[lldb-dev] [PATCH] Unexpected group-stop with threading under Linux

[Todd Fiala]

Verified this fixes it.  I'll go ahead and check it in.


On Mon, Jan 27, 2014 at 9:00 AM, Todd Fiala <tfiala at google.com> wrote:

> I'm giving this a shot now locally.  The change looks reasonable to me -
> any ptrace experts disagree?
>
> The one bit I'm not entirely sure about is: if assertions are disabled,
> and for some reason the WSTOPSIG(status) is not SIGSTOP (since we're not
> explicitly checking before the Resume(wait_pid, SIGSTOP) call), how badly
> can that gunk things up?  An if check before the Resume call would at least
> stop the wrong signal from getting sent to the inferior if I'm reading it
> right.
>
>
> On Mon, Jan 27, 2014 at 2:47 AM, Andrew MacPherson <andrew.macp at gmail.com>wrote:
>
>> This patch addresses a bug where in a multi-threaded program a new signal
>> from the inferior may be received before all group-stop messages from an
>> earlier signal have been handled. The attached .cpp file exposes the issue:
>>
>>    - clang++ -o thread thread.cpp -lpthread -g -O0
>>    - lldb ./thread
>>    - r
>>    - hit Ctrl-C
>>    - br set -f thread.cpp -l 11
>>    - c
>>    - <hang>
>>
>> A breakpoint is usually hit before all the group-stop messages involved
>> in restarting the process are handled and the internal state then gets out
>> of sync.
>>
>> The attached patch solves the issue and all unit tests pass, I'm not a
>> ptrace expert though so there may be a more appropriate fix. The group-stop
>> handling was taken from the existing ProcessMonitor::MonitorCallback.
>>
>> Thanks,
>>
>> Andrew
>>
>>
>>
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>>
>>
>
>
> --
> Todd Fiala | Software Engineer |  tfiala at google.com |  650-943-3180
>



-- 
Todd Fiala | Software Engineer | tfiala at google.com | 650-943-3180
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