[lldb-dev] Resuming traced process on Linux and SIGSTOP

[Andrew MacPherson]

Great, thanks Todd!


On Tue, Mar 25, 2014 at 8:09 PM, Todd Fiala <tfiala at google.com> wrote:

> I just finished clearing out some Linux test errors (I'm now all green on
> Linux x86_64).  I'll add this to a queue I've got with some changes from
> Piotr, Ed and you in it now.
>
>
> On Tue, Mar 25, 2014 at 12:08 PM, Andrew MacPherson <andrew.macp at gmail.com
> > wrote:
>
>> Just pinging this again in case anyone has a chance to review the small
>> Linux detach patch here. Thanks!
>>
>>
>> On Sat, Mar 22, 2014 at 11:05 AM, Andrew MacPherson <
>> andrew.macp at gmail.com> wrote:
>>
>>> I'm attaching a patch here that resolves the issue of a signal being
>>> delivered to the inferior on detach, let me know if I should start a new
>>> thread for this but since it's related to what we were discussing I'm
>>> attaching it here. To reproduce the issue just launch a process, then in a
>>> new terminal:
>>>
>>> sudo lldb -p <pid>
>>> c
>>> q
>>>
>>> When quitting the inferior receives a SIGSTOP because the process is
>>> already running when the PTRACE_DETACH is sent. I can't find a clear answer
>>> on what's supposed to happen here (PTRACE_DETACH sent to running thread)
>>> but this is the behaviour I'm seeing. The docs do indicate that
>>> PRACE_DETACH is like PTRACE_CONT and should only be sent to a stopped
>>> thread.
>>>
>>> I also tried to add a unit test for this and the previous patch, however
>>> I hit http://llvm.org/pr16172. The tests these two patches require are
>>> similar to the one mentioned in that case and I get the same errors in my
>>> sample test as when running that one:
>>>
>>> attach -p <pid> (ok)
>>> c (ok)
>>> detach (error: Detach failed: No such process)
>>>
>>> And:
>>>
>>> attach -p <pid> (ok)
>>> c (ok)
>>> process interrupt (ok)
>>> c (error: Failed to resume process: Resume request failed - process
>>> still running..)
>>>
>>>
>>> On Fri, Mar 21, 2014 at 8:37 PM, Ed Maste <emaste at freebsd.org> wrote:
>>>
>>>> On 21 March 2014 15:14,  <jingham at apple.com> wrote:
>>>> > I'm pretty sure we have some test cases that test attach.  If we
>>>> don't, then it would be great to add one.  If we do, then it would be
>>>> interesting to see why they didn't fail.  For instance, maybe they just
>>>> didn't bother to try "continue" after the attach.  Just adding that would
>>>> be good too.
>>>>
>>>> We definitely have some, because they used to fail early on in the
>>>> FreeBSD porting effort.  I suspect that your suggestion is correct and
>>>> they just don't do anything but attach and then quit.
>>>>
>>>> On a related note, I'm pretty sure we don't have tests for detach.
>>>> I'll see about extending tests to include that at some point.
>>>>
>>>> -Ed
>>>>
>>>
>>>
>>
>
>
> --
>  Todd Fiala | Software Engineer |  tfiala at google.com |  650-943-3180
>
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