Re: [patch] Single stepping over atomic instruction sets for GDB 6.6

[Jan Kratochvil <jan.kratochvil@redhat.com>]

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On Mon, 23 Apr 2007 20:19:31 +0200, Luis Machado wrote:
...
> This is the patch for handling the sigle stepping of atomic instruction
> sets previously posted on this list refreshed for the stable version 6.6
> of GDB, in case users of this version would like to use it.

It fails for me on the attached testcase on gdb-6.6.ppc64 in 99% cases with
	infrun.c:1567: internal-error: handle_inferior_event: Assertion `SOFTWARE_SINGLE_STEP_P () && singlestep_breakpoints_inserted_p' failed.
	(tested on 4x CPU POWER5+, kernel-2.6.18-8.1.1.el5.ppc64)

The attached patch ON TOP OF YOURS fixes this problem (mostly, see below).

This patch has not been ported to HEAD as the last CVS version of your patch
I found is
	http://sourceware.org/ml/gdb-patches/2007-03/msg00145.html
which is no longer applicable to HEAD, please update it.

--

This fix is not 100%, though, it now passes only in 93% cases, in the remaining
7% of cases it will prematurely FAIL due to (missed breakpoint)
	Program exited normally.

I believe it is not a failure of this fix but some unrelated PPC port problem.
Unfortunately this "Program exited normally." FAIL becomes unreproducible while
trying to debug it (`set debug infrun 1'), there is some race.


Regards,
Jan

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2007-04-28  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* infrun.c (handle_inferior_event): Handle
	(STEPPING_PAST_SINGLESTEP_BREAKPOINT
	 && !SINGLESTEP_BREAKPOINTS_INSERTED_P).

2007-04-28  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* gdb.threads/atomic-step-mass-join.c,
	gdb.threads/atomic-step-mass-join.exp: New files.

diff -u -rup gdb-6.6-orig/gdb/infrun.c gdb-6.6/gdb/infrun.c
--- gdb-6.6-orig/gdb/infrun.c	2006-10-18 18:56:13.000000000 +0200
+++ gdb-6.6/gdb/infrun.c	2007-04-28 19:23:08.000000000 +0200
@@ -1561,10 +1561,17 @@ handle_inferior_event (struct execution_
 
   if (stepping_past_singlestep_breakpoint)
     {
-      gdb_assert (SOFTWARE_SINGLE_STEP_P ()
-		  && singlestep_breakpoints_inserted_p);
-      gdb_assert (ptid_equal (singlestep_ptid, ecs->ptid));
-      gdb_assert (!ptid_equal (singlestep_ptid, saved_singlestep_ptid));
+      gdb_assert (SOFTWARE_SINGLE_STEP_P ());
+      /* SINGLESTEP_BREAKPOINTS_INSERTED_P is 0 if the another thread which hit
+	 the singlestep breakpoint intended for SAVED_SINGLESTEP_PTID is not
+	 right now at the atomic sequence.  SINGLESTEP_PTID is not defined in
+	 such case.  SINGLESTEP_BREAKPOINTS_INSERTED_P is 1 when both the
+	 SAVED_SINGLESTEP_PTID thread and the SINGLESTEP_PTID thread skip over
+	 an atomic sequence, possibly a different one.  */
+      gdb_assert (!singlestep_breakpoints_inserted_p
+		  || ptid_equal (singlestep_ptid, ecs->ptid));
+      gdb_assert (!singlestep_breakpoints_inserted_p
+		  || !ptid_equal (singlestep_ptid, saved_singlestep_ptid));
 
       stepping_past_singlestep_breakpoint = 0;
 
@@ -1575,9 +1582,13 @@ handle_inferior_event (struct execution_
 	{
 	  if (debug_infrun)
 	    fprintf_unfiltered (gdb_stdlog, "infrun: stepping_past_singlestep_breakpoint\n");
-	  /* Pull the single step breakpoints out of the target.  */
-	  (void) SOFTWARE_SINGLE_STEP (0, 0);
-	  singlestep_breakpoints_inserted_p = 0;
+
+	  if (singlestep_breakpoints_inserted_p)
+	    {
+	      /* Pull the single step breakpoints out of the target.  */
+	      (void) SOFTWARE_SINGLE_STEP (0, 0);
+	      singlestep_breakpoints_inserted_p = 0;
+	    }
 
 	  ecs->random_signal = 0;
 
diff -u -rup gdb-6.6-orig/gdb/testsuite/gdb.threads/atomic-step-mass-join.c gdb-6.6/gdb/testsuite/gdb.threads/atomic-step-mass-join.c
--- gdb-6.6-orig/gdb/testsuite/gdb.threads/atomic-step-mass-join.c	2007-04-28 19:43:46.000000000 +0200
+++ gdb-6.6/gdb/testsuite/gdb.threads/atomic-step-mass-join.c	2007-04-28 19:24:15.000000000 +0200
@@ -0,0 +1,57 @@
+/* Test case for stepping over RISC atomic code constructs.
+
+   Copyright 2007
+   free software foundation, inc.
+
+   This file is part of GDB.
+
+   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.  */
+
+#include <pthread.h>
+#include <assert.h>
+#include <unistd.h>
+
+static volatile int var;
+
+static void *start (void *arg)
+{
+  /* Do not start quitting before all the threads were spawn.  */
+  sleep (5);
+
+  return arg;
+}
+
+#define LENGTH(x) (sizeof (x) / sizeof (x)[0])
+
+int main (void)
+{
+  pthread_t thread[20];
+  int i, j;
+
+  var = 0;
+  for (j = 0; j < LENGTH (thread); j++)
+    {
+      i = pthread_create (&thread[j], NULL, start, NULL);	/* _create_ */
+      assert (i == 0);
+    }
+  for (j = 0; j < LENGTH (thread); j++)
+    {
+      i = pthread_join (thread[j], NULL);			/* _delete_ */
+      assert (i == 0);
+    }
+
+  return 0;	/* _quit_ */
+}
diff -u -rup gdb-6.6-orig/gdb/testsuite/gdb.threads/atomic-step-mass-join.exp gdb-6.6/gdb/testsuite/gdb.threads/atomic-step-mass-join.exp
--- gdb-6.6-orig/gdb/testsuite/gdb.threads/atomic-step-mass-join.exp	2007-04-28 19:43:46.000000000 +0200
+++ gdb-6.6/gdb/testsuite/gdb.threads/atomic-step-mass-join.exp	2007-04-28 19:42:25.000000000 +0200
@@ -0,0 +1,93 @@
+# atomic-step-mass-join.exp -- Test case for stepping over RISC atomic code constructs.
+# Copyright (C) 2007 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
+
+set testfile atomic-step-mass-join
+set srcfile ${testfile}.c
+set binfile ${objdir}/${subdir}/${testfile}
+
+if [istarget "*-*-linux"] then {
+    set target_cflags "-D_MIT_POSIX_THREADS"
+} else {
+    set target_cflags ""
+}
+
+if {[gdb_compile_pthreads "${srcdir}/${subdir}/${srcfile}" "${binfile}" executable {debug}] != "" } {
+    return -1
+}
+
+gdb_exit
+gdb_start
+gdb_reinitialize_dir $srcdir/$subdir
+
+gdb_load ${binfile}
+if ![runto_main] then {
+   fail "Can't run to main"
+   return 0
+}
+
+# With a watchpoint we would crash on pthread_create(3):
+# 	Program received signal SIGSTOP, Stopped (signal).
+# 	[Switching to Thread 4160681152 (LWP 979)]
+# 	0x0f55c368 in clone () from /lib/libc.so.6
+# Still it is not applicable so far due to:
+# 	[New Thread 4139709632 (LWP 9022)]^M
+# 	0x0f354a28 in __nptl_create_event () from /lib/libpthread.so.0^M
+# 	ptrace: No such process.^M
+#gdb_test "handle SIGSTOP nostop noprint pass"			\
+#	 ".*SIGSTOP +No\tNo\tYes\t+Stopped \\(signal\\)"	\
+#	 "Disown SIGSTOP"
+
+set line [gdb_get_line_number "_delete_"]
+gdb_test "tbreak $line" \
+	 "Breakpoint (\[0-9\]+) at .*$srcfile, line $line\..*" \
+	 "set breakpoint at delete"
+gdb_test "c" \
+	 ".*/\\* _delete_ \\*/.*" \
+	 "run till _delete_"
+
+# Without a software watchpoint no single-stepping would be used.
+set test "Start (software) watchpoint"
+gdb_test_multiple "watch var" $test {
+    -re "Watchpoint \[0-9\]+: var.*$gdb_prompt $" {
+	pass $test
+    }
+    -re "Hardware watchpoint \[0-9\]+: var.*$gdb_prompt $" {
+	# We do not test the goal but still the whole testcase should pass.
+	unsupported $test
+    }
+}
+
+###gdb_test "set debug infrun 1" ""
+
+set line [gdb_get_line_number "_quit_"]
+gdb_test "tbreak $line" \
+	 "Breakpoint \[0-9\]+ at .*$srcfile, line $line\..*" \
+	 "set breakpoint at _quit_"
+set timeout_old $timeout
+# 20 threads may take about 45 seconds.  */
+set timeout 180
+gdb_test "c" \
+	 ".*/\\* _quit_ \\*/.*" \
+	 "run till _quit_"
+set timeout $timeout_old
+
+gdb_test "c" \
+	 ".*Program exited normally\\." \
+	 "run till program exit"