Re: [patch] New thread test to exercise Daniel's Patch

[Jeff Johnston <jjohnstn@redhat.com>]

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Jeff Johnston wrote:
> Daniel Jacobowitz wrote:
> 
>> On Thu, Mar 25, 2004 at 03:22:13PM -0500, Jeff Johnston wrote:
>>
>>> Daniel Jacobowitz wrote:
>>>
>>>> On Wed, Mar 24, 2004 at 11:39:50PM -0500, Daniel Jacobowitz wrote:
>>>>
>>>>
>>>>> Do you have any code for PTRACE_EVENT_CLONE yet, or should I put
>>>>> something together in the morning to verify whether that's the 
>>>>> problem?
>>>>
>>>>
>>>>
>>>> Here you go.  Again, this patch is obviously not ready to go into GDB,
>>>> but I have not been able to make it misbehave yet.  I don't know if all
>>>> the bits it needs work right in RHEL3, or if my testing was conclusive.
>>>>
>>>> The highlights:
>>>> - Includes most of the previous patch
>>>> - Uses PTRACE_EVENT_CLONE to attach to new threads
>>>> - Moves handling of events closer to the waitpid call
>>>>
>>>> There are some potential races but I haven't hit any of them in
>>>> practice.  I suspect that with a heavy fork or vfork load (not clone)
>>>> you could produce interesting failure modes.
>>>>
>>>> Give it a try, please.  If it works I'll clean it up.
>>>>
>>>
>>> Works great.  I was unable to get it to misbehave on RHEL3.  Please 
>>> go ahead cleaning it up.
>>
>>
>>
>> Here's the final patch. The description of the patch is unchanged from
>> the above.  The background, for those who did not read the whole
>> discussion: in NPTL, a signal delivered to the process when any thread
>> is not attached is likely to terminate the process.  So we need to be
>> careful to:
>>  - know when threads have exited, so that we can attach to new threads
>>    which reuse the same thread ID
>>  - attach to threads as early as possible
>>
>> Both of these could cause problems in LinuxThreads, but they were less
>> drastic.
>>
>> Tested with both LinuxThreads and NPTL.  I'll commit this to HEAD on
>> Monday, barring objections.  We've missed the boat for GDB 6.1 at this
>> point.
>>
>> The testcase you posted has credits in it, so we can't just grab it for
>> the testsuite.  But all we should need to test this is a loop that
>> creates short-lived threads, and then verifying that we can send C-c,
>> get a prompt, issue info threads, and continue a couple of times
>> without seeing anyting matching "error:".  Interested in writing that
>> test? :)
>>
> 
> Sure.  Just tried debugging eclipse today with this patch applied and it 
> works as well.
> 
> -- Jeff J.
> 
> 

See the attached test.  There was some stuff in pthreads.exp about Crtl-C and 
alpha-*-osf*.  Do I need to account for this platform?

2004-03-26  Jeff Johnston  <jjohnstn@redhat.com>

         * gdb.threads/manythreads.c: New testcase.
         * gdb.threads/manythreads.exp: Ditto.


-- Jeff J.

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Index: manythreads.exp
===================================================================
RCS file: manythreads.exp
diff -N manythreads.exp
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ manythreads.exp	26 Mar 2004 21:03:17 -0000
@@ -0,0 +1,116 @@
+# manythreads.exp -- Expect script to test stopping many threads
+# Copyright (C) 2004 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 2 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, write to the Free Software
+# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  
+
+# Please email any bugs, comments, and/or additions to this file to:
+# bug-gdb@prep.ai.mit.edu
+
+# This file was written by Jeff Johnston. (jjohnstn@redhat.com)
+
+if $tracelevel then {
+	strace $tracelevel
+}
+
+set prms_id 0
+set bug_id 0
+
+# This only works with native configurations
+if ![isnative] then {
+    return
+}
+
+set testfile "manythreads"
+set srcfile ${testfile}.c
+set binfile ${objdir}/${subdir}/${testfile}
+if {[gdb_compile "${srcdir}/${subdir}/${srcfile}" "${binfile}" executable {debug libs=-lpthread}] != ""} {
+    return -1
+}
+
+gdb_start
+gdb_reinitialize_dir $srcdir/$subdir
+gdb_load ${binfile}
+send_gdb "set print sevenbit-strings\n" ; gdb_expect -re "$gdb_prompt $"
+runto_main
+
+# We'll need this when we send_gdb a ^C to GDB.  Need to do it before we
+# run the program and gdb starts saving and restoring tty states.
+# On Ultrix, we don't need it and it is really slow (because shell_escape
+# doesn't use vfork).
+if ![istarget "*-*-ultrix*"] then {
+    gdb_test "shell stty intr '^C'" ""
+}
+
+send_gdb "continue\n"
+gdb_expect {
+  -re "Continuing"
+    { pass "first continue" }
+  timeout
+    { fail "first continue (timeout)" }
+}
+
+# Send a Ctrl-C and verify that we can do info threads and continue
+after 100 {send_gdb "\003"}
+gdb_expect {
+  -re "Program received signal SIGINT.*$gdb_prompt $"
+    {
+      pass "stop threads"
+    }
+  timeout
+    {
+      fail "stop threads (timeout)"
+    }
+} 
+
+gdb_test "info threads" ".*1 Thread.*.LWP.*"
+
+send_gdb "continue\n"
+gdb_expect {
+  -re "Continuing"
+    { pass "second continue" }
+  timeout
+    { fail "second continue (timeout)" }
+}
+
+# Send another Ctrl-C and verify that we can do info threads and quit
+after 100 {send_gdb "\003"}
+gdb_expect {
+  -re "Program received signal SIGINT.*$gdb_prompt $"
+    {
+      pass "stop threads"
+    }
+  timeout
+    {
+      fail "stop threads (timeout)"
+    }
+} 
+
+send_gdb "quit\n"
+gdb_expect {
+    -re "The program is running.  Exit anyway\\? \\(y or n\\) $" {
+        send_gdb "y\n"
+        exp_continue
+    }
+    eof {
+        pass "GDB exits after stopping multithreaded program"
+    }
+    default {
+        fail "GDB exits after stopping multithreaded program"
+    }
+    timeout {
+        fail "GDB exits after stopping multithreaded program (timeout)"
+    }
+}
+
Index: manythreads.c
===================================================================
RCS file: manythreads.c
diff -N manythreads.c
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ manythreads.c	26 Mar 2004 21:03:17 -0000
@@ -0,0 +1,42 @@
+#include <pthread.h>
+#include <stdio.h>
+
+void *
+thread_function (void *arg)
+{
+  int x = (int)arg;
+
+  printf ("Thread <%d> executing\n", x);
+
+  return NULL;
+}
+
+int 
+main (int argc, char **argv)
+{
+  pthread_attr_t attr;
+  pthread_t threads[256];
+  int i, j;
+
+  pthread_attr_init (&attr);
+
+  /* Create a ton of quick-executing threads, then wait for them to
+     complete.  */
+  for (i = 0; i < 1000; ++i) 
+    {
+      for (j = 0; j < 256; ++j)
+	{
+	  pthread_create (&threads[j], &attr, thread_function, 
+			  (void *)(i * 1000 + j));
+	}
+
+      for (j = 0; j < 256; ++j)
+	{
+	  pthread_join (threads[j], NULL);
+	}
+    }
+
+  pthread_attr_destroy (&attr);
+
+  return 0;
+}