ada/9480: Cannot "kill -TERM" programs that link the tasking runtime [GNAT]
Craig Carey
research@ijs.co.nz
Sun Feb 2 14:27:00 GMT 2003
Description of Problem in GNAT:
Three extra threads show up when no new tasks are added but there is only an
added "9.7.2 Timed Entry Call[s]" that unblocks the delay statement if the
program is being closed. I refer here to the difference between "Version 1"
and "Version 2" of the program that shows what happens when the TERM signal
is sent to the program.
Background:
A bug report was sent to the GCC bug report system. This message informs
ACT of the new detail of how 3 of the 4 threads can't be terminated with a
TERM signal, in both Linux and FreeBSD's Linux emulator.
http://gcc.gnu.org/cgi-bin/gnatsweb.pl
Here are some test results that confirm that the reported problem in Linux
existed. A way to get around the problem in GNAT 3.15p Ada (see source
code below) removes the problem for GNAT's FSU threads. For the GNAT Native
Linux threads, what was 1 thread is then replaced with 4, the program will
catch a TERM signal if it is applied to one of the lesser threads of the
four.
Method of shutting the program down:
"KILL": kill -s TERM <pid>
"TERM": kill -s KILL <pid>
--------------------------------------------------------------------------------
Version 1 of the program:
This is the program shown in bug report 9480 that was sent to the GCC website.
The program does not have an Ada TERM-signal Interrupt handler.
Tests 1,2:
OS=Linux & FreeBSD, Linux 3.15p with FSU threads :
TERM Is ignored. (In the corresponding case with the FreeBSD 3.15p compiler,
the TERM signal is not ignored.) KILL Kills OK.
Tests 3,4:
OS=Linux & FreeBSD, Linux 3.15p with Native threads :
TERM is Ignored. KILL Kills. (One thread shows in 'top'.)
Test 5:
OS=FreeBSD, Executable created by FreeBSD v3.15p Port :
TERM terminates. KILL Kills.
--------------------------------------------------------------------------------
Version 2 of the program:
Version 2 appears below.
Tests 6,7:
OS=Linux & FreeBSD, Linux 3.15p with FSU threads : TERM terminates. KILL kills.
Tests 8,9:
OS=Linux & FreeBSD, Linux 3.15p with Native threads :
TERM: Handled OK by 1 of the 4 threads and ignored by the other 3 threads.
KILL: The program stops with a KILL signal to any of the 4 threads.
Test 10:
OS=FreeBSD, Executable created by FreeBSD Port of the GNAT v3.15p Ada 95
compiler:
TERM: handled OK in Ada OK. KILL Kills.
--------------------------------------------------------------------------------
Other information about the testing done:
* "OS" is an abbreviation for 'operating system'.
* The Linux was Debian Linux, kernel version 2.4.20. The FreeBSD was v4.7.
* The compilers were ACT's 3.15p compiler rather than the GCC Ada compiler.
Here is version 2 of the program that will stop OK when a "kill -s TERM" is
done, but only if one of the four threads is the target of the signal.
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------
with Ada.Text_IO;
with Sigterm_Ignored;
procedure Sigterm_Ignored_2 is
package Tio renames Ada.Text_IO;
package S renames Sigterm_Ignored;
task type Freerun;
task body Freerun is
begin
null;
end Freerun;
Ans : Boolean;
begin
loop
Tio.Put_Line ("Delaying");
select
S.Signals.Shutdown;
exit;
or
delay 1.3;
end select;
end loop;
S.Signals.Interrupt_Was_Received (Ans => Ans);
Tio.Put_Line ("Quitting. Interrupt was received = " &
Boolean'Image (Ans));
end Sigterm_Ignored_2;
-------------------------------------------------------------------------------
with Ada.Interrupts.Names;
package Sigterm_Ignored is
protected Signals is
procedure SIGTERM_Handler;
pragma Interrupt_Handler (SIGTERM_Handler);
pragma Attach_Handler (SIGTERM_Handler, Ada.Interrupts.Names.SIGTERM);
entry Shutdown;
procedure Interrupt_Was_Received (Ans : out Boolean);
private
Unblocked : Boolean := False;
end Signals;
end Sigterm_Ignored;
-------------------------------------------------------------------------------
package body Sigterm_Ignored is
protected body Signals is
procedure SIGTERM_Handler is
begin
Unblocked := True;
end SIGTERM_Handler;
entry Shutdown
when Unblocked is
begin
null;
end Shutdown;
procedure Interrupt_Was_Received (Ans : out Boolean) is
begin
Ans := Unblocked;
end Interrupt_Was_Received;
end Signals;
end Sigterm_Ignored;
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------
>From: okellogg@freenet.de (Oliver Kellogg)
>Newsgroups: comp.lang.ada
>Subject: tasking programs built with GNAT insensitive to SIGTERM
>Date: 29 Jan 2003 07:04:07 -0800
>Organization: http://groups.google.com/
>Lines: 16
>Message-ID: <6a6390b8.0301290704.7880bb16@posting.google.com>
>NNTP-Posting-Date: 29 Jan 2003 15:04:07 GMT
>
>Hi,
>
>Under Linux, how come tasking programs built with GNAT
>(3.2, but other versions as well) don't react to
>"kill -TERM" ?
>
>Is there a trick to make them killable?
>
>See also http://gcc.gnu.org/cgi-bin/gnatsweb.pl,
>bug number 9480.
>
>Thanks,
>
>Oliver
>
>-- okellogg at freenet dot de
Below, inside this bug/problem report to the GCC GNU bug reporting system
and webpage, is the program I named "Version 1" (in some text above).
A page under http://gcc.gnu.org/cgi-bin/gnatsweb.pl :
| View Problem Report: 9480
|
| or send email to interested parties
|
| --------------------------------------------------------------------------------
| Reporter's email: oliver.kellogg@sysde.eads.net
| CC these people
| on PR status email:
|
| Number: 9480
| Category: ada
| Synopsis: Cannot "kill -TERM" programs that link the tasking runtime
| Confidential: no
| Severity: serious
| Priority: medium
| Responsible: unassigned
| State: open
| Class: sw-bug
| Submitter-Id: net
| Arrival-Date: Tue Jan 28 15:06:01 UTC 2003
| Closed-Date:
| Last-Modified:
| Originator: Oliver M. Kellogg
| Release: gcc-3.2.1
| Organization:
| Environment: RedHat Linux 8.0 (i686)
|
| Description: A main program that merely contains a task type
| declaration (but no task object) does not react to
| the TERM signal.
| OTOH, A main program without any tasking related
| declarations reacts normally to the SIGTERM.
|
| Here is the test program:
|
| -- file: sigterm_ignored.adb
| with Text_Io;
|
| procedure Sigterm_Ignored is
|
| task type Freerun;
| -- NB: Only a task TYPE, not even a real task.
| task body Freerun is
| begin
| null;
| end Freerun;
|
| begin
| loop
| text_io.put_line ("Here is the main program.");
| delay 1.3;
| end loop;
| end Sigterm_Ignored;
|
| File Attachments:
| How-To-Repeat: gnatmake the test program and start it.
| Then try doing a "kill -TERM" on the process and witness
| that the program is not terminated.
|
| Fix:
|
| Release-Note:
| Unformatted:
|
| --------------------------------------------------------------------------------
|
| or send email to interested parties
|
| Audit Trail:
|
----
Note: if this is rejected by the GNAT problem report handling system of ACT
then I most likely would not renew the document and resend it.
Craig Carey
New Zealand
More information about the Gcc-bugs
mailing list