sleep 1h& pid=$!; kill -STOP $pid; gdb sleep $pid
	->
Attaching to program: /bin/sleep, process 20768
../../gdb/linux-nat.c:1057: internal-error: linux_nat_attach: Assertion `pid == GET_PID (inferior_ptid) && WIFSTOPPED (status) && WSTOPSIG (status) == SIGSTOP' failed.

Specific to Red Hat kernels, kernel.org kernels lockup on gdb "attach".


2006-09-17  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* gdb-6.5/gdb/linux-nat.c (linux_nat_attach): Handle already stopped
	processes.

2006-09-17  Jeff Johnston  <jjohnstn@redhat.com>
	    Jan Kratochvil  <jan.kratochvil@redhat.com>

	* gdb.base/attachstop.exp, gdb.base/attachstop.c: New files,
	test attaching to already stopped processes.


Index: gdb-6.5/gdb/linux-nat.c
===================================================================
RCS file: /cvs/src/src/gdb/linux-nat.c,v
retrieving revision 1.50
diff -u -p -r1.50 linux-nat.c
--- gdb-6.5-orig/gdb/linux-nat.c	16 Sep 2006 09:48:12 -0000	1.50
+++ gdb-6.5/gdb/linux-nat.c	17 Sep 2006 21:50:32 -0000
@@ -1022,13 +1022,16 @@ linux_nat_attach (char *args, int from_t
       lp->cloned = 1;
     }
 
-  gdb_assert (pid == GET_PID (inferior_ptid)
-	      && WIFSTOPPED (status) && WSTOPSIG (status) == SIGSTOP);
+  /* Do not check `WSTOPSIG (status) == SIGSTOP' as the status may be
+     arbitrary - depending on the signal that stopped the processes.
+     If the process was running we get SIGSTOP, if it was already stopped
+     by SIGSTOP we get 0.  The value gets used for `PTRACE_CONT'.  */
+  gdb_assert (pid == GET_PID (inferior_ptid) && WIFSTOPPED (status));
 
   lp->stopped = 1;
 
-  /* Fake the SIGSTOP that core GDB expects.  */
-  lp->status = W_STOPCODE (SIGSTOP);
+  /* Provide the stop status that core GDB expects.  */
+  lp->status = status;
   lp->resumed = 1;
   if (debug_linux_nat)
     {
Index: gdb-6.5/gdb/testsuite/gdb.base/attachstop.c
===================================================================
RCS file: gdb-6.5/gdb/testsuite/gdb.base/attachstop.c
diff -N gdb-6.5/gdb/testsuite/gdb.base/attachstop.c
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ gdb-6.5/gdb/testsuite/gdb.base/attachstop.c	17 Sep 2006 21:50:32 -0000
@@ -0,0 +1,29 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2005 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 <unistd.h>
+
+int main ()
+{
+  sleep (10000);  /* Ridiculous time, but we will eventually kill it.  */
+  sleep (10000);  /* Second sleep.  */
+  return 0;
+}
Index: gdb-6.5/gdb/testsuite/gdb.base/attachstop.exp
===================================================================
RCS file: gdb-6.5/gdb/testsuite/gdb.base/attachstop.exp
diff -N gdb-6.5/gdb/testsuite/gdb.base/attachstop.exp
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ gdb-6.5/gdb/testsuite/gdb.base/attachstop.exp	17 Sep 2006 21:50:32 -0000
@@ -0,0 +1,198 @@
+# Copyright 2005-2006
+
+# 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 "attachstop"
+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 ${binfile}"
+# For debugging this test
+#
+#log_user 1
+
+# build the test case
+#
+if  { [gdb_compile "${srcdir}/${subdir}/${srcfile}" "${binfile}" executable {debug}] != "" } {
+    gdb_suppress_entire_file "Testcase compile failed, so all tests in this file will automatically fail."
+}
+
+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 &]
+exec 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 "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 "attach1 to stopped, after setting file"
+gdb_test_multiple "attach $testpid" "$test" {
+    -re "Attaching to program.*`?$escapedbinfile'?, process $testpid.*$gdb_prompt $" {
+        pass "$test"
+    }
+}
+
+gdb_test "bt" ".*sleep.*main.*" "attach1 to stopped bt"
+
+# Exit and detach the process.
+   
+gdb_exit
+
+set fileid [open /proc/${testpid}/status r];
+gets $fileid line1;
+gets $fileid line2;
+close $fileid;
+
+set test "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 "attach2 to stopped, after setting file"
+gdb_test_multiple "attach $testpid" "$test" {
+    -re "Attaching to program.*`?$escapedbinfile'?, process $testpid.*$gdb_prompt $" {
+        pass "$test"
+    }
+}
+
+gdb_test "bt" ".*sleep.*main.*" "attach2 to stopped bt"
+gdb_breakpoint [gdb_get_line_number "Second sleep"]
+set test "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 "attach2 stop unbreakable interrupt"
+gdb_expect 4 {
+  -re "Program received signal SIGINT.*$gdb_prompt $"
+    {
+      fail "$test (broke into)"
+    }
+  -re "Breakpoint \[0-9\].*$srcfile.*$gdb_prompt $"
+    {
+      fail "$test (broke into)"
+    }
+  timeout
+    {
+      pass $test
+    }
+}
+
+# Continue the program 
+remote_exec build "kill -s CONT ${testpid}"
+
+# Already sent before: after 1000 {send_gdb "\003"}
+set test "attach2 stop by interrupt"
+gdb_expect {
+  -re "Program received signal SIGINT.*$gdb_prompt $"
+    {
+      pass $test
+    }
+  -re "Breakpoint \[0-9\].*$srcfile.*$gdb_prompt $"
+    {
+      pass $test
+    }
+  timeout
+    {
+      fail "$test (timeout)"
+    }
+}
+
+gdb_exit
+
+# At this point, the process should be sleeping
+
+set fileid2 [open /proc/${testpid}/status r];
+gets $fileid2 line1;
+gets $fileid2 line2;
+close $fileid2;
+
+set test "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}"
+
+return 0