Blob Blame History Raw
2007-07-01  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* linux-nat.h (struct lwp_info): New field WAS_STOPPED.
	* linux-nat.c (STRINGIFY, STRINGIFY_ARG): New macros.
	(kill_lwp): New declaration.
	(linux_ptrace_post_attach, pid_is_stopped): New function.
	(linux_child_follow_fork): New comment about WAS_STOPPED.
	(lin_lwp_attach_lwp): Variable PID removed.  Part replaced by a call to
	LINUX_PTRACE_POST_ATTACH.
	(linux_nat_attach): Likewise.
	(linux_nat_detach): Optionally stop the detached process.
	(linux_nat_resume): Clear WAS_STOPPED if appropriate.
	* NEWS: Document the new behaviour.

2007-06-30  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* gdb.threads/attach-into-signal.c, gdb.threads/attach-into-signal.exp,
	gdb.threads/attach-stopped.c, gdb.threads/attach-stopped.exp: New files.

2007-06-30  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* gdb.texinfo (Attach): Document the ATTACH and DETACH commands for
	stopped processes.  Document the messages on the seen pending signals.

[ Backport for GDB-6.6. ]

--- ./gdb/NEWS	21 Jun 2007 15:18:50 -0000	1.232
+++ ./gdb/NEWS	30 Jun 2007 16:27:37 -0000
@@ -44,6 +44,9 @@ segment base addresses (rather than offs
 * The /i format now outputs any trailing branch delay slot instructions 
 immediately following the last instruction within the count specified.
 
+* On GNU/Linux, stopped processes may get attached to now.  Signals being
+delivered at the time of the attach command no longer get lost.
+
 * New commands
 
 set remoteflow
--- gdb-6.6/gdb/linux-nat.c-orig-orig	2007-09-16 20:57:13.000000000 +0200
+++ gdb-6.6/gdb/linux-nat.c	2007-09-16 21:02:28.000000000 +0200
@@ -87,6 +87,12 @@
 #define __WALL          0x40000000 /* Wait for any child.  */
 #endif
 
+#define STRINGIFY_ARG(x) #x
+#define STRINGIFY(x) STRINGIFY_ARG (x)
+
+static int linux_ptrace_post_attach (struct lwp_info *lp);
+static int kill_lwp (int lwpid, int signo);
+
 /* The single-threaded native GNU/Linux target_ops.  We save a pointer for
    the use of the multi-threaded target.  */
 static struct target_ops *linux_ops;
@@ -533,6 +539,11 @@ child_follow_fork (struct target_ops *op
 	}
       else
 	{
+	  /* We should check LP->WAS_STOPPED and detach it stopped accordingly.
+	     In this point of code it cannot be 1 as we would not get FORK
+	     executed without CONTINUE first which resets LP->WAS_STOPPED.
+	     We would have to first TARGET_STOP and WAITPID it as with running
+	     inferior PTRACE_DETACH, SIGSTOP will ignore the signal.  */
 	  target_detach (NULL, 0);
 	}
 
@@ -992,7 +1003,6 @@ lin_lwp_attach_lwp (ptid_t ptid, int ver
      to happen.  */
   if (GET_LWP (ptid) != GET_PID (ptid) && lp == NULL)
     {
-      pid_t pid;
       int status;
 
       if (ptrace (PTRACE_ATTACH, GET_LWP (ptid), 0, 0) < 0)
@@ -1002,37 +1012,16 @@ lin_lwp_attach_lwp (ptid_t ptid, int ver
       if (lp == NULL)
 	lp = add_lwp (ptid);
 
-      if (debug_linux_nat)
-	fprintf_unfiltered (gdb_stdlog,
-			    "LLAL: PTRACE_ATTACH %s, 0, 0 (OK)\n",
-			    target_pid_to_str (ptid));
-
-      pid = my_waitpid (GET_LWP (ptid), &status, 0);
-      if (pid == -1 && errno == ECHILD)
-	{
-	  /* Try again with __WCLONE to check cloned processes.  */
-	  pid = my_waitpid (GET_LWP (ptid), &status, __WCLONE);
-	  if (pid == -1 && errno == ECHILD)
-	    error (_("Can't attach %s (%s) - possible SELinux denial,"
-		     " check your /var/log/messages for `avc: denied'"),
-		   target_pid_to_str (ptid), safe_strerror (errno));
-	  lp->cloned = 1;
+      status = linux_ptrace_post_attach (lp);
+      if (status != 0)
+        {
+	  error (_("Thread %s exited: %s"), target_pid_to_str (ptid),
+		 status_to_str (status));
 	}
 
-      gdb_assert (pid == GET_LWP (ptid)
-		  && WIFSTOPPED (status) && WSTOPSIG (status));
-
-      target_post_attach (pid);
+      target_post_attach (GET_LWP (ptid));
 
       lp->stopped = 1;
-
-      if (debug_linux_nat)
-	{
-	  fprintf_unfiltered (gdb_stdlog,
-			      "LLAL: waitpid %s received %s\n",
-			      target_pid_to_str (ptid),
-			      status_to_str (status));
-	}
     }
   else
     {
@@ -1061,11 +1049,172 @@ lin_lwp_attach_lwp (ptid_t ptid, int ver
   return 0;
 }
 
+/* Detect `T (stopped)' in `/proc/PID/status'.
+   Other states including `T (tracing stop)' are reported as false.  */
+
+static int
+pid_is_stopped (pid_t pid)
+{
+  FILE *status_file;
+  char buf[100]; 
+  int retval = 0;
+
+  snprintf (buf, sizeof (buf), "/proc/%d/status", (int) pid);
+  status_file = fopen (buf, "r");
+  if (status_file != NULL)
+    {
+      int have_state = 0;
+
+      while (fgets (buf, sizeof (buf), status_file))
+	{
+	  if (strncmp (buf, "State:", 6) == 0)
+	    {
+	      have_state = 1;
+	      break;
+	    }
+	} 
+      if (have_state && strstr (buf, "T (stopped)") != NULL)
+	retval = 1;
+      fclose (status_file);
+    }
+  return retval;
+}
+
+/* Handle the processing after PTRACE_ATTACH, the first WAITPID -> SIGSTOP.
+   Returns STATUS if the thread has exited, 0 otherwise.
+   Sets LP->WAS_STOPPED if the process was originally stopped.
+   Sets LP->CLONED if the given LWP is not the thread leader.
+
+   Scenario for a standard unstopped inferior:
+    * `S (sleeping)' or `R (running)' or similiar states.
+    * PTRACE_ATTACH is called.
+    * `S (sleeping)' (or similiar) for some while.
+    * `T (tracing stop)'.
+    * WAITPID succeeds here returning SIGSTOP (signalled by PTRACE_ATTACH).
+
+   Scenario for a formerly stopped inferior:
+    * `T (stopped)'.
+    * PTRACE_ATTACH is called.
+    * `T (stopped)' would stay indefinitely
+      Note since this moment the `TracerPid' field gets filled
+      (by PTRACE_ATTACH), it is no longer just the common `T (stopped)' state.
+       * If no one did WAITPID since sending SIGSTOP our WAITPID would return
+         SIGSTOP.  The state still would not turn to `T (tracing stop)'.
+       * Usually its original parent (before PTRACE_ATTACH was applied) already
+         did WAITPID.  The original parent already received our SIGSTOP
+         sinalled by our PTRACE_ATTACH.
+         In this case our own WAITPID would hang.  Therefore...
+    * ... we do artificial: tkill (SIGCONT);
+      `PTRACE_CONT, SIGSTOP' does not work in 100% cases as sometimes SIGSTOP
+      gets remembered by kernel during the first PTRACE_CONT later and we get
+      spurious SIGSTOP event.  Expecting the signal may get delivered to
+      a different task of the thread group.
+      `kill_lwp (SIGSTOP)' has no effect in this moment (it is already stopped).
+    * WAITPID returns the artifical SIGCONT.
+      (The possibly pending SIGSTOP gets vanished by specifically SIGCONT.)
+    * State turns `T (tracing stop)'.
+   In this moment everything is almost fine but we need a workaround as final
+   `PTRACE_DETACH, SIGSTOP' would leave the process unstopped otherwise:
+    * tkill (SIGSTOP);
+    * `PTRACE_CONT, 0'
+    * WAITPID returns the artifical SIGSTOP.
+
+   With the pending (unwaited for) SIGSTOP the artifical signal effects are:
+   kill (SIGSTOP)
+   PTRACE_ATTACH
+    /-tkill (SIGCONT), WAITPID: SIGCONT, WAITPID: hang !
+   //-tkill (SIGCONT), WAITPID: SIGCONT, PTRACE_CONT (SIG_0), WAITPID: wait (OK)
+   \\-tkill (SIGALRM), WAITPID: SIGSTOP, WAITPID: hang !
+    \-tkill (SIGALRM), WAITPID: SIGSTOP, PTRACE_CONT (SIG_0), WAITPID: SIGALRM !
+   Therefore we signal artifical SIGCONT and stop waiting after its reception.
+
+   For the detection whether the process was formerly stopped we need to
+   read `/proc/PID/status'.  `PTRACE_CONT, SIGSTOP' returns ESRCH
+   for `S (sleeping)' and succeeds for `T (stopped)' but it unfortunately
+   succeeds even for `T (tracing stop)'.  Depending on PTRACE_CONT, SIGSTOP
+   success value for formerly stopped processes would mean a race condition
+   as we would get false stopped processes detection if we get too slow.
+
+   `waitid (..., WSTOPPED)' hangs the same way as WAITPID.
+
+   Signals get queued for WAITPID.  PTRACE_ATTACH (or TKILL) enqueues SIGSTOP
+   there but WAITPID may return an already pending signal.
+   Redeliver it by PTRACE_CONT, SIGxxx as otherwise it would get lost.
+   Similiar processing is being done in this file by WAIT_LWP.  */
+
+static int
+linux_ptrace_post_attach (struct lwp_info *lp)
+{
+  ptid_t ptid = lp->ptid;
+  unsigned long sig;
+
+  if (debug_linux_nat)
+    fprintf_unfiltered (gdb_stdlog,
+			"LLAL: PTRACE_ATTACH %s, 0, 0 (OK)\n",
+			target_pid_to_str (ptid));
+
+  lp->was_stopped = pid_is_stopped (GET_LWP (ptid));
+  if (lp->was_stopped)
+    {
+      if (kill_lwp (GET_LWP (ptid), SIGCONT) != 0)
+	perror_with_name (("kill_lwp (SIGCONT)"));
+    }
+
+  for (;;)
+    {
+      pid_t pid;
+      int status;
+
+      pid = my_waitpid (GET_LWP (ptid), &status, 0);
+      if (pid == -1 && errno == ECHILD)
+	{
+	  /* Try again with __WCLONE to check cloned processes.  */
+	  pid = my_waitpid (GET_LWP (ptid), &status, __WCLONE);
+	  lp->cloned = 1;
+	}
+      gdb_assert (pid == GET_LWP (ptid));
+
+      if (debug_linux_nat)
+	{
+	  fprintf_unfiltered (gdb_stdlog,
+			      "LLAL: waitpid %s received %s\n",
+			      target_pid_to_str (ptid),
+			      status_to_str (status));
+	}
+
+      /* Check if the thread has exited.  */
+      if (WIFEXITED (status) || WIFSIGNALED (status))
+        return status;
+      gdb_assert (WIFSTOPPED (status));
+      sig = WSTOPSIG (status);
+      gdb_assert (sig != 0);
+      if (sig == SIGSTOP)
+        break;
+
+      /* As the second signal for stopped processes we send SIGSTOP.  */
+      if (lp->was_stopped && sig == SIGCONT)
+	sig = SIGSTOP;
+
+      printf_unfiltered (_("Redelivering pending %s.\n"),
+		 target_signal_to_string (target_signal_from_host (sig)));
+      if (sig == SIGSTOP)
+	{
+	  if (kill_lwp (GET_LWP (ptid), sig) != 0)
+	    perror_with_name (("kill_lwp"));
+	  /* We now must resume the inferior to get SIGSTOP delivered.  */
+	  sig = 0;
+	}
+      if (ptrace (PTRACE_CONT, GET_LWP (ptid), NULL, (void *) sig) != 0)
+	perror_with_name (("ptrace"));
+    }
+
+  return 0;
+}
+
 static void
 linux_nat_attach (char *args, int from_tty)
 {
   struct lwp_info *lp;
-  pid_t pid;
   int status;
 
   /* FIXME: We should probably accept a list of process id's, and
@@ -1076,21 +1225,12 @@ linux_nat_attach (char *args, int from_t
   inferior_ptid = BUILD_LWP (GET_PID (inferior_ptid), GET_PID (inferior_ptid));
   lp = add_lwp (inferior_ptid);
 
-  /* Make sure the initial process is stopped.  The user-level threads
-     layer might want to poke around in the inferior, and that won't
-     work if things haven't stabilized yet.  */
-  pid = my_waitpid (GET_PID (inferior_ptid), &status, 0);
-  if (pid == -1 && errno == ECHILD)
-    {
-      warning (_("%s is a cloned process"), target_pid_to_str (inferior_ptid));
-
-      /* Try again with __WCLONE to check cloned processes.  */
-      pid = my_waitpid (GET_PID (inferior_ptid), &status, __WCLONE);
-      lp->cloned = 1;
-    }
-
-  gdb_assert (pid == GET_PID (inferior_ptid)
-	      && WIFSTOPPED (status) && WSTOPSIG (status) == SIGSTOP);
+  status = linux_ptrace_post_attach (lp);
+  if (status != 0)
+    error (_("Program %s exited: %s\n"), target_pid_to_str (inferior_ptid),
+	   status_to_str (status));
+  if (lp->cloned)
+    warning (_("%s is a cloned process"), target_pid_to_str (inferior_ptid));
 
   lp->stopped = 1;
 
@@ -1099,8 +1239,8 @@ linux_nat_attach (char *args, int from_t
   lp->resumed = 1;
   if (debug_linux_nat)
     {
-      fprintf_unfiltered (gdb_stdlog,
-			  "LLA: waitpid %ld, faking SIGSTOP\n", (long) pid);
+      fprintf_unfiltered (gdb_stdlog, "LLA: waitpid %d, faking SIGSTOP\n",
+			  GET_PID (inferior_ptid));
     }
 }
 
@@ -1173,6 +1313,9 @@ linux_nat_detach (char *args, int from_t
 
   trap_ptid = null_ptid;
 
+  if (lwp_list->was_stopped)
+    args = STRINGIFY (SIGSTOP);
+
   /* Destroy LWP info; it's no longer valid.  */
   init_lwp_list ();
 
@@ -1310,6 +1453,12 @@ linux_nat_resume (ptid_t ptid, int step_
       lp->stopped = 0;
     }
 
+  /* At this point, we are going to resume the inferior and if we
+     have attached to a stopped process, we no longer should leave
+     it as stopped if the user detaches.  */
+  if (!step && lp != NULL)
+    lp->was_stopped = 0;
+
   if (resume_all)
     iterate_over_lwps (resume_callback, NULL);
 
--- ./gdb/linux-nat.h	10 May 2007 21:36:00 -0000	1.18
+++ ./gdb/linux-nat.h	29 Jun 2007 22:06:05 -0000
@@ -42,6 +42,9 @@ struct lwp_info
   /* Non-zero if this LWP is stopped.  */
   int stopped;
 
+  /* Non-zero if this LWP was stopped by SIGSTOP before attaching.  */
+  int was_stopped;
+
   /* Non-zero if this LWP will be/has been resumed.  Note that an LWP
      can be marked both as stopped and resumed at the same time.  This
      happens if we try to resume an LWP that has a wait status
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ ./gdb/testsuite/gdb.threads/attach-into-signal.c	29 Jun 2007 22:06:05 -0000
@@ -0,0 +1,70 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 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. */
+
+#include <signal.h>
+#include <unistd.h>
+#include <string.h>
+#include <stdio.h>
+#include <stdlib.h>
+#ifdef USE_THREADS
+#include <pthread.h>
+#endif
+
+void action(int sig, siginfo_t * info, void *uc)
+{
+  raise (SIGALRM);
+}
+
+static void *func (void *arg)
+{
+  struct sigaction act;
+
+  memset (&act, 0, sizeof(struct sigaction));
+  act.sa_sigaction = action;
+  act.sa_flags = SA_RESTART;
+  sigaction (SIGALRM, &act, 0);
+
+  raise (SIGALRM);
+
+  /* It is an upstream kernel bug (2.6.22-rc4-git7.x86_64, PREEMPT, SMP).
+     We never get here without ptrace(2) but we get while under ptrace(2).  */
+  for (;;)
+    pause ();
+
+  abort ();
+  /* NOTREACHED */
+  return NULL;
+}
+
+int main ()
+{
+
+#ifndef USE_THREADS
+
+  func (NULL);
+
+#else
+
+  pthread_t th;
+  pthread_create (&th, NULL, func, NULL);
+  pthread_join (th, NULL);
+
+#endif
+
+  return 0;
+}
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ ./gdb/testsuite/gdb.threads/attach-into-signal.exp	29 Jun 2007 22:06:06 -0000
@@ -0,0 +1,179 @@
+# Copyright 2007
+
+# 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.
+
+# This test was created by modifying attach-stopped.exp.
+# This file was created by Jan Kratochvil <jan.kratochvil@redhat.com>.
+
+if $tracelevel then {
+    strace $tracelevel
+}
+
+set prms_id 0
+set bug_id 0
+
+set testfile "attach-into-signal"
+set srcfile  ${testfile}.c
+set binfile  ${objdir}/${subdir}/${testfile}
+set escapedbinfile  [string_to_regexp ${objdir}/${subdir}/${testfile}]
+
+remote_exec build "rm -f ${binfile}"
+# For debugging this test
+#
+#log_user 1
+
+proc corefunc { threadtype } {
+    global srcfile
+    global binfile
+    global escapedbinfile
+    global srcdir
+    global subdir
+    global gdb_prompt
+
+    if [get_compiler_info ${binfile}] {
+	return -1
+    }
+
+    # Start the program running and then wait for a bit, to be sure
+    # that it can be attached to.
+    # Statistically there is a better chance without giving process a nice.
+
+    set testpid [eval exec $binfile &]
+    exec sleep 2
+
+    # Run 2 passes of the test.
+    # The C file inferior stops pending its signals if a single one is lost,
+    # we test successful redelivery of the caught signal by the 2nd pass.
+
+    # linux-2.6.20.4.x86_64 had maximal attempt # 20 in 4 test runs.
+    set attempts 100
+    set attempt 1
+    set passes 1
+    while { $passes < 3 && $attempt <= $attempts } {
+
+	# Start with clean gdb
+	gdb_exit
+
+	set stoppedtry 0
+	while { $stoppedtry < 10 } {
+	    if [catch {open /proc/${testpid}/status r} fileid] {
+		set stoppedtry 10
+		break
+	    }
+	    gets $fileid line1;
+	    gets $fileid line2;
+	    close $fileid;
+
+	    if {![string match "*(stopped)*" $line2]} {
+		# No PASS message as we may be looping in multiple attempts.
+		break
+	    }
+	    sleep 1
+	    set stoppedtry [expr $stoppedtry + 1]
+	}
+	if { $stoppedtry >= 10 } {
+	    verbose -log $line2
+	    set test "$threadtype: process is still running on the attempt # $attempt of $attempts"
+	    break
+	}
+
+	gdb_start
+	gdb_reinitialize_dir $srcdir/$subdir
+	gdb_load ${binfile}
+
+	# No PASS message as we may be looping in multiple attempts.
+	gdb_test "set debug lin-lwp 1" "" ""
+
+	set test "$threadtype: set file (pass $passes), before attach1 to stopped process"
+	if {[gdb_test_multiple "file $binfile" $test {
+	   -re "Load new symbol table from.*y or n. $" {
+		# No PASS message as we may be looping in multiple attempts.
+		gdb_test "y" "Reading symbols from $escapedbinfile\.\.\.*done." ""
+	    }
+	    -re "Reading symbols from $escapedbinfile\.\.\.*done.*$gdb_prompt $" {
+		# No PASS message as we may be looping in multiple attempts.
+	    }
+	}] != 0 } {
+	    break
+	}
+
+	# Main test:
+	set test "$threadtype: attach (pass $passes), pending signal catch"
+	if {[gdb_test_multiple "attach $testpid" $test {
+	    -re "Attaching to program.*`?$escapedbinfile'?, process $testpid.*Redelivering pending Alarm clock..*$gdb_prompt $" {
+		# nonthreaded:
+		pass $test
+		verbose -log "$test succeeded on the attempt # $attempt of $attempts"
+		set passes [expr $passes + 1]
+	    }
+	    -re "Attaching to program.*`?$escapedbinfile'?, process $testpid.*$gdb_prompt $" {
+		# nonthreaded:
+		# We just lack the luck, we should try it again.
+		set attempt [expr $attempt + 1]
+	    }
+	    -re "Attaching to process $testpid.*Redelivering pending Alarm clock..*$gdb_prompt $" {
+		# threaded:
+		pass $test
+		verbose -log "$test succeeded on the attempt # $attempt of $attempts"
+		set passes [expr $passes + 1]
+	    }
+	    -re "Attaching to process $testpid.*$gdb_prompt $" {
+		# threaded:
+		# We just lack the luck, we should try it again.
+		set attempt [expr $attempt - 1]
+	    }
+	}] != 0 } {
+	    break
+	}
+    }
+    if {$passes < 3} {
+	if {$attempt > $attempts} {
+	    unresolved $test
+	} else {
+	    fail $test
+	}
+    }
+
+    # Exit and detach the process.
+       
+    gdb_exit
+
+    # Make sure we don't leave a process around to confuse
+    # the next test run (and prevent the compile by keeping
+    # the text file busy), in case the "set should_exit" didn't
+    # work.
+
+    # Continue the program - some Linux kernels need it before -9 if the
+    # process is stopped.
+    remote_exec build "kill -s CONT ${testpid}"
+       
+    remote_exec build "kill -9 ${testpid}"
+}
+
+# build the test case first without threads
+#
+if  { [gdb_compile "${srcdir}/${subdir}/${srcfile}" "${binfile}" executable {debug}] != "" } {
+    gdb_suppress_entire_file "Testcase nonthraded compile failed, so all tests in this file will automatically fail."
+}
+
+corefunc nonthreaded
+
+# build the test case also with threads
+#
+if  { [gdb_compile_pthreads "${srcdir}/${subdir}/${srcfile}" "${binfile}" executable {debug additional_flags=-DUSE_THREADS}] != "" } {
+    gdb_suppress_entire_file "Testcase threaded compile failed, so all tests in this file will automatically fail."
+}
+
+corefunc threaded
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ ./gdb/testsuite/gdb.threads/attach-stopped.c	29 Jun 2007 22:06:06 -0000
@@ -0,0 +1,51 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2005-2007 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. */
+
+/* This program is intended to be started outside of gdb, then
+   manually stopped via a signal.  */
+
+#include <stddef.h>
+#include <unistd.h>
+#ifdef USE_THREADS
+#include <pthread.h>
+#endif
+
+static void *func (void *arg)
+{
+  sleep (10000);  /* Ridiculous time, but we will eventually kill it.  */
+  sleep (10000);  /* Second sleep.  */
+  return NULL;
+}
+
+int main ()
+{
+
+#ifndef USE_THREADS
+
+  func (NULL);
+
+#else
+
+  pthread_t th;
+  pthread_create (&th, NULL, func, NULL);
+  pthread_join (th, NULL);
+
+#endif
+
+  return 0;
+}
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ ./gdb/testsuite/gdb.threads/attach-stopped.exp	29 Jun 2007 22:06:06 -0000
@@ -0,0 +1,219 @@
+# Copyright 2005-2007
+
+# 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.
+
+# This test was created by modifying attach.exp.
+# This file was created by Jeff Johnston <jjohnstn@redhat.com>.
+# This file was updated by Jan Kratochvil <jan.kratochvil@redhat.com>.
+
+if $tracelevel then {
+    strace $tracelevel
+}
+
+set prms_id 0
+set bug_id 0
+
+# This test only works on Linux
+if { ![istarget "*-*-linux-gnu*"] } {
+    return 0
+}
+
+set testfile "attach-stopped"
+set srcfile  ${testfile}.c
+set binfile  ${objdir}/${subdir}/${testfile}
+set escapedbinfile  [string_to_regexp ${objdir}/${subdir}/${testfile}]
+
+#execute_anywhere "rm -f ${binfile}"
+remote_exec build "rm -f ${binfile}"
+# For debugging this test
+#
+#log_user 1
+
+proc corefunc { threadtype } {
+    global srcfile
+    global binfile
+    global escapedbinfile
+    global srcdir
+    global subdir
+    global gdb_prompt
+
+    if [get_compiler_info ${binfile}] {
+	return -1
+    }
+
+    # Start the program running and then wait for a bit, to be sure
+    # that it can be attached to.
+
+    set testpid [eval exec $binfile &]
+
+    # Avoid some race:
+    sleep 2
+
+    # Stop the program 
+    remote_exec build "kill -s STOP ${testpid}"
+
+    # Start with clean gdb
+    gdb_exit
+    gdb_start
+    gdb_reinitialize_dir $srcdir/$subdir
+    gdb_load ${binfile}
+
+    # Verify that we can attach to the process by first giving its
+    # executable name via the file command, and using attach with the
+    # process ID.
+
+    set test "$threadtype: set file, before attach1 to stopped process"
+    gdb_test_multiple "file $binfile" "$test" {
+       -re "Load new symbol table from.*y or n. $" {
+	    gdb_test "y" "Reading symbols from $escapedbinfile\.\.\.*done." \
+		    "$test (re-read)"
+	}
+	-re "Reading symbols from $escapedbinfile\.\.\.*done.*$gdb_prompt $" {
+	    pass "$test"
+	}
+    }
+
+    set test "$threadtype: attach1 to stopped, after setting file"
+    gdb_test_multiple "attach $testpid" "$test" {
+	-re "Attaching to program.*`?$escapedbinfile'?, process $testpid.*$gdb_prompt $" {
+	    pass "$test"
+	}
+    }
+
+    if {[string equal $threadtype threaded]} {
+	gdb_test "thread apply all bt" ".*sleep.*clone.*" "$threadtype: attach1 to stopped bt"
+    } else {
+	gdb_test "bt" ".*sleep.*main.*" "$threadtype: attach1 to stopped bt"
+    }
+
+    # Exit and detach the process.
+       
+    gdb_exit
+
+    # Avoid some race:
+    sleep 2
+
+    if [catch {open /proc/${testpid}/status r} fileid] {
+	set line2 "NOTFOUND"
+    } else {
+	gets $fileid line1;
+	gets $fileid line2;
+	close $fileid;
+    }
+
+    set test "$threadtype: attach1, exit leaves process stopped"
+    if {[string match "*(stopped)*" $line2]} {
+      pass $test
+    } else {
+      fail $test
+    }
+
+    # At this point, the process should still be stopped
+
+    gdb_start
+    gdb_reinitialize_dir $srcdir/$subdir
+    gdb_load ${binfile}
+
+    # Verify that we can attach to the process just by giving the
+    # process ID.
+       
+    set test "$threadtype: attach2 to stopped, after setting file"
+    gdb_test_multiple "attach $testpid" "$test" {
+	-re "Attaching to program.*`?$escapedbinfile'?, process $testpid.*$gdb_prompt $" {
+	    pass "$test"
+	}
+    }
+
+    if {[string equal $threadtype threaded]} {
+	gdb_test "thread apply all bt" ".*sleep.*clone.*" "$threadtype: attach2 to stopped bt"
+    } else {
+	gdb_test "bt" ".*sleep.*main.*" "$threadtype: attach2 to stopped bt"
+    }
+    gdb_breakpoint [gdb_get_line_number "$threadtype: Second sleep"]
+    set test "$threadtype: attach2 continue"
+    send_gdb "continue\n"
+    gdb_expect {
+      -re "Continuing"
+	{ pass "continue ($test)" }
+      timeout
+	{ fail "continue ($test) (timeout)" }
+    }
+
+    # For this to work we must be sure to consume the "Continuing."
+    # message first, or GDB's signal handler may not be in place.
+    after 1000 {send_gdb "\003"}
+    set test "$threadtype: attach2 stop interrupt"
+    gdb_expect 10 {
+      -re "Program received signal SIGINT.*$gdb_prompt $"
+	{
+	  pass $test
+	}
+      -re "Breakpoint \[0-9\].*$srcfile.*$gdb_prompt $"
+	{
+	  pass $test
+	}
+      timeout
+	{
+	  fail $test
+	}
+    }
+
+    gdb_exit
+
+    # Avoid some race:
+    sleep 2
+
+    # At this point, the process should be sleeping
+
+    if [catch {open /proc/${testpid}/status r} fileid2] {
+	set line2 "NOTFOUND"
+    } else {
+	gets $fileid2 line1;
+	gets $fileid2 line2;
+	close $fileid2;
+    }
+
+    set test "$threadtype: attach2, exit leaves process sleeping"
+    if {[string match "*(sleeping)*" $line2]} {
+      pass $test
+    } else {
+      fail $test
+    }
+
+    # Make sure we don't leave a process around to confuse
+    # the next test run (and prevent the compile by keeping
+    # the text file busy), in case the "set should_exit" didn't
+    # work.
+       
+    remote_exec build "kill -9 ${testpid}"
+}
+
+# build the test case first without threads
+#
+if  { [gdb_compile "${srcdir}/${subdir}/${srcfile}" "${binfile}" executable {debug}] != "" } {
+    gdb_suppress_entire_file "Testcase nonthraded compile failed, so all tests in this file will automatically fail."
+}
+
+corefunc nonthreaded
+
+# build the test case first without threads
+#
+if  { [gdb_compile_pthreads "${srcdir}/${subdir}/${srcfile}" "${binfile}" executable {debug additional_flags=-DUSE_THREADS}] != "" } {
+    gdb_suppress_entire_file "Testcase threaded compile failed, so all tests in this file will automatically fail."
+}
+
+corefunc threaded
+
+return 0
--- ./gdb/doc/gdb.texinfo	1 Jul 2007 09:13:05 -0000	1.418
+++ ./gdb/doc/gdb.texinfo	1 Jul 2007 09:55:14 -0000
@@ -2167,16 +2167,29 @@ can step and continue; you can modify st
 process continue running, you may use the @code{continue} command after
 attaching @value{GDBN} to the process.
 
+For a process already being stopped before the @code{attach} command executed
+you get the informational message below.  Other signals may be occasionally
+shown if they were being delivered right the time the @code{attach} command
+executed.  Such process is left still stopped after the @code{detach} command
+as long as you have not used the @code{continue} command (or similiar one)
+during your debugging session.
+
+@smallexample
+Attaching to program: /bin/sleep, process 16289
+Redelivering pending Stopped (signal).
+@end smallexample
+
 @table @code
 @kindex detach
 @item detach
 When you have finished debugging the attached process, you can use the
-@code{detach} command to release it from @value{GDBN} control.  Detaching
-the process continues its execution.  After the @code{detach} command,
-that process and @value{GDBN} become completely independent once more, and you
-are ready to @code{attach} another process or start one with @code{run}.
-@code{detach} does not repeat if you press @key{RET} again after
-executing the command.
+@code{detach} command to release it from @value{GDBN} control.  Detaching the
+process continues its execution unless it was already stopped before the
+attachment and a @code{continue} type command has not been executed.  After the
+@code{detach} command, that process and @value{GDBN} become completely
+independent once more, and you are ready to @code{attach} another process or
+start one with @code{run}.  @code{detach} does not repeat if you press
+@key{RET} again after executing the command.
 @end table
 
 If you exit @value{GDBN} while you have an attached process, you detach