Re: [PATCH][PR gdb/8527] Interrupt not functional in Eclipse/CDT on Solaris

["Rainer Orth" <ro at CeBiTec dot Uni-Bielefeld dot DE>]

Hi Joel,

>>> In Solaris:
>>> 
>>> If gdb attaches to a process that either has no controlling terminal,
>>> or the controlling terminal differs from the one gdb is running under,
>>> break/^C doesn't interrupt the debugged process.
>>> 
>>> This is a fix that was proposed for this problem quite awhile ago but
>>> never implemented; it's been in the Adacore GDB branch for quite
>>> awhile.
>>> 
>>> Without going into unnecessary details I cannot easily run the test
>>> suite against this change right now.  If this patch gets rejected
>>> based on that, when I have time I'll see about getting IllumOS
>>> installed in a VM and test it there, but the problem was originally
>>> found in sparc Solaris.
>>> 
>>> ----
>>> 
>>> note: this patch was tested against 8.1.1.  It looks like it probably
>>> still applies on the 8.2 branch, but I won't be able to test it until
>>> 8.2 is released.
>>> 
>>> -brian
>>> 
>>> ps, my assignment/release forms were completed/received 10/30/2017
>>
>>> gdb/Changelog:
>>> 2018-08-07  Brian Vandenberg  <phantall@gmail.com>
>>> 
>>> 	PR gdb/8527
>>> 	* procfs.c (proc_wait_for_stop): calls to set_sigint_trap and
>>> 	clear_sigint_trap.
>>
>> I'm not sure anyone took the time to answer this message; if not,
>> I apologize.
>
> I'm sorry it took me so long, too, first to get well again and then to
> get to this.
>
>> I can testify that, for as long as we got the patch in the AdaCore
>> sources, we never noticed any ill effect. We never got to validate
>> it against the official testsuite, unfortunately, because for some
>> reason, when I did so, our Solaris machines would badly crash. Did
>
> This is weird: the only time I saw something like this was with a few
> Solaris 12/11.4 Beta builds.
>
>> you run the testsuite before and after the patch, by any chance?
>>
>> Rainer (in Cc:) is our maintainer for Solaris, so he may have an opinion.
>
> I've now regtested the patch on both amd64-pc-solaris2.11 and
> sparcv9-sun-solaris2.11.  Initially, gdb.base/attach.exp seemed to
> regress on 32-bit Solaris/SPARC, but that turned out to be due to
> flakyness of parts of the testsuite on Solaris.
>
>> In the meantime, I have a trivial coding style comment:
>>
>>> 
>>> diff --git a/gdb/procfs.c b/gdb/procfs.c
>>> index 7b7ff45..7cd870c 100644
>>> --- a/gdb/procfs.c
>>> +++ b/gdb/procfs.c
>>> @@ -913,7 +913,12 @@ proc_wait_for_stop (procinfo *pi)
>>> 
>>>      procfs_ctl_t cmd = PCWSTOP;
>>> 
>>> +    /* PR gdb/8527
>>> +     * Was not correctly interrupting the inferior process
>>> +     * when ^C was pressed in the debug terminal.
>>> +     */
>>
>> For multiline comments like the above, we do not repeat the '*'
>> at the beginning of each line. 
>>
>>        /* PR gdb/8527: Was not correctly interrupting the inferior process
>>           when ^C was pressed in the debug terminal.  */
>>
>> And if I may, reading this sentence, it's a bit hard to understand
>> what the comment is trying to explain. The following might be
>> a little more precise:
>>
>>        /* PR gdb/8527: Call set_sigint_trap to make sure that a ctrl-c
>>           pressed in the debugger terminal gets passed down to the
>>           inferior, thus causing it to be interrupted.  */
>
> TBH, I'd just leave off the comments: this is just what
> set_sigint_trap/clear_sigint_trap are supposed to do.  No other use
> comments on this, and the PR reference can easily be found in the commit
> message and the ChangeLog.
>
>>> +    set_sigint_trap();
>
> Another nit: blank before (), here and below.
>
>>>      win = (write (pi->ctl_fd, (char *) &cmd, sizeof (cmd)) == sizeof (cmd));
>>> +
>>> +    /* PR gdb/8527 */
>>> +    clear_sigint_trap();
>>> +
>>>      /* We been runnin' and we stopped -- need to update status.  */
>>>      pi->status_valid = 0;
>
> When I noticed that we don't have any test for this issue, I started to
> develop one.  This turned out to be a rough trip and my first foray into
> the gdb testsuite, so please bear with me.
>
> Looking for possible testcases to modify, I first came
> gdb.base/interrupt-daemon.exp.  However, there turned out to be two
> issues: I'd needed the pid of the grandchild process to attach to, and
> this wasn't emitted to gdb.log when printed.
>
> Besides, when I checked the test as is, it already FAILs on Solaris.
> This seems to happen because set follow-fork-mode child isn't
> implemented, but fails silently and the list of targets supporting it is
> is either incomplete or completely missing in the tests that use it.
>
> Next, I started with a copy of gdb.base/random-signal.c, adding a call
> to setpgrp to detach it from its controling terminal.
>
> Initially, that test FAILed, too, because it expected a
>
> 	Program received signal SIGINT.*
>
> message while on Solaris I get
>
> 	Thread N received signal SIGINT.*
>
> I suppose that's because starting with Solaris 10, every process is
> multithreaded.  Once I allowed for that form, too, the test PASSed on
> Solaris, both for the run and attach cases.  I'll go through the
> testsuite and allow for both cases there, too, probably causing several
> tests to magically PASS now ;-)
>
> As expected, with unmodified gdb, I get the expected
>
> FAIL: gdb.base/signal-no-ctty.exp: attach: stop with control-c (timeout)
>
> However, when I tested the testcase on Linux/x86_64, it FAILs:
>
> attach 113292
> Attaching to program:
> /vol/gcc/obj/gdb/gdb/dist/gdb/testsuite/outputs/gdb.base/signal-no-ctty/signal-no-ctty,
> process 113292
> warning: process 113292 is a zombie - the process has already terminated
> ptrace: Operation not permitted.
> (gdb) FAIL: gdb.base/signal-no-ctty.exp: attach: attach
>
> The weird thing is that both with the setpgrp call and when run like
>
> $ ./signal-no-ctty < /dev/null >& /dev/null &
>
> ps still shows a controlling terminal for the process.  Don't yet know
> what's going on here.
>
> Current patch attached for reference.

I never got a reply to this one, but I think I just figured out the
testcase part myself.  Tested on amd64-pc-solaris2.11 and
sparcv9-sun-solaris2.11 (test fails before with

FAIL: gdb.base/signal-no-ctty.exp: child: stop with control-c (timeout)

and passes after) and x86_64-pc-linux-gnu.

Ok for master?

	Rainer

-- 
-----------------------------------------------------------------------------
Rainer Orth, Center for Biotechnology, Bielefeld University


2018-08-07  Brian Vandenberg  <phantall@gmail.com>
	    Rainer Orth  <ro@CeBiTec.Uni-Bielefeld.DE>

	gdb:
	PR gdb/8527
	* procfs.c (proc_wait_for_stop): Wrap write of PCWSTOP in
	set_sigint_trap, clear_sigint_trap.

	gdb/testsuite:
	PR gdb/8527
	* gdb.base/sigint-no-ctty.c, gdb.base/sigint-no-ctty.exp: New
	test.

# HG changeset patch
# Parent  14950de898700dec7316fb3a5691413d651ddf42
Can't interrupt process without controlling terminal on Solaris (PR gdb/8527)

2018-08-07  Brian Vandenberg  <phantall@gmail.com>

	gdb:
	PR gdb/8527
	* procfs.c (proc_wait_for_stop): Wrap write of PCWSTOP in
	set_sigint_trap, clear_sigint_trap.

	gdb/testsuite:
	PR gdb/8527
	* gdb.base/sigint-no-ctty.c, gdb.base/sigint-no-ctty.exp: New
	test.

diff --git a/gdb/procfs.c b/gdb/procfs.c
--- a/gdb/procfs.c
+++ b/gdb/procfs.c
@@ -909,7 +909,12 @@ proc_wait_for_stop (procinfo *pi)
 
   procfs_ctl_t cmd = PCWSTOP;
 
+  set_sigint_trap ();
+
   win = (write (pi->ctl_fd, (char *) &cmd, sizeof (cmd)) == sizeof (cmd));
+
+  clear_sigint_trap ();
+
   /* We been runnin' and we stopped -- need to update status.  */
   pi->status_valid = 0;
 
diff --git a/gdb/testsuite/gdb.base/sigint-no-ctty.c b/gdb/testsuite/gdb.base/sigint-no-ctty.c
new file mode 100644
--- /dev/null
+++ b/gdb/testsuite/gdb.base/sigint-no-ctty.c
@@ -0,0 +1,61 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2017-2019 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/>.  */
+
+#include <stdlib.h>
+#include <unistd.h>
+
+/* GDB reads this to figure out the child's PID.  */
+pid_t child_pid;
+
+void
+marker (void)
+{
+}
+
+int
+main ()
+{
+  /* Don't let the test case run forever.  */
+  alarm (60);
+
+  child_pid = fork ();
+
+  switch (child_pid)
+    {
+    case -1:
+      return 1;
+
+    case 0:
+      break;
+
+    default:
+      while (1)
+	{
+	  marker ();
+	  usleep (1000);
+	}
+    }
+
+  /* Detach from controlling terminal.  */
+  if (setsid () == (pid_t) -1)
+    return 1;
+
+  for (;;)
+    ;
+
+  return 0;
+}
diff --git a/gdb/testsuite/gdb.base/sigint-no-ctty.exp b/gdb/testsuite/gdb.base/sigint-no-ctty.exp
new file mode 100644
--- /dev/null
+++ b/gdb/testsuite/gdb.base/sigint-no-ctty.exp
@@ -0,0 +1,87 @@
+# Copyright 2019 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/>.  */
+
+if [target_info exists gdb,nosignals] {
+    verbose "Skipping signal-no-ctty.exp because of nosignals."
+    continue
+}
+
+# This test requires sending ^C to interrupt the running target.
+if [target_info exists gdb,nointerrupts] {
+    verbose "Skipping signal-no-ctty.exp because of nointerrupts."
+    return
+}
+
+standard_testfile
+
+if { [build_executable ${testfile}.exp ${testfile} $srcfile {debug}] == -1 } {
+    return -1
+}
+
+proc do_test {} {
+    global binfile
+    global decimal
+
+    set test_spawn_id [spawn_wait_for_attach $binfile]
+    set parent_pid [spawn_id_get_pid $test_spawn_id]
+
+    # Attach to the parent, run it to a known point, extract the
+    # child's PID, and detach.
+    with_test_prefix "parent" {
+	clean_restart ${binfile}
+
+	gdb_test "attach $parent_pid" \
+	    "Attaching to program.*, process $parent_pid.*" \
+	    "attach"
+
+	gdb_breakpoint "marker"
+	gdb_continue_to_breakpoint "marker"
+
+	set child_pid [get_integer_valueof "child_pid" -1]
+	if {$child_pid == -1} {
+	    return
+	}
+
+	gdb_test "detach" \
+	    "Detaching from program: .*process $parent_pid\r\n\\\[Inferior $decimal \\(.*\\) detached\\\]"
+
+	remote_exec host "kill -9 $parent_pid"
+    }
+
+    # Start over, and attach to the child this time.
+    with_test_prefix "child" {
+	global gdb_prompt
+
+	clean_restart $binfile
+
+	gdb_test "attach $child_pid" \
+	    "Attaching to program.*, process $child_pid.*" \
+	    "attach"
+
+	gdb_test_multiple "continue" "continue" {
+	    -re "Continuing" {
+		pass "continue"
+	    }
+	}
+
+	after 500 {send_gdb "\003"}
+	gdb_test "" "(Program|Thread .*) received signal SIGINT.*" \
+	    "stop with control-c"
+
+	remote_exec host "kill -9 $child_pid"
+    }
+}
+
+do_test