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Subject: Re: Sv: Sv: Sv: Sv: Named pipes and multiple writers
To: sten.kristian.ivarsson@gmail.com
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From: Ken Brown via Cygwin <cygwin@cygwin.com>
Reply-To: Ken Brown <kbrown@cornell.edu>
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On 3/28/2020 8:10 AM, sten.kristian.ivarsson@gmail.com wrote:
>> On 3/27/2020 10:53 AM, sten.kristian.ivarsson@gmail.com wrote:
>>>> On 3/26/2020 7:19 PM, Ken Brown via Cygwin wrote:
>>>>> On 3/26/2020 6:39 PM, Ken Brown via Cygwin wrote:
>>>>>> On 3/26/2020 6:01 PM, sten.kristian.ivarsson@gmail.com wrote:
>>>>>>> The ENIXIO occurs when parallel child-processes simultaneously
>>>>>>> using O_NONBLOCK opening the descriptor.
>>>>>>
>>>>>> This is consistent with my guess that the error is generated by
>>>>>> fhandler_fifo::wait.  I have a feeling that read_ready should have
>>>>>> been created as a manual-reset event, and that more care is needed
>>>>>> to make sure it's set when it should be.
>>>>>>
>>>>>>> I could provide a code-snippet
>>>>>>> to reproduce it if wanted ?
>>>>>>
>>>>>> Yes, please!
>>>>>
>>>>> That might not be necessary.  If you're able to build the git repo
>>>>> master branch, please try the attached patch.
>>>
>>>> Here's a better patch.
>>>
>>>
>>> I finally succeeded to build latest master (make is not my favourite
>>> tool) and added the patch, but still no success in my little
>>> test-program (see
>>> attachment) when creating a write-file-descriptor with O_NONBLOCK
> 
>> Your test program fails for me on Linux too.  Here's the output from one
> run:
> 
> You're right. That was extremely careless of me to not test this in Linux
> first :-)

No problem.

> I can assure that we have a use case that works on Linux but not in Cygwin,
> but it seems like I failed to narrow it down in the wrong way
> 
> I'll try to rearrange my code (that works in Linux) to mimic our application
> but in a simple way (I'll be back)

OK, I'll be waiting for you.  BTW, if it's not too hard to write your test case 
in plain C, or at least less modern C++, that would simplify things for me.  For 
example, your pipe.cpp failed to compile on one Linux machine I wanted to test 
it on, presumably because that machine had an older C++ compiler.

Ken
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