[rfc][2/2] Signal delivery + software single-step is broken

["Ulrich Weigand" <uweigand at de dot ibm dot com>]

Hello,

even with the previous patch, some sigstep.exp tests are still failing.
This is due to a peculiarity of the linux-nat target, which sometimes
decides to *not* report a signal event to GDB's main event loop, but
simply re-dispatch the inferior directly.

This is broken if GDB actually needs to handle signal delivery specially,
which is in particular the case if we're currently single-stepping.
Therefore, linux-nat refrains from such by-passing of the main event
loop if single-stepping is in progress.  However, it does so by simply
checking the "step" flag that was passed to its resume implementation.
But this flag will always be zero on targets that do software single-
stepping -- but those also must not bypass signal delivery ...

The patch below changes linux_nat_wait_1 to actually look at the stepping
status of the thread directly, instead of relying on the "step" flag.
This means the "currently_stepping" routine has to be exported from
infrun.c so it can be called here.

Thoughts?

Patch tested on arm-linux, i386-linux, s390-linux, powerpc-linux.

Bye,
Ulrich



ChangeLog:

	* linux-nat.c (linux_nat_wait_1): Do not short-cut signal delivery
	while software single-step in progress.
	* inferior.h (struct thread_info): Add forward declaration.
	(currently_stepping): Add prototype.
	* infrun.c (currently_stepping): Remove prototype.  Make global.

Index: gdb/inferior.h
===================================================================
RCS file: /cvs/src/src/gdb/inferior.h,v
retrieving revision 1.149
diff -u -p -r1.149 inferior.h
--- gdb/inferior.h	9 Jan 2011 03:08:56 -0000	1.149
+++ gdb/inferior.h	17 Jan 2011 19:15:00 -0000
@@ -31,6 +31,7 @@ struct gdbarch;
 struct regcache;
 struct ui_out;
 struct terminal_info;
+struct thread_info;
 
 /* For bpstat.  */
 #include "breakpoint.h"
@@ -253,6 +254,8 @@ extern void ensure_not_running (void);
 
 void set_step_info (struct frame_info *frame, struct symtab_and_line sal);
 
+extern int currently_stepping (struct thread_info *tp);
+
 /* From infcmd.c */
 
 extern void post_create_inferior (struct target_ops *, int);
Index: gdb/infrun.c
===================================================================
RCS file: /cvs/src/src/gdb/infrun.c,v
retrieving revision 1.467
diff -u -p -r1.467 infrun.c
--- gdb/infrun.c	9 Jan 2011 03:08:56 -0000	1.467
+++ gdb/infrun.c	17 Jan 2011 19:15:05 -0000
@@ -76,8 +76,6 @@ static int follow_fork (void);
 static void set_schedlock_func (char *args, int from_tty,
 				struct cmd_list_element *c);
 
-static int currently_stepping (struct thread_info *tp);
-
 static int currently_stepping_or_nexting_callback (struct thread_info *tp,
 						   void *data);
 
@@ -4957,7 +4979,7 @@ process_event_stop_test:
 
 /* Is thread TP in the middle of single-stepping?  */
 
-static int
+int
 currently_stepping (struct thread_info *tp)
 {
   return ((tp->control.step_range_end
Index: gdb/linux-nat.c
===================================================================
RCS file: /cvs/src/src/gdb/linux-nat.c,v
retrieving revision 1.191
diff -u -p -r1.191 linux-nat.c
--- gdb/linux-nat.c	9 Jan 2011 03:08:57 -0000	1.191
+++ gdb/linux-nat.c	17 Jan 2011 19:15:08 -0000
@@ -3604,7 +3604,7 @@ retry:
 	 single-stepping, since that may need special care, e.g. to
 	 skip the signal handler, or, if we're gaining control of the
 	 inferior.  */
-      if (!lp->step
+      if (!currently_stepping (find_thread_ptid (lp->ptid))
 	  && inf->control.stop_soon == NO_STOP_QUIETLY
 	  && signal_stop_state (signo) == 0
 	  && signal_print_state (signo) == 0
-- 
  Dr. Ulrich Weigand
  GNU Toolchain for Linux on System z and Cell BE
  Ulrich.Weigand@de.ibm.com