diff mbox

Remove a spurious target_terminal::ours() from windows_nat_target::wait()

Message ID 20180802165357.176928-1-jon.turney@dronecode.org.uk
State New
Headers show

Commit Message

Jon TURNEY Aug. 2, 2018, 4:53 p.m. UTC
This causes the inferior to stop with SIGTTIN if it tries to read from the
terminal after it has been continued.

See https://cygwin.com/ml/cygwin/2016-09/msg00285.html for reproduction.

Since MinGW doesn't have a tcsetpgrp(), I don't think this problem would be
observed there, but Cygwin does so target_terminal::ours() will call it.

Calling target_terminal::ours() here seems to be is no longer appropriate
after the "Merge async and sync code paths" changes (as the inferior is now
in a separate process group even in sync mode(?), which is always used on
Windows targets)

This call was added in commit c44537cf (and see
https://sourceware.org/ml/gdb-patches/2007-02/msg00167.html for what it
fixed, which is not regressed by this change)

When windows_nat_target::wait() is entered, the inferior is running (either
it's been just been started or attached to, or windows_continue() was
called), so grabbing the controlling terminal away from it here seems to be
wrong, since infrun.c takes care of calling target_terminal::ours() when the
inferior stops.

gdb/ChangeLog:

2018-08-02  Jon Turney  <jon.turney@dronecode.org.uk>

	* windows-nat.c (windows_nat_target::wait): Remove a spurious
	target_terminal::ours().
---
 gdb/windows-nat.c | 2 --
 1 file changed, 2 deletions(-)

Comments

Simon Marchi Aug. 7, 2018, 2:45 a.m. UTC | #1
On 2018-08-02 12:53, Jon Turney wrote:
> This causes the inferior to stop with SIGTTIN if it tries to read from 
> the
> terminal after it has been continued.
> 
> See https://cygwin.com/ml/cygwin/2016-09/msg00285.html for 
> reproduction.
> 
> Since MinGW doesn't have a tcsetpgrp(), I don't think this problem 
> would be
> observed there, but Cygwin does so target_terminal::ours() will call 
> it.
> 
> Calling target_terminal::ours() here seems to be is no longer 
> appropriate
> after the "Merge async and sync code paths" changes (as the inferior is 
> now
> in a separate process group even in sync mode(?), which is always used 
> on
> Windows targets)
> 
> This call was added in commit c44537cf (and see
> https://sourceware.org/ml/gdb-patches/2007-02/msg00167.html for what it
> fixed, which is not regressed by this change)
> 
> When windows_nat_target::wait() is entered, the inferior is running 
> (either
> it's been just been started or attached to, or windows_continue() was
> called), so grabbing the controlling terminal away from it here seems 
> to be
> wrong, since infrun.c takes care of calling target_terminal::ours() 
> when the
> inferior stops.
> 
> gdb/ChangeLog:
> 
> 2018-08-02  Jon Turney  <jon.turney@dronecode.org.uk>
> 
> 	* windows-nat.c (windows_nat_target::wait): Remove a spurious
> 	target_terminal::ours().

This seems good to me, but I'd rather check with Pedro, since he knows 
this stuff much better.

Simon
Pedro Alves Aug. 9, 2018, 1:23 p.m. UTC | #2
On 08/07/2018 03:45 AM, Simon Marchi wrote:
> On 2018-08-02 12:53, Jon Turney wrote:
>> This causes the inferior to stop with SIGTTIN if it tries to read from the
>> terminal after it has been continued.
>>
>> See https://cygwin.com/ml/cygwin/2016-09/msg00285.html for reproduction.
>>
>> Since MinGW doesn't have a tcsetpgrp(), I don't think this problem would be
>> observed there, but Cygwin does so target_terminal::ours() will call it.
>>
>> Calling target_terminal::ours() here seems to be is no longer appropriate
>> after the "Merge async and sync code paths" changes (as the inferior is now
>> in a separate process group even in sync mode(?), which is always used on
>> Windows targets)

I don't really understand what the async/sync code paths changes
here, but regardless ...

>>
>> This call was added in commit c44537cf (and see
>> https://sourceware.org/ml/gdb-patches/2007-02/msg00167.html for what it
>> fixed, which is not regressed by this change)
>>
>> When windows_nat_target::wait() is entered, the inferior is running (either
>> it's been just been started or attached to, or windows_continue() was
>> called), so grabbing the controlling terminal away from it here seems to be
>> wrong, since infrun.c takes care of calling target_terminal::ours() when the
>> inferior stops.
>>
>> gdb/ChangeLog:
>>
>> 2018-08-02  Jon Turney  <jon.turney@dronecode.org.uk>
>>
>>     * windows-nat.c (windows_nat_target::wait): Remove a spurious
>>     target_terminal::ours().
> 
> This seems good to me, but I'd rather check with Pedro, since he knows this stuff much better.

... this LGTM.

Thanks,
Pedro Alves
Jon TURNEY Sept. 23, 2018, 3:24 p.m. UTC | #3
On 09/08/2018 14:23, Pedro Alves wrote:
> On 08/07/2018 03:45 AM, Simon Marchi wrote:
>> On 2018-08-02 12:53, Jon Turney wrote:
>>> This causes the inferior to stop with SIGTTIN if it tries to read from the
>>> terminal after it has been continued.
>>>
>>> See https://cygwin.com/ml/cygwin/2016-09/msg00285.html for reproduction.
>>>
>>> Since MinGW doesn't have a tcsetpgrp(), I don't think this problem would be
>>> observed there, but Cygwin does so target_terminal::ours() will call it.
>>>
>>> Calling target_terminal::ours() here seems to be is no longer appropriate
>>> after the "Merge async and sync code paths" changes (as the inferior is now
>>> in a separate process group even in sync mode(?), which is always used on
>>> Windows targets)
> 
> I don't really understand what the async/sync code paths changes
> here, but regardless ...

Me neither.  Ideally I would have noticed this regression closer to the 
time those changes were made, but...

>>> This call was added in commit c44537cf (and see
>>> https://sourceware.org/ml/gdb-patches/2007-02/msg00167.html for what it
>>> fixed, which is not regressed by this change)
>>>
>>> When windows_nat_target::wait() is entered, the inferior is running (either
>>> it's been just been started or attached to, or windows_continue() was
>>> called), so grabbing the controlling terminal away from it here seems to be
>>> wrong, since infrun.c takes care of calling target_terminal::ours() when the
>>> inferior stops.
>>>
>>> gdb/ChangeLog:
>>>
>>> 2018-08-02  Jon Turney  <jon.turney@dronecode.org.uk>
>>>
>>>      * windows-nat.c (windows_nat_target::wait): Remove a spurious
>>>      target_terminal::ours().
>>
>> This seems good to me, but I'd rather check with Pedro, since he knows this stuff much better.
> 
> ... this LGTM.

Thanks.

    0c0a40e0ab..a44294f5ed  master -> master
diff mbox

Patch

diff --git a/gdb/windows-nat.c b/gdb/windows-nat.c
index aea502638e..40cc224805 100644
--- a/gdb/windows-nat.c
+++ b/gdb/windows-nat.c
@@ -1703,8 +1703,6 @@  windows_nat_target::wait (ptid_t ptid, struct target_waitstatus *ourstatus,
 {
   int pid = -1;
 
-  target_terminal::ours ();
-
   /* We loop when we get a non-standard exception rather than return
      with a SPURIOUS because resume can try and step or modify things,
      which needs a current_thread->h.  But some of these exceptions mark