Always pass signals to the right thread

Currently, GDB can pass a signal to the wrong thread in several
different but related scenarios.

E.g., if thread 1 stops for signal SIGFOO, the user switches to thread
2, and then issues "continue", SIGFOO is actually delivered to thread
2, not thread 1.  This obviously messes up programs that use
pthread_kill to send signals to specific threads.

This has been a known issue for a long while.  Back in 2008 when I
made stop_signal be per-thread (2020b7ab), I kept the behavior -- see
code in 'proceed' being removed -- wanting to come back to it later.
The time has finally come now.

The patch fixes this -- on resumption, intercepted signals are always
delivered to the thread that had intercepted them.

Another example: if thread 1 stops for a breakpoint, the user switches
to thread 2, and then issues "signal SIGFOO", SIGFOO is actually
delivered to thread 1, not thread 2, because 'proceed' first switches
to thread 1 to step over its breakpoint...  If the user deletes the
breakpoint before issuing "signal FOO", then the signal is delivered
to thread 2 (the current thread).

"signal SIGFOO" can be used for two things: inject a signal in the
program while the program/thread had stopped for none, bypassing
"handle nopass"; or changing/suppressing a signal the program had
stopped for.  These scenarios are really two faces of the same coin,
and GDB can't really guess what the user is trying to do.  GDB might
have intercepted signals in more than one thread even (see the new
signal-command-multiple-signals-pending.exp test).  At least in the
inject case, it's obviously clear to me that the user means to deliver
the signal to the currently selected thread, so best is to make the
command's behavior consistent and easy to explain.

Then, if the user is trying to suppress/change a signal the program
had stopped for instead of injecting a new signal, but, the user had
changed threads meanwhile, then she will be surprised that with:

  (gdb) continue
  Thread 1 stopped for signal SIGFOO.
  (gdb) thread 2
  (gdb) signal SIGBAR

... GDB actually delivers SIGFOO to thread 1, and SIGBAR to thread 2
(with scheduler-locking off, which is the default, because then
"signal" or any other resumption command resumes all threads).

So the patch makes GDB detect that, and ask for confirmation:

  (gdb) thread 1
  [Switching to thread 1 (Thread 10979)]
  (gdb) signal SIGUSR2
  Note:
    Thread 3 previously stopped with signal SIGUSR2, User defined signal 2.
    Thread 2 previously stopped with signal SIGUSR1, User defined signal 1.
  Continuing thread 1 (the current thread) with specified signal will
  still deliver the signals noted above to their respective threads.
  Continue anyway? (y or n)

All these scenarios are covered by the new tests.

Tested on x86_64 Fedora 20, native and gdbserver.

gdb/
2014-07-25  Pedro Alves  <palves@redhat.com>

	* NEWS: Mention signal passing and "signal" command changes.
	* gdbthread.h (struct thread_suspend_state) <stop_signal>: Extend
	comment.
	* breakpoint.c (until_break_command): Adjust clear_proceed_status
	call.
	* infcall.c (run_inferior_call): Adjust clear_proceed_status call.
	* infcmd.c (proceed_thread_callback, continue_1, step_once)
	(jump_command): Adjust clear_proceed_status call.
	(signal_command): Warn if other thread that are resumed have
	signals that will be delivered.  Adjust clear_proceed_status call.
	(until_next_command, finish_command)
	(proceed_after_attach_callback, attach_command_post_wait)
	(attach_command): Adjust clear_proceed_status call.
	* infrun.c (proceed_after_vfork_done): Likewise.
	(proceed_after_attach_callback): Adjust comment.
	(clear_proceed_status_thread): Clear stop_signal if not in pass
	state.
	(clear_proceed_status_callback): Delete.
	(clear_proceed_status): New 'step' parameter.  Only clear the
	proceed status of threads the command being prepared is about to
	resume.
	(proceed): If passed in an explicit signal, override stop_signal
	with it.  Don't pass the last stop signal to the thread we're
	resuming.
	(init_wait_for_inferior): Adjust clear_proceed_status call.
	(switch_back_to_stepped_thread): Clear the signal if it should not
	be passed.
	* infrun.h (clear_proceed_status): New 'step' parameter.
	(user_visible_resume_ptid): Add comment.
	* linux-nat.c (linux_nat_resume_callback): Don't check whether the
	signal is in pass state.
	* remote.c (append_pending_thread_resumptions): Likewise.
	* mi/mi-main.c (proceed_thread): Adjust clear_proceed_status call.

gdb/doc/
2014-07-25  Pedro Alves  <palves@redhat.com>
	    Eli Zaretskii  <eliz@gnu.org>

	* gdb.texinfo (Signaling) <signal command>: Explain what happens
	with multi-threaded programs.

gdb/testsuite/
2014-07-25  Pedro Alves  <palves@redhat.com>

	* gdb.threads/signal-command-handle-nopass.c: New file.
	* gdb.threads/signal-command-handle-nopass.exp: New file.
	* gdb.threads/signal-command-multiple-signals-pending.c: New file.
	* gdb.threads/signal-command-multiple-signals-pending.exp: New file.
	* gdb.threads/signal-delivered-right-thread.c: New file.
	* gdb.threads/signal-delivered-right-thread.exp: New file.

20 files changed, 716 insertions, 79 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 11cdbf8..dd41478 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,39 @@
+2014-07-25  Pedro Alves  <palves@redhat.com>
+
+	* NEWS: Mention signal passing and "signal" command changes.
+	* gdbthread.h (struct thread_suspend_state) <stop_signal>: Extend
+	comment.
+	* breakpoint.c (until_break_command): Adjust clear_proceed_status
+	call.
+	* infcall.c (run_inferior_call): Adjust clear_proceed_status call.
+	* infcmd.c (proceed_thread_callback, continue_1, step_once)
+	(jump_command): Adjust clear_proceed_status call.
+	(signal_command): Warn if other thread that are resumed have
+	signals that will be delivered.  Adjust clear_proceed_status call.
+	(until_next_command, finish_command)
+	(proceed_after_attach_callback, attach_command_post_wait)
+	(attach_command): Adjust clear_proceed_status call.
+	* infrun.c (proceed_after_vfork_done): Likewise.
+	(proceed_after_attach_callback): Adjust comment.
+	(clear_proceed_status_thread): Clear stop_signal if not in pass
+	state.
+	(clear_proceed_status_callback): Delete.
+	(clear_proceed_status): New 'step' parameter.  Only clear the
+	proceed status of threads the command being prepared is about to
+	resume.
+	(proceed): If passed in an explicit signal, override stop_signal
+	with it.  Don't pass the last stop signal to the thread we're
+	resuming.
+	(init_wait_for_inferior): Adjust clear_proceed_status call.
+	(switch_back_to_stepped_thread): Clear the signal if it should not
+	be passed.
+	* infrun.h (clear_proceed_status): New 'step' parameter.
+	(user_visible_resume_ptid): Add comment.
+	* linux-nat.c (linux_nat_resume_callback): Don't check whether the
+	signal is in pass state.
+	* remote.c (append_pending_thread_resumptions): Likewise.
+	* mi/mi-main.c (proceed_thread): Adjust clear_proceed_status call.
+
 2014-07-25  Tom Tromey  <tromey@redhat.com>
 
 	* target.h (target_stopped_data_address)
diff --git a/gdb/NEWS b/gdb/NEWS
index d9a19ae..2b61ff4 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -3,6 +3,17 @@
 
 *** Changes since GDB 7.8
 
+* On resume, GDB now always passes the signal the program had stopped
+  for to the thread the signal was sent to, even if the user changed
+  threads before resuming.  Previously GDB would often (but not
+  always) deliver the signal to the thread that happens to be current
+  at resume time.
+
+* Conversely, the "signal" command now consistently delivers the
+  requested signal to the current thread.  GDB now asks for
+  confirmation if the program had stopped for a signal and the user
+  switched threads meanwhile.
+
 *** Changes in GDB 7.8
 
 * New command line options
diff --git a/gdb/breakpoint.c b/gdb/breakpoint.c
index 1c6070f..262e992 100644
--- a/gdb/breakpoint.c
+++ b/gdb/breakpoint.c
@@ -11668,7 +11668,7 @@ until_break_command (char *arg, int from_tty, int anywhere)
   int thread;
   struct thread_info *tp;
 
-  clear_proceed_status ();
+  clear_proceed_status (0);
 
   /* Set a breakpoint where the user wants it and at return from
      this function.  */
diff --git a/gdb/doc/ChangeLog b/gdb/doc/ChangeLog
index 67998ca..41de328 100644
--- a/gdb/doc/ChangeLog
+++ b/gdb/doc/ChangeLog
@@ -1,3 +1,9 @@
+2014-07-25  Pedro Alves  <palves@redhat.com>
+	    Eli Zaretskii  <eliz@gnu.org>
+
+	* gdb.texinfo (Signaling) <signal command>: Explain what happens
+	with multi-threaded programs.
+
 2014-06-27  Yao Qi  <yao@codesourcery.com>
 
 	* gdb.texinfo (Maintenance Commands): Update the output of
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 8101b87..32f709a 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -16546,7 +16546,7 @@ detail.
 @table @code
 @kindex signal
 @item signal @var{signal}
-Resume execution where your program stopped, but immediately give it the
+Resume execution where your program is stopped, but immediately give it the
 signal @var{signal}.  The @var{signal} can be the name or the number of a
 signal.  For example, on many systems @code{signal 2} and @code{signal
 SIGINT} are both ways of sending an interrupt signal.
@@ -16557,6 +16557,15 @@ a signal and would ordinarily see the signal when resumed with the
 @code{continue} command; @samp{signal 0} causes it to resume without a
 signal.
 
+@emph{Note:} When resuming a multi-threaded program, @var{signal} is
+delivered to the currently selected thread, not the thread that last
+reported a stop.  This includes the situation where a thread was
+stopped due to a signal.  So if you want to continue execution
+suppressing the signal that stopped a thread, you should select that
+same thread before issuing the @samp{signal 0} command.  If you issue
+the @samp{signal 0} command with another thread as the selected one,
+@value{GDBN} detects that and asks for confirmation.
+
 @code{signal} does not repeat when you press @key{RET} a second time
 after executing the command.
 @end table
diff --git a/gdb/gdbthread.h b/gdb/gdbthread.h
index 9ef74cd..522b674 100644
--- a/gdb/gdbthread.h
+++ b/gdb/gdbthread.h
@@ -135,7 +135,13 @@ struct thread_control_state
 
 struct thread_suspend_state
 {
-  /* Last signal that the inferior received (why it stopped).  */
+  /* Last signal that the inferior received (why it stopped).  When
+     the thread is resumed, this signal is delivered.  Note: the
+     target should not check whether the signal is in pass state,
+     because the signal may have been explicitly passed with the
+     "signal" command, which overrides "handle nopass".  If the signal
+     should be suppressed, the core will take care of clearing this
+     before the target is resumed.  */
   enum gdb_signal stop_signal;
 };
 
diff --git a/gdb/infcall.c b/gdb/infcall.c
index a9b1ceb..5c65bb5 100644
--- a/gdb/infcall.c
+++ b/gdb/infcall.c
@@ -396,7 +396,7 @@ run_inferior_call (struct thread_info *call_thread, CORE_ADDR real_pc)
 
   call_thread->control.in_infcall = 1;
 
-  clear_proceed_status ();
+  clear_proceed_status (0);
 
   disable_watchpoints_before_interactive_call_start ();
 
diff --git a/gdb/infcmd.c b/gdb/infcmd.c
index 021a587..5eb092b8 100644
--- a/gdb/infcmd.c
+++ b/gdb/infcmd.c
@@ -679,7 +679,7 @@ proceed_thread_callback (struct thread_info *thread, void *arg)
     return 0;
 
   switch_to_thread (thread->ptid);
-  clear_proceed_status ();
+  clear_proceed_status (0);
   proceed ((CORE_ADDR) -1, GDB_SIGNAL_DEFAULT, 0);
   return 0;
 }
@@ -745,7 +745,7 @@ continue_1 (int all_threads)
     {
       ensure_valid_thread ();
       ensure_not_running ();
-      clear_proceed_status ();
+      clear_proceed_status (0);
       proceed ((CORE_ADDR) -1, GDB_SIGNAL_DEFAULT, 0);
     }
 }
@@ -1013,7 +1013,7 @@ step_once (int skip_subroutines, int single_inst, int count, int thread)
 	 THREAD is set.  */
       struct thread_info *tp = inferior_thread ();
 
-      clear_proceed_status ();
+      clear_proceed_status (!skip_subroutines);
       set_step_frame ();
 
       if (!single_inst)
@@ -1186,7 +1186,7 @@ jump_command (char *arg, int from_tty)
       printf_filtered (".\n");
     }
 
-  clear_proceed_status ();
+  clear_proceed_status (0);
   proceed (addr, GDB_SIGNAL_0, 0);
 }
 
@@ -1245,6 +1245,50 @@ signal_command (char *signum_exp, int from_tty)
 	oursig = gdb_signal_from_command (num);
     }
 
+  /* Look for threads other than the current that this command ends up
+     resuming too (due to schedlock off), and warn if they'll get a
+     signal delivered.  "signal 0" is used to suppress a previous
+     signal, but if the current thread is no longer the one that got
+     the signal, then the user is potentially suppressing the signal
+     of the wrong thread.  */
+  if (!non_stop)
+    {
+      struct thread_info *tp;
+      ptid_t resume_ptid;
+      int must_confirm = 0;
+
+      /* This indicates what will be resumed.  Either a single thread,
+	 a whole process, or all threads of all processes.  */
+      resume_ptid = user_visible_resume_ptid (0);
+
+      ALL_NON_EXITED_THREADS (tp)
+	{
+	  if (ptid_equal (tp->ptid, inferior_ptid))
+	    continue;
+	  if (!ptid_match (tp->ptid, resume_ptid))
+	    continue;
+
+	  if (tp->suspend.stop_signal != GDB_SIGNAL_0
+	      && signal_pass_state (tp->suspend.stop_signal))
+	    {
+	      if (!must_confirm)
+		printf_unfiltered (_("Note:\n"));
+	      printf_unfiltered (_("  Thread %d previously stopped with signal %s, %s.\n"),
+				 tp->num,
+				 gdb_signal_to_name (tp->suspend.stop_signal),
+				 gdb_signal_to_string (tp->suspend.stop_signal));
+	      must_confirm = 1;
+	    }
+	}
+
+      if (must_confirm
+	  && !query (_("Continuing thread %d (the current thread) with specified signal will\n"
+		       "still deliver the signals noted above to their respective threads.\n"
+		       "Continue anyway? "),
+		     inferior_thread ()->num))
+	error (_("Not confirmed."));
+    }
+
   if (from_tty)
     {
       if (oursig == GDB_SIGNAL_0)
@@ -1254,7 +1298,7 @@ signal_command (char *signum_exp, int from_tty)
 			 gdb_signal_to_name (oursig));
     }
 
-  clear_proceed_status ();
+  clear_proceed_status (0);
   proceed ((CORE_ADDR) -1, oursig, 0);
 }
 
@@ -1295,7 +1339,7 @@ until_next_command (int from_tty)
   int thread = tp->num;
   struct cleanup *old_chain;
 
-  clear_proceed_status ();
+  clear_proceed_status (0);
   set_step_frame ();
 
   frame = get_current_frame ();
@@ -1686,7 +1730,7 @@ finish_command (char *arg, int from_tty)
   if (frame == 0)
     error (_("\"finish\" not meaningful in the outermost frame."));
 
-  clear_proceed_status ();
+  clear_proceed_status (0);
 
   /* Finishing from an inline frame is completely different.  We don't
      try to show the "return value" - no way to locate it.  So we do
@@ -2298,7 +2342,7 @@ proceed_after_attach_callback (struct thread_info *thread,
       && thread->suspend.stop_signal == GDB_SIGNAL_0)
     {
       switch_to_thread (thread->ptid);
-      clear_proceed_status ();
+      clear_proceed_status (0);
       proceed ((CORE_ADDR) -1, GDB_SIGNAL_DEFAULT, 0);
     }
 
@@ -2395,7 +2439,7 @@ attach_command_post_wait (char *args, int from_tty, int async_exec)
 	{
 	  if (inferior_thread ()->suspend.stop_signal == GDB_SIGNAL_0)
 	    {
-	      clear_proceed_status ();
+	      clear_proceed_status (0);
 	      proceed ((CORE_ADDR) -1, GDB_SIGNAL_DEFAULT, 0);
 	    }
 	}
@@ -2514,7 +2558,7 @@ attach_command (char *args, int from_tty)
   /* Set up execution context to know that we should return from
      wait_for_inferior as soon as the target reports a stop.  */
   init_wait_for_inferior ();
-  clear_proceed_status ();
+  clear_proceed_status (0);
 
   if (non_stop)
     {
diff --git a/gdb/infrun.c b/gdb/infrun.c
index 3c58ff2..33aa674 100644
--- a/gdb/infrun.c
+++ b/gdb/infrun.c
@@ -623,7 +623,7 @@ proceed_after_vfork_done (struct thread_info *thread,
 			    target_pid_to_str (thread->ptid));
 
       switch_to_thread (thread->ptid);
-      clear_proceed_status ();
+      clear_proceed_status (0);
       proceed ((CORE_ADDR) -1, GDB_SIGNAL_DEFAULT, 0);
     }
 
@@ -1721,15 +1721,6 @@ maybe_software_singlestep (struct gdbarch *gdbarch, CORE_ADDR pc)
   return hw_step;
 }
 
-/* Return a ptid representing the set of threads that we will proceed,
-   in the perspective of the user/frontend.  We may actually resume
-   fewer threads at first, e.g., if a thread is stopped at a
-   breakpoint that needs stepping-off, but that should not be visible
-   to the user/frontend, and neither should the frontend/user be
-   allowed to proceed any of the threads that happen to be stopped for
-   internal run control handling, if a previous command wanted them
-   resumed.  */
-
 ptid_t
 user_visible_resume_ptid (int step)
 {
@@ -1757,6 +1748,12 @@ user_visible_resume_ptid (int step)
       resume_ptid = inferior_ptid;
     }
 
+  /* We may actually resume fewer threads at first, e.g., if a thread
+     is stopped at a breakpoint that needs stepping-off, but that
+     should not be visible to the user/frontend, and neither should
+     the frontend/user be allowed to proceed any of the threads that
+     happen to be stopped for internal run control handling, if a
+     previous command wanted them resumed.  */
   return resume_ptid;
 }
 
@@ -2032,6 +2029,11 @@ clear_proceed_status_thread (struct thread_info *tp)
 			"infrun: clear_proceed_status_thread (%s)\n",
 			target_pid_to_str (tp->ptid));
 
+  /* If this signal should not be seen by program, give it zero.
+     Used for debugging signals.  */
+  if (!signal_pass_state (tp->suspend.stop_signal))
+    tp->suspend.stop_signal = GDB_SIGNAL_0;
+
   tp->control.trap_expected = 0;
   tp->control.step_range_start = 0;
   tp->control.step_range_end = 0;
@@ -2051,26 +2053,24 @@ clear_proceed_status_thread (struct thread_info *tp)
   bpstat_clear (&tp->control.stop_bpstat);
 }
 
-static int
-clear_proceed_status_callback (struct thread_info *tp, void *data)
-{
-  if (is_exited (tp->ptid))
-    return 0;
-
-  clear_proceed_status_thread (tp);
-  return 0;
-}
-
 void
-clear_proceed_status (void)
+clear_proceed_status (int step)
 {
   if (!non_stop)
     {
-      /* In all-stop mode, delete the per-thread status of all
-	 threads, even if inferior_ptid is null_ptid, there may be
-	 threads on the list.  E.g., we may be launching a new
-	 process, while selecting the executable.  */
-      iterate_over_threads (clear_proceed_status_callback, NULL);
+      struct thread_info *tp;
+      ptid_t resume_ptid;
+
+      resume_ptid = user_visible_resume_ptid (step);
+
+      /* In all-stop mode, delete the per-thread status of all threads
+	 we're about to resume, implicitly and explicitly.  */
+      ALL_NON_EXITED_THREADS (tp)
+        {
+	  if (!ptid_match (tp->ptid, resume_ptid))
+	    continue;
+	  clear_proceed_status_thread (tp);
+	}
     }
 
   if (!ptid_equal (inferior_ptid, null_ptid))
@@ -2252,6 +2252,9 @@ proceed (CORE_ADDR addr, enum gdb_signal siggnal, int step)
       regcache_write_pc (regcache, addr);
     }
 
+  if (siggnal != GDB_SIGNAL_DEFAULT)
+    tp->suspend.stop_signal = siggnal;
+
   /* Record the interpreter that issued the execution command that
      caused this thread to resume.  If the top level interpreter is
      MI/async, and the execution command was a CLI command
@@ -2318,38 +2321,6 @@ proceed (CORE_ADDR addr, enum gdb_signal siggnal, int step)
 
   tp->control.trap_expected = tp->stepping_over_breakpoint;
 
-  if (!non_stop)
-    {
-      /* Pass the last stop signal to the thread we're resuming,
-	 irrespective of whether the current thread is the thread that
-	 got the last event or not.  This was historically GDB's
-	 behaviour before keeping a stop_signal per thread.  */
-
-      struct thread_info *last_thread;
-      ptid_t last_ptid;
-      struct target_waitstatus last_status;
-
-      get_last_target_status (&last_ptid, &last_status);
-      if (!ptid_equal (inferior_ptid, last_ptid)
-	  && !ptid_equal (last_ptid, null_ptid)
-	  && !ptid_equal (last_ptid, minus_one_ptid))
-	{
-	  last_thread = find_thread_ptid (last_ptid);
-	  if (last_thread)
-	    {
-	      tp->suspend.stop_signal = last_thread->suspend.stop_signal;
-	      last_thread->suspend.stop_signal = GDB_SIGNAL_0;
-	    }
-	}
-    }
-
-  if (siggnal != GDB_SIGNAL_DEFAULT)
-    tp->suspend.stop_signal = siggnal;
-  /* If this signal should not be seen by program,
-     give it zero.  Used for debugging signals.  */
-  else if (!signal_program[tp->suspend.stop_signal])
-    tp->suspend.stop_signal = GDB_SIGNAL_0;
-
   annotate_starting ();
 
   /* Make sure that output from GDB appears before output from the
@@ -2443,7 +2414,7 @@ init_wait_for_inferior (void)
 
   breakpoint_init_inferior (inf_starting);
 
-  clear_proceed_status ();
+  clear_proceed_status (0);
 
   target_last_wait_ptid = minus_one_ptid;
 
@@ -5190,6 +5161,10 @@ switch_back_to_stepped_thread (struct execution_control_state *ecs)
 	 what keep_going does as well, if we call it.  */
       ecs->event_thread->control.trap_expected = 0;
 
+      /* Likewise, clear the signal if it should not be passed.  */
+      if (!signal_program[ecs->event_thread->suspend.stop_signal])
+	ecs->event_thread->suspend.stop_signal = GDB_SIGNAL_0;
+
       /* If scheduler locking applies even if not stepping, there's no
 	 need to walk over threads.  Above we've checked whether the
 	 current thread is stepping.  If some other thread not the
diff --git a/gdb/infrun.h b/gdb/infrun.h
index 66612a8..35b2246 100644
--- a/gdb/infrun.h
+++ b/gdb/infrun.h
@@ -83,7 +83,11 @@ extern struct regcache *stop_registers;
 
 extern void start_remote (int from_tty);
 
-extern void clear_proceed_status (void);
+/* Clear out all variables saying what to do when inferior is
+   continued or stepped.  First do this, then set the ones you want,
+   then call `proceed'.  STEP indicates whether we're preparing for a
+   step/stepi command.  */
+extern void clear_proceed_status (int step);
 
 extern void proceed (CORE_ADDR, enum gdb_signal, int);
 
@@ -91,6 +95,8 @@ extern void proceed (CORE_ADDR, enum gdb_signal, int);
    Normally, use `proceed', which handles a lot of bookkeeping.  */
 extern void resume (int, enum gdb_signal);
 
+/* Return a ptid representing the set of threads that we will proceed,
+   in the perspective of the user/frontend.  */
 extern ptid_t user_visible_resume_ptid (int step);
 
 extern void wait_for_inferior (void);
diff --git a/gdb/linux-nat.c b/gdb/linux-nat.c
index 7db1b3d..8d4251f 100644
--- a/gdb/linux-nat.c
+++ b/gdb/linux-nat.c
@@ -1694,8 +1694,7 @@ linux_nat_resume_callback (struct lwp_info *lp, void *except)
       thread = find_thread_ptid (lp->ptid);
       if (thread != NULL)
 	{
-	  if (signal_pass_state (thread->suspend.stop_signal))
-	    signo = thread->suspend.stop_signal;
+	  signo = thread->suspend.stop_signal;
 	  thread->suspend.stop_signal = GDB_SIGNAL_0;
 	}
     }
diff --git a/gdb/mi/mi-main.c b/gdb/mi/mi-main.c
index 96dfc71..26389f1 100644
--- a/gdb/mi/mi-main.c
+++ b/gdb/mi/mi-main.c
@@ -253,7 +253,7 @@ proceed_thread (struct thread_info *thread, int pid)
     return;
 
   switch_to_thread (thread->ptid);
-  clear_proceed_status ();
+  clear_proceed_status (0);
   proceed ((CORE_ADDR) -1, GDB_SIGNAL_DEFAULT, 0);
 }
 
diff --git a/gdb/remote.c b/gdb/remote.c
index 972c0ff..3a05bfd 100644
--- a/gdb/remote.c
+++ b/gdb/remote.c
@@ -4643,8 +4643,7 @@ append_pending_thread_resumptions (char *p, char *endp, ptid_t ptid)
   ALL_NON_EXITED_THREADS (thread)
     if (ptid_match (thread->ptid, ptid)
 	&& !ptid_equal (inferior_ptid, thread->ptid)
-	&& thread->suspend.stop_signal != GDB_SIGNAL_0
-	&& signal_pass_state (thread->suspend.stop_signal))
+	&& thread->suspend.stop_signal != GDB_SIGNAL_0)
       {
 	p = append_resumption (p, endp, thread->ptid,
 			       0, thread->suspend.stop_signal);
diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index bd8cf44..e088b9b 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,5 +1,14 @@
 2014-07-25  Pedro Alves  <palves@redhat.com>
 
+	* gdb.threads/signal-command-handle-nopass.c: New file.
+	* gdb.threads/signal-command-handle-nopass.exp: New file.
+	* gdb.threads/signal-command-multiple-signals-pending.c: New file.
+	* gdb.threads/signal-command-multiple-signals-pending.exp: New file.
+	* gdb.threads/signal-delivered-right-thread.c: New file.
+	* gdb.threads/signal-delivered-right-thread.exp: New file.
+
+2014-07-25  Pedro Alves  <palves@redhat.com>
+
 	* gdb.base/double-prompt-target-event-error.exp
 	(cancel_pagination_in_target_event): Remove '-notransfer <return>'
 	match.
diff --git a/gdb/testsuite/gdb.threads/signal-command-handle-nopass.c b/gdb/testsuite/gdb.threads/signal-command-handle-nopass.c
new file mode 100644
index 0000000..abca2f9
--- /dev/null
+++ b/gdb/testsuite/gdb.threads/signal-command-handle-nopass.c
@@ -0,0 +1,49 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 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/>.  */
+
+#include <stdio.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <pthread.h>
+#include <signal.h>
+
+void
+handler (int sig)
+{
+}
+
+void *
+thread_function (void *arg)
+{
+  volatile unsigned int i = 1;
+
+  while (i != 0)
+    usleep (1);
+}
+
+int
+main (void)
+{
+  pthread_t child_thread;
+  int i;
+
+  signal (SIGUSR1, handler);
+  pthread_create (&child_thread, NULL, thread_function, NULL);
+  pthread_join (child_thread, NULL);
+
+  return 0;
+}
diff --git a/gdb/testsuite/gdb.threads/signal-command-handle-nopass.exp b/gdb/testsuite/gdb.threads/signal-command-handle-nopass.exp
new file mode 100644
index 0000000..3ea9cf8
--- /dev/null
+++ b/gdb/testsuite/gdb.threads/signal-command-handle-nopass.exp
@@ -0,0 +1,78 @@
+# 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/>.  */
+
+# Test that an explicit "signal FOO" delivers FOO even if "handle" for
+# that same signal is set to "nopass".  Also make sure the signal is
+# delivered to the right thread, even if GDB has to step over a
+# breakpoint in some other thread first.
+
+if [target_info exists gdb,nosignals] {
+    verbose "Skipping ${testfile}.exp because of nosignals."
+    return -1
+}
+
+standard_testfile
+
+if {[gdb_compile_pthreads "${srcdir}/${subdir}/${srcfile}" "${binfile}" \
+	 executable { debug }] != "" } {
+    return -1
+}
+
+# Run the test proper.  STEP_OVER indicates whether we leave in place
+# a breakpoint that needs to be stepped over when we explicitly
+# request a signal be delivered with the "signal" command.
+
+proc test { step_over } {
+    global srcfile binfile
+
+    with_test_prefix "step-over $step_over" {
+	clean_restart ${binfile}
+
+	if ![runto_main] then {
+	    fail "Can't run to main"
+	    return 0
+	}
+
+	gdb_test "handle SIGUSR1 stop print nopass"
+
+	gdb_test "b thread_function" "Breakpoint .* at .*$srcfile.*"
+	gdb_test "continue" "thread_function.*" "stopped in thread"
+
+	# Thread 2 is stopped at a breakpoint.  If we leave the
+	# breakpoint in place, GDB needs to move thread 2 past the
+	# breakpoint before delivering the signal to thread 1.  We
+	# want to be sure that GDB doesn't mistakenly deliver the
+	# signal to thread 1 while doing that.
+	if { $step_over == "no" } {
+	    delete_breakpoints
+	}
+
+	gdb_test "break handler" "Breakpoint .* at .*$srcfile.*"
+
+	gdb_test "thread 1" "Switching to thread 1.*"
+
+	set pattern "\\\* 1\[ \t\]+Thread.*"
+
+	gdb_test "info threads" $pattern "thread 1 selected"
+
+	gdb_test "signal SIGUSR1" "handler .*"
+
+	gdb_test "info threads" $pattern "thread 1 got the signal"
+    }
+}
+
+foreach stepover {"yes" "no"} {
+    test $stepover
+}
diff --git a/gdb/testsuite/gdb.threads/signal-command-multiple-signals-pending.c b/gdb/testsuite/gdb.threads/signal-command-multiple-signals-pending.c
new file mode 100644
index 0000000..2fc5f53
--- /dev/null
+++ b/gdb/testsuite/gdb.threads/signal-command-multiple-signals-pending.c
@@ -0,0 +1,98 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 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/>.  */
+
+#include <stdio.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <pthread.h>
+#include <signal.h>
+
+pthread_barrier_t barrier;
+sig_atomic_t got_sigusr1;
+sig_atomic_t got_sigusr2;
+
+void
+handler_sigusr1 (int sig)
+{
+  got_sigusr1 = 1;
+}
+
+void
+handler_sigusr2 (int sig)
+{
+  got_sigusr2 = 1;
+}
+
+void *
+thread_function (void *arg)
+{
+  volatile unsigned int count = 1;
+
+  pthread_barrier_wait (&barrier);
+
+  while (count++ != 0)
+    {
+      if (got_sigusr1 && got_sigusr2)
+	break;
+      usleep (1);
+    }
+}
+
+void
+all_threads_started (void)
+{
+}
+
+void
+all_threads_signalled (void)
+{
+}
+
+void
+end (void)
+{
+}
+
+int
+main (void)
+{
+  pthread_t child_thread[2];
+  int i;
+
+  signal (SIGUSR1, handler_sigusr1);
+  signal (SIGUSR2, handler_sigusr2);
+
+  pthread_barrier_init (&barrier, NULL, 3);
+
+  for (i = 0; i < 2; i++)
+    pthread_create (&child_thread[i], NULL, thread_function, NULL);
+
+  pthread_barrier_wait (&barrier);
+
+  all_threads_started ();
+
+  pthread_kill (child_thread[0], SIGUSR1);
+  pthread_kill (child_thread[1], SIGUSR2);
+
+  all_threads_signalled ();
+
+  for (i = 0; i < 2; i++)
+    pthread_join (child_thread[i], NULL);
+
+  end ();
+  return 0;
+}
diff --git a/gdb/testsuite/gdb.threads/signal-command-multiple-signals-pending.exp b/gdb/testsuite/gdb.threads/signal-command-multiple-signals-pending.exp
new file mode 100644
index 0000000..b5ec00a
--- /dev/null
+++ b/gdb/testsuite/gdb.threads/signal-command-multiple-signals-pending.exp
@@ -0,0 +1,166 @@
+# 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/>.  */
+
+# Test that "signal FOO" behaves correctly when we have multiple
+# threads that have stopped for a signal.
+
+if [target_info exists gdb,nosignals] {
+    verbose "Skipping ${testfile}.exp because of nosignals."
+    return -1
+}
+
+standard_testfile
+
+if {[gdb_compile_pthreads "${srcdir}/${subdir}/${srcfile}" "${binfile}" \
+	 executable { debug }] != "" } {
+    return -1
+}
+
+# Run the test proper.  SCHEDLOCK indicates which variant (around
+# scheduler-locking) of the test to perform.
+
+proc test { schedlock } {
+    global srcfile binfile
+
+    with_test_prefix "schedlock $schedlock" {
+	clean_restart ${binfile}
+
+	if ![runto_main] then {
+	    fail "Can't run to main"
+	    return 0
+	}
+
+	gdb_test "handle SIGUSR1 stop print pass"
+	gdb_test "handle SIGUSR2 stop print pass"
+
+	gdb_test "break all_threads_started" "Breakpoint .* at .*$srcfile.*"
+	gdb_test "continue" "all_threads_started.*"
+
+	# Using schedlock, let the main thread queue a signal for each
+	# non-main thread.
+	gdb_test_no_output "set scheduler-locking on"
+
+	gdb_test "break all_threads_signalled" "Breakpoint .* at .*$srcfile.*"
+	gdb_test "continue" "all_threads_signalled.*"
+
+	gdb_test "info threads" "\\\* 1\[ \t\]+Thread.*" "thread 1 selected"
+
+	# With schedlock still enabled, let each thread report its
+	# signal.
+
+	gdb_test "thread 3" "Switching to thread 3.*"
+	gdb_test "continue" "Program received signal SIGUSR2.*" "stop with SIGUSR2"
+	gdb_test "thread 2" "Switching to thread 2.*"
+	gdb_test "continue" "Program received signal SIGUSR1.*" "stop with SIGUSR1"
+
+	gdb_test "break handler_sigusr1" "Breakpoint .* at .*$srcfile.*"
+	gdb_test "break handler_sigusr2" "Breakpoint .* at .*$srcfile.*"
+
+	set handler_re "Breakpoint .*, handler_sigusr. \\(sig=.*\\) at .*"
+
+	# Now test the "signal" command with either scheduler locking
+	# enabled or disabled.
+
+	if { $schedlock == "off" } {
+	    # With scheduler locking off, switch to the main thread
+	    # and issue "signal 0".  "signal 0" should then warn that
+	    # two threads have signals that will be delivered.  When
+	    # we let the command proceed, a signal should be
+	    # delivered, and thus the corresponding breakpoint in the
+	    # signal handler should trigger.
+
+	    gdb_test_no_output "set scheduler-locking off"
+	    gdb_test "thread 1" "Switching to thread 1.*"
+
+	    set queried 0
+	    set test "signal command queries"
+	    gdb_test_multiple "signal 0" $test {
+		-re "stopped with.*stopped with.*stopped with.*Continue anyway.*y or n. $" {
+		    fail "$test (too many threads noted)"
+		    set queried 1
+		}
+		-re "stopped with signal SIGUSR.*\r\nContinuing .*still deliver .*Continue anyway.*y or n. $" {
+		    pass $test
+		    set queried 1
+		}
+		-re "Continue anyway.*y or n. $" {
+		    fail "$test (no threads noted)"
+		    set queried 1
+		}
+	    }
+
+	    # Continuing should stop in one of the signal handlers.
+	    # Which thread runs first is not determinate.
+	    if {$queried} {
+		gdb_test "y" "$handler_re" "one signal delivered"
+	    }
+
+	    # Continuing a second time should stop in the other
+	    # handler.
+	    with_test_prefix "second signal" {
+		gdb_test "continue" "$handler_re" "signal delivered"
+	    }
+	} else {
+	    # With scheduler locking on, stay with thread 2 selected,
+	    # and try to deliver its signal explicitly.  The "signal"
+	    # command should then warn that one other thread has a
+	    # signal that will be delivered.  When we let the command
+	    # proceed, the current thread's signal should be
+	    # delivered, and thus the corresponding breakpoint in the
+	    # signal handler should trigger.
+	    gdb_test "signal SIGUSR1" \
+		"Breakpoint .*, handler_sigusr1 \\(sig=.*\\) at .*" \
+		"signal command does not query, signal delivered"
+
+	    with_test_prefix "second signal" {
+		# The other thread had stopped for a signal too, and
+		# it wasn't resumed yet.  Disabling schedlock and
+		# trying "signal 0" from the main thread should warn
+		# again.
+		gdb_test_no_output "set scheduler-locking off"
+
+		set queried 0
+		set test "signal command queries"
+		gdb_test_multiple "signal 0" $test {
+		    -re "stopped with.*stopped with.*Continue anyway.*y or n. $" {
+			fail "$test (too many threads noted)"
+			set queried 1
+		    }
+		    -re "stopped with signal SIGUSR.*\r\nContinuing .*still deliver .*Continue anyway.*y or n. $" {
+			pass $test
+			set queried 1
+		    }
+		    -re "Continue anyway.*y or n. $" {
+			fail "$test (no threads noted)"
+			set queried 1
+		    }
+		}
+
+		if {$queried} {
+		    gdb_test "y" "Breakpoint .*, handler_sigusr2 \\(sig=.*\\) at .*" "signal delivered"
+		}
+	    }
+	}
+
+	# Both threads got their signal.  Continuing again should
+	# neither intercept nor deliver any other signal.
+	gdb_test "b end" "Breakpoint .* at .*$srcfile.*"
+	gdb_test "continue" "end .*" "no more signals"
+    }
+}
+
+foreach schedlock {"off" "on"} {
+    test $schedlock
+}
diff --git a/gdb/testsuite/gdb.threads/signal-delivered-right-thread.c b/gdb/testsuite/gdb.threads/signal-delivered-right-thread.c
new file mode 100644
index 0000000..66b68a8
--- /dev/null
+++ b/gdb/testsuite/gdb.threads/signal-delivered-right-thread.c
@@ -0,0 +1,61 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 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/>.  */
+
+#include <stdio.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <pthread.h>
+#include <signal.h>
+
+pthread_barrier_t barrier;
+
+void
+handler (int sig)
+{
+}
+
+void *
+thread_function (void *arg)
+{
+  pthread_barrier_wait (&barrier);
+
+  while (1)
+    usleep (1);
+}
+
+int
+main (void)
+{
+  pthread_t child_thread[2];
+  int i;
+
+  signal (SIGUSR1, handler);
+
+  pthread_barrier_init (&barrier, NULL, 3);
+
+  for (i = 0; i < 2; i++)
+    pthread_create (&child_thread[i], NULL, thread_function, NULL);
+
+  pthread_barrier_wait (&barrier);
+
+  pthread_kill (child_thread[0], SIGUSR1);
+
+  for (i = 0; i < 2; i++)
+    pthread_join (child_thread[i], NULL);
+
+  return 0;
+}
diff --git a/gdb/testsuite/gdb.threads/signal-delivered-right-thread.exp b/gdb/testsuite/gdb.threads/signal-delivered-right-thread.exp
new file mode 100644
index 0000000..4243495
--- /dev/null
+++ b/gdb/testsuite/gdb.threads/signal-delivered-right-thread.exp
@@ -0,0 +1,85 @@
+# 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/>.  */
+
+if [target_info exists gdb,nosignals] {
+    verbose "Skipping ${testfile}.exp because of nosignals."
+    return -1
+}
+
+standard_testfile
+
+if {[gdb_compile_pthreads "${srcdir}/${subdir}/${srcfile}" "${binfile}" \
+	 executable { debug }] != "" } {
+    return -1
+}
+
+# Run test proper.  COMMAND indicates whether to resume the inferior
+# with "signal 0" or "continue".
+
+proc test { command } {
+    global srcfile binfile
+
+    with_test_prefix "$command" {
+	clean_restart ${binfile}
+
+	if ![runto_main] then {
+	    fail "Can't run to main"
+	    return 0
+	}
+
+	gdb_test "handle SIGUSR1 stop print pass"
+
+	gdb_test "continue" "Program received signal SIGUSR1.*" "stop with SIGUSR1"
+
+	set pattern "\\\* 2\[ \t\]+Thread.*"
+
+	gdb_test "info threads" $pattern "thread 2 intercepted signal"
+
+	gdb_test "break handler" "Breakpoint .* at .*$srcfile.*"
+
+	gdb_test "thread 1" "Switching to thread 1.*"
+
+	if { $command == "continue" } {
+	    gdb_test "continue" "handler .*"
+	} elseif { $command == "signal 0" } {
+	    set queried 0
+	    set test "signal 0 queries"
+	    gdb_test_multiple "signal 0" $test {
+		-re "stopped with.*stopped with.*Continue anyway.*y or n. $" {
+		    fail "$test (multiple threads noted)"
+		    set queried 1
+		}
+		-re "stopped with signal SIGUSR1.*\r\nContinuing .*still deliver .*Continue anyway.*y or n. $" {
+		    pass $test
+		    set queried 1
+		}
+		-re "Continue anyway.*y or n. $" {
+		    fail "$test (no threads noted)"
+		    set queried 1
+		}
+	    }
+
+	    if {$queried} {
+		gdb_test "y" "handler .*" "signal is delivered"
+	    }
+	}
+
+	gdb_test "info threads" $pattern "thread 2 got the signal"
+    }
+}
+
+foreach command {"continue" "signal 0"} {
+    test $command
+}