[Bug breakpoints/15693] New: Extra *running event when call-style dprintf hits

[Bug breakpoints/15693] New: Extra *running event when call-style dprintf hits

[marc.khouzam at ericsson dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=15693

            Bug ID: 15693
           Summary: Extra *running event when call-style dprintf hits
           Product: gdb
           Version: HEAD
            Status: NEW
          Severity: normal
          Priority: P2
         Component: breakpoints
          Assignee: unassigned at sourceware dot org
          Reporter: marc.khouzam at ericsson dot com

With HEAD of June 27 which has the fix to Bug 15075, I'm seeing an un-expected
*running event each time a dprintf is hit in the dprintf-style 'call'.

Here is an cleaned up session showing the problem:

> gdb.7.7 -i mi loopfirst
=thread-group-added,id="i1"
~"GNU gdb (GDB) 7.6.50.20130627-cvs\n"

(gdb) -dprintf-insert 8 "hello\n"
^done,bkpt={number="1",type="dprintf",disp="keep",enabled="y",addr="0x0000000000400570",func="main()",file="loopfirst.cc",fullname="/home/lmckhou/testing/loopfirst.cc",line="8",thread-groups=["i1"],times="0",script={"printf
\"hello\\n\""},original-location="/home/lmckhou/testing/loopfirst.cc:8"}

(gdb) set dprintf-style call
&"set dprintf-style call\n"
=breakpoint-modified,bkpt={number="1",type="dprintf",disp="keep",enabled="y",addr="0x0000000000400570",func="main()",file="loopfirst.cc",fullname="/home/lmckhou/testing/loopfirst.cc",line="8",thread-groups=["i1"],times="0",script={"call
(void) printf
(\\"hello\\\\n\\")"},original-location="/home/lmckhou/testing/loopfirst.cc:8"}
=cmd-param-changed,param="dprintf-style",value="call"
^done

(gdb) -exec-run
=thread-group-started,id="i1",pid="6627"
=thread-created,id="1",group-id="i1"
^running
*running,thread-id="all"
(gdb) 
[...]
=breakpoint-modified,bkpt={number="1",type="dprintf",disp="keep",enabled="y",addr="0x0000000000400570",func="main()",file="loopfirst.cc",fullname="/home/lmckhou/testing/loopfirst.cc",line="8",thread-groups=["i1"],times="1",script={"call
(void) printf
(\\"hello\\\\n\\")"},original-location="/home/lmckhou/testing/loopfirst.cc:8"}
hello
*running,thread-id="1"

=> we can see this extra *running event, which is not seen when using the 'gdb'
dprintf-style.

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[Bug breakpoints/15693] Extra *running event when call-style dprintf hits

[palves at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=15693

Pedro Alves <palves at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |palves at redhat dot com

--- Comment #1 from Pedro Alves <palves at redhat dot com> ---
Yeah, you'll this for all infcalls, not just dprintf+call.  E.g., with
something like:

#include <unistd.h>
#include <stdlib.h>

int
return_false (void)
{
  return 0;
}

int
main ()
{
  while (1)
    usleep (1);
}

$ gdb return-false -i=mi

(gdb) 
start
...
(gdb) 
b 14 if return_false ()
&"b 14 if return_false ()\n"
~"Breakpoint 2 at 0x4004eb: file return-false.c, line 14.\n"
...
^done
(gdb) 
c
&"c\n"
~"Continuing.\n"
^running
*running,thread-id="1"
(gdb) 
*running,thread-id="1"
*running,thread-id="1"
*running,thread-id="1"
*running,thread-id="1"
*running,thread-id="1"
*running,thread-id="1"
... repeat forever ...

We should be suppressing that if we never told the user/frontend the thread was
stopped.

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[Bug breakpoints/15693] Extra *running event when call-style dprintf hits

[marc.khouzam at ericsson dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=15693

--- Comment #2 from Marc Khouzam <marc.khouzam at ericsson dot com> ---
(In reply to Pedro Alves from comment #1)
> Yeah, you'll this for all infcalls, not just dprintf+call.
[...]
>(gdb) b 14 if return_false ()

That is interesting.  If there is an infcall that causes a bp to be skipped, we
see this extra *running event.
But if it is not an infcall and the bp is still skipped (due to some other
condition), we don't see the event.

> We should be suppressing that if we never told the user/frontend the thread
> was stopped.

Nicer.  Thanks.

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[Bug breakpoints/15693] Extra *running event when call-style dprintf hits

[palves at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=15693

--- Comment #3 from Pedro Alves <palves at redhat dot com> ---
> That is interesting.  If there is an infcall that causes a bp to be skipped, 
> we see this extra *running event.
> But if it is not an infcall and the bp is still skipped (due to some other
> condition), we don't see the event.

Indeed.  We also have:

static void
mi_on_resume (ptid_t ptid)
{
  struct thread_info *tp = NULL;

  if (ptid_equal (ptid, minus_one_ptid) || ptid_is_pid (ptid))
    tp = inferior_thread ();
  else
    tp = find_thread_ptid (ptid);

  /* Suppress output while calling an inferior function.  */
  if (tp->control.in_infcall)
    return;


In the non-infcall case, the thread is never marked THREAD_STOPPED, so
set_running never ends up letting the MI observer known a thread was started.

However, if an infcall is involved, then when the infcall finishes, the
normal_stop ends up making the thread state be THREAD_STOPPED:

(top-gdb) bt
#0  0x00000000005dfc87 in finish_thread_state (ptid=...) at
../../src/gdb/thread.c:723
#1  0x00000000005dfdcf in finish_thread_state_cleanup (arg=0xc51a00) at
../../src/gdb/thread.c:750
#2  0x0000000000571474 in do_my_cleanups (pmy_chain=0xc4c630,
old_chain=0xf194c0) at ../../src/gdb/cleanups.c:155
#3  0x00000000005714e1 in do_cleanups (old_chain=0xf194c0) at
../../src/gdb/cleanups.c:177
#4  0x00000000005d3476 in normal_stop () at ../../src/gdb/infrun.c:6040
#5  0x00000000005cbb12 in proceed (addr=18446744073709551615,
siggnal=GDB_SIGNAL_DEFAULT, step=0) at ../../src/gdb/infrun.c:2342
#6  0x00000000005c3e24 in continue_1 (all_threads=0) at
../../src/gdb/infcmd.c:726
#7  0x00000000005c409b in continue_command (args=0x0, from_tty=1) at
../../src/gdb/infcmd.c:818
#8  0x00000000004dc5cf in do_cfunc (c=0xd380b0, args=0x0, from_tty=1) at
../../src/gdb/cli/cli-decode.c:113
#9  0x00000000004df664 in cmd_func (cmd=0xd380b0, args=0x0, from_tty=1) at
../../src/gdb/cli/cli-decode.c:1888
#10 0x00000000006e4425 in execute_command (p=0x7fffffffd341 "", from_tty=1) at
../../src/gdb/top.c:489


However, we don't want that in an infcall -- from the frontend's and user's
perspective the thread was nver THREAD_STOPPED.  Sounds like then the fix is to
do the suppressing in the normal_stop/THREAD_STOPPED path, not on the
"set_running" path.

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[Bug breakpoints/15693] Extra *running event when call-style dprintf hits

[teawater at gmail dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=15693

teawater <teawater at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
                 CC|                            |teawater at gmail dot com
           Assignee|unassigned at sourceware dot org   |teawater at gmail dot com

--- Comment #4 from teawater <teawater at gmail dot com> ---
http://sourceware.org/ml/gdb-patches/2013-07/msg00222.html

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[Bug breakpoints/15693] Extra *running event when call-style dprintf hits

[palves at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=15693

Pedro Alves <palves at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|teawater at gmail dot com          |palves at redhat dot com

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[Bug breakpoints/15693] Extra *running event when call-style dprintf hits

[palves at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=15693

Pedro Alves <palves at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED
   Target Milestone|---                         |7.8

--- Comment #5 from Pedro Alves <palves at redhat dot com> ---
Fixed:

https://sourceware.org/ml/gdb-patches/2014-05/msg00273.html

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