similarly, if a program uses sigwait to wait for
SIGINT, and the program receives a SIGINT, the SIGINT is _not_
intercepted by ptrace, it goes straight to the inferior.

Now that the Ctrl-C results in a SIGINT sent to GDB instead of the
inferior, we can make GDB interrupt the program any other way we like.
This patch makes non-stop-capable ports interrupt the program with
stop_all_threads / target_stop (i.e., SIGSTOP) instead of
target_pass_ctrlc (i.e., SIGINT), which always works -- SIGSTOP can't
be blocked/ignored.  (In the future GDB may even switch to
PTRACE_INTERRUPT on Linux, though that's a project of its own.)

Another advantage here is with multi-target -- currently, because GDB
relies on Ctrl-C stopping one thread, and then stopping all other
threads in reaction to that stop, target_pass_ctrlc tries to find one
inferior with a thread that is running, in any target.  If the
selected target for some reason fails to process the Ctrl-C request,
then the Ctrl-C ends up lost.  The mechanism implemented in this patch
is different -- we never have to pick a thread, inferior or target --
we're going to stop everything, so we end up in stop_all_threads.

For non-stop, the patch preserves the current behavior of only
stopping one thread in reaction to Ctrl-C, so it can still happen that
the thread that GDB selects to stop disappears and the Ctrl-C ends up
being lost.  However, because now GDB always sees the SIGINT first, we
can change how Ctrl-C behaves there too.  We could even make it
configurable -- for example, it could be reasonable that Ctrl-C simply
drops the CLI back to the prompt, without stopping anything at all.
That might be interesting for "set observer-mode on", at least.

This commit has a user-visible behavior change in all-stop mode --
when you interrupt the program with Ctrl-C, instead of:

  Thread 1 "threads" received signal SIGINT, Interrupt.

You'll get:

  Thread 1 "threads" stopped.

Which is what you already got with the "interrupt" command in non-stop
mode.

If you really want to pass a SIGINT to the program, you can then issue:

  (gdb) signal SIGINT

This commit also adjusts the testsuite to cope with that output
alternative.

With this change, the gdb.base/sigint-sigwait.exp and
gdb.base/sigint-masked-out.exp testcases now pass cleanly on
GNU/Linux, on both native debugging and gdbserver + "maint set
target-non-stop on", so the kfails are adjusted accordingly.

gdb/ChangeLog:
yyyy-mm-dd  Pedro Alves  <pedro@palves.net>

	PR gdb/9425
	PR gdb/14559
	* event-top.c (default_quit_handler): Mark infrun event-loop
	handler with mark_infrun_async_event_handler_ctrl_c instead of
	passing the Ctrl-C to the target directly with target_pass_ctrlc.
	* infcmd.c (interrupt_target_1): On non-stop targets, Mark infrun
	event-loop handler with
	mark_infrun_async_event_handler_interrupt_all instead of using
	target_interrupt.
	* infrun.c (interrupt_all_requested, switch_to_stop_thread)
	(sync_interrupt_all)
	(mark_infrun_async_event_handler_interrupt_all)
	(mark_infrun_async_event_handler_ctrl_c): New.
	(infrun_async_inferior_event_handler): Handle Ctrl-C/interrupt
	requests.
	* infrun.h (mark_infrun_async_event_handler_interrupt_all)
	(mark_infrun_async_event_handler_ctrl_c): Declare.
	* linux-nat.c (wait_for_signal): Don't handle Ctrl-C here.
	(linux_nat_wait_1): Handle it here, by marking the infrun event
	handler, and returning TARGET_WAITKIND_IGNORE with the quit flag
	still set.
	* target.c (maybe_pass_ctrlc): New.
	(target_terminal::inferior, target_terminal::restore_inferior):
	Use it.
	(target_pass_ctrlc): Ass there's no non-stop target pushed.

gdb/testsuite/ChangeLog:
yyyy-mm-dd  Pedro Alves  <pedro@palves.net>

	PR gdb/9425
	PR gdb/14559
	* gdb.base/bp-cmds-continue-ctrl-c.exp: Expect "stopped" in
	alternative to "signal SIGINT".
	* gdb.base/interrupt-daemon-attach.exp: Likewise.
	* gdb.base/interrupt-daemon.exp: Likewise.
	* gdb.base/interrupt-noterm.exp: Likewise.
	* gdb.base/interrupt.exp: Likewise.
	* gdb.base/random-signal.exp: Likewise.
	* gdb.base/range-stepping.exp: Likewise.
	* gdb.gdb/selftest.exp: Likewise.
	* gdb.mi/new-ui-mi-sync.exp: Likewise.
	* gdb.multi/multi-target-interrupt.exp: Likewise.
	* gdb.multi/multi-target-no-resumed.exp: Likewise.
	* gdb.multi/multi-term-settings.exp: Likewise.
	* gdb.server/reconnect-ctrl-c.exp: Likewise.
	* gdb.threads/async.exp: Likewise.
	* gdb.threads/continue-pending-status.exp: Likewise.
	* gdb.threads/leader-exit.exp: Likewise.
	* gdb.threads/manythreads.exp: Likewise.
	* gdb.threads/pthreads.exp: Likewise.
	* gdb.threads/schedlock.exp: Likewise.
	* gdb.threads/sigthread.exp: Likewise.

	* lib/gdb.exp (can_interrupt_blocked_sigint): New.
	* gdb.base/sigint-masked-out.exp (test_ctrl_c)
	(test_interrupt_cmd): Use can_interrupt_blocked_sigint, and don't
	kfail if true.
	* gdb.base/sigint-sigwait.exp (test_ctrl_c, test_interrupt_cmd):
	Likewise.

Change-Id: I83c1b6a20deea1f1909156adde1d60b8f6f2629b
2021-06-14 22:20:45 +01:00

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# Copyright 2021 Free Software Foundation, Inc.
#
# 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/>.
# Make sure that we can interrupt an inferior that has all signals
# masked out, including SIGINT, and then waits for signals with
# sigwait. Test interrupting with both Ctrl-C and the "interrupt"
# command.
standard_testfile
if {[build_executable "failed to build" $testfile $srcfile {debug}]} {
return -1
}
# Test interrupting with Ctrl-C.
proc_with_prefix test_ctrl_c {} {
global binfile
global gdb_prompt
clean_restart $binfile
if ![runto "done"] {
fail "can't run to done function"
return
}
set can_interrupt [can_interrupt_blocked_sigint]
gdb_test_multiple "continue" "" {
-re "Continuing" {
pass $gdb_test_name
}
}
after 200
send_gdb "\003"
global exited_normally_re
gdb_test_multiple "" "ctrl-c stops process" {
-re -wrap "(received signal SIGINT|stopped).*" {
pass $gdb_test_name
}
-re -wrap "Inferior.*exited normally.*" {
if {!$can_interrupt} {
setup_kfail "gdb/9425" *-*-*
}
fail "$gdb_test_name (the program exited)"
}
}
}
# Test interrupting with the "interrupt" command.
proc_with_prefix test_interrupt_cmd {} {
global binfile
global gdb_prompt
clean_restart $binfile
if ![runto "done"] {
fail "can't run to done function"
return
}
set can_interrupt [can_interrupt_blocked_sigint]
gdb_test_multiple "continue&" "" {
-re "Continuing\\.\r\n$gdb_prompt " {
pass $gdb_test_name
}
}
after 200
gdb_test_multiple "interrupt" "" {
-re "$gdb_prompt " {
pass $gdb_test_name
}
}
global exited_normally_re
gdb_test_multiple "" "interrupt cmd stops process" {
-timeout 5
-re "(received signal SIGINT|stopped)" {
pass $gdb_test_name
}
-re "Inferior.*exited normally" {
if {!$can_interrupt} {
setup_kfail "gdb/14559" *-*-*
}
fail "$gdb_test_name (the program exited)"
}
}
}
test_ctrl_c
test_interrupt_cmd