gdb-python-gil.patch

;; Fix Python GIL with gdb.execute("continue") (Phil Muldoon, BZ 1116957).
;;=push

Author: ivanivanov884

gdb/doc/python.texi

@@ -234,6 +234,14 @@ returned as a string.  The default is @code{False}, in which case the
 return value is @code{None}.  If @var{to_string} is @code{True}, the
 @value{GDBN} virtual terminal will be temporarily set to unlimited width
 and height, and its pagination will be disabled; @pxref{Screen Size}.
+
+The @var{release_gil} flag specifies whether @value{GDBN} ought to
+release the Python GIL before executing the command.  This is useful
+in multi-threaded Python programs where by default the Python
+interpreter will acquire the GIL and lock other threads from
+executing.  After the command has completed executing in @value{GDBN}
+the Python GIL is reacquired. This flag must be a boolean value.  If
+omitted, it defaults to @code{False}.
 @end defun
 
 @findex gdb.breakpoints

gdb/python/python-internal.h

@@ -115,6 +115,8 @@
 #define PyGILState_Release(ARG) ((void)(ARG))
 #define PyEval_InitThreads()
 #define PyThreadState_Swap(ARG) ((void)(ARG))
+#define PyEval_SaveThread() ((void)(ARG))
+#define PyEval_RestoreThread(ARG) ((void)(ARG))
 #define PyEval_ReleaseLock()
 #endif
 

gdb/python/python.c

@@ -543,12 +543,16 @@ execute_gdb_command (PyObject *self, PyObject *args, PyObject *kw)
 {
   const char *arg;
   PyObject *from_tty_obj = NULL, *to_string_obj = NULL;
-  int from_tty, to_string;
-  static const char *keywords[] = { "command", "from_tty", "to_string", NULL };
+  int from_tty, to_string, release_gil;
+  static const char *keywords[] = {"command", "from_tty", "to_string", "release_gil", NULL };
+  PyObject *release_gil_obj = NULL;
+  /* Initialize it just to avoid a GCC false warning.  */
+  PyThreadState *state = NULL;
 
-  if (!gdb_PyArg_ParseTupleAndKeywords (args, kw, "s|O!O!", keywords, &arg,
+  if (!gdb_PyArg_ParseTupleAndKeywords (args, kw, "s|O!O!O!", keywords, &arg,
 					&PyBool_Type, &from_tty_obj,
-					&PyBool_Type, &to_string_obj))
+					&PyBool_Type, &to_string_obj,
+					&PyBool_Type, &release_gil_obj))
     return NULL;
 
   from_tty = 0;
@@ -569,6 +573,15 @@ execute_gdb_command (PyObject *self, PyObject *args, PyObject *kw)
       to_string = cmp;
     }
 
+  release_gil = 0;
+  if (release_gil_obj)
+    {
+      int cmp = PyObject_IsTrue (release_gil_obj);
+      if (cmp < 0)
+	return NULL;
+      release_gil = cmp;
+    }
+
   std::string to_string_res;
 
   scoped_restore preventer = prevent_dont_repeat ();
@@ -593,10 +606,16 @@ execute_gdb_command (PyObject *self, PyObject *args, PyObject *kw)
 
       counted_command_line lines = read_command_lines_1 (reader, 1, nullptr);
 
+      /* In the case of long running GDB commands, allow the user to
+	 release the Python GIL acquired by Python.  Restore the GIL
+	 after the command has completed before handing back to
+	 Python.  */
+      if (release_gil)
+	state = PyEval_SaveThread();
+
       {
 	scoped_restore save_async = make_scoped_restore (&current_ui->async,
 							 0);
-
 	scoped_restore save_uiout = make_scoped_restore (&current_uiout);
 
 	/* Use the console interpreter uiout to have the same print format
@@ -611,12 +630,24 @@ execute_gdb_command (PyObject *self, PyObject *args, PyObject *kw)
 	  execute_control_commands (lines.get (), from_tty);
       }
 
+      /* Reacquire the GIL if it was released earlier.  */
+      if (release_gil)
+	PyEval_RestoreThread (state);
+
       /* Do any commands attached to breakpoint we stopped at.  */
       bpstat_do_actions ();
     }
   catch (const gdb_exception &except)
     {
-      GDB_PY_HANDLE_EXCEPTION (except);
+      if (except.reason < 0)
+	{
+	  /* Reacquire the GIL if it was released earlier.  */
+	  if (release_gil)
+	    PyEval_RestoreThread (state);
+
+	  gdbpy_convert_exception (except);
+	  return NULL;
+	}
     }
 
   if (to_string)

gdb/testsuite/gdb.python/py-gil-mthread.c

@@ -0,0 +1,13 @@
+#include <stdio.h>
+#include <unistd.h>
+
+int
+main (void)
+{
+  int i;
+  for (i = 0; i < 10; i++)
+    {
+      sleep (1); /* break-here */
+      printf ("Sleeping %d\n", i);
+    }
+}

gdb/testsuite/gdb.python/py-gil-mthread.exp

@@ -0,0 +1,69 @@
+# Copyright (C) 2014 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 3 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, see <http://www.gnu.org/licenses/>.
+
+standard_testfile .c .py
+set executable $testfile
+
+if { [prepare_for_testing $testfile.exp $executable $srcfile] } {
+    return -1
+}
+
+# Skip all tests if Python scripting is not enabled.
+if { [skip_python_tests] } { continue }
+
+if ![runto_main] {
+    return -1
+}
+
+gdb_breakpoint $srcfile:[gdb_get_line_number "break-here"] temporary
+gdb_continue_to_breakpoint "break-here" ".* break-here .*"
+
+set test "response"
+set timeout 60
+set sleeping_last -1
+set hello_last 0
+set minimal 5
+gdb_test_multiple "python exec (open ('$srcdir/$subdir/$srcfile2').read ())" $test {
+    -re "Error: unable to start thread\r\n" {
+	fail $test
+	# Not $gdb_prompt-synced!
+    }
+    -re "Sleeping (\[0-9\]+)\r\n" {
+	set n $expect_out(1,string)
+	if { $sleeping_last + 1 != $n } {
+	    fail $test
+	} else {
+	    set sleeping_last $n
+	    if { $sleeping_last >= $minimal && $hello_last >= $minimal } {
+		pass $test
+	    } else {
+		exp_continue
+	    }
+	}
+    }
+    -re "Hello \\( (\[0-9\]+) \\)\r\n" {
+	set n $expect_out(1,string)
+	if { $hello_last + 1 != $n } {
+	    fail $test
+	} else {
+	    set hello_last $n
+	    if { $sleeping_last >= $minimal && $hello_last >= $minimal } {
+		pass $test
+	    } else {
+		exp_continue
+	    }
+	}
+    }
+}

gdb/testsuite/gdb.python/py-gil-mthread.py

@@ -0,0 +1,28 @@
+try:
+   import thread
+except:
+   import _thread
+import time
+import gdb
+
+# Define a function for the thread
+def print_thread_hello():
+   count = 0
+   while count < 10:
+      time.sleep(1)
+      count += 1
+      print ("Hello ( %d )" % count)
+
+# Create a threads a continue
+try:
+   thread.start_new_thread (print_thread_hello, ())
+   gdb.execute ("continue", release_gil=True)
+except:
+   try:
+      _thread.start_new_thread (print_thread_hello, ())
+      gdb.execute ("continue", release_gil=True)
+   except:
+      print ("Error: unable to start thread")
+
+while 1:
+   pass