From: Norton Allen <allen@huarp.harvard.edu>
To: Ken Brown <kbrown@cornell.edu>, cygwin <cygwin@cygwin.com>
Subject: Re: Unix Domain Socket Limitation?
Date: Mon, 30 Nov 2020 21:22:56 -0500 [thread overview]
Message-ID: <fb523694-7775-1d7a-db55-27ccbd6d157c@huarp.harvard.edu> (raw)
In-Reply-To: <85c9c70f-c016-0f88-099e-5c772adbc648@huarp.harvard.edu>
On 11/30/2020 9:14 PM, Norton Allen wrote:
> On 11/30/2020 6:19 PM, Ken Brown wrote:
>> On 11/30/2020 1:26 PM, Norton Allen wrote:
>>> On 11/30/2020 1:14 PM, Ken Brown wrote:
>>>> I can reproduce the hang, and it happens if I use the new AF_UNIX
>>>> code also. But what I'm seeing (at least with the new code) isn't
>>>> exactly what you describe.
>>>>
>>>> When the server's first select call returns, accept succeeds. The
>>>> server then calls select a second time, and that call doesn't
>>>> return. I haven't checked yet to see what's going on in the client,
>>>> and I may not get to that for a while.
>>>>
>>> That's good news, and seems to be consistent with my theory that it
>>> is some sort of race condition that might be particularly sensitive
>>> to system-specific timing. I am compiling cygwin1.dll now.
>>
>> Hi Norton,
>>
>> I think there's a mistake in your test program. Shouldn't
>> client_pselect() be waiting for the socket to be write-ready rather
>> than read-ready? Here's a quote from the Posix page for 'connect':
>>
>> If the connection cannot be established immediately and O_NONBLOCK is
>> set for the file descriptor for the socket, connect() shall fail and
>> set errno to [EINPROGRESS], but the connection request shall not be
>> aborted, and the connection shall be established asynchronously....
>>
>> When the connection has been established asynchronously, pselect(),
>> select(), and poll() shall indicate that the file descriptor for the
>> socket is ready for writing.
>>
> Yes, you are correct. In fact I had already fixed that bug on another
> branch, then forgot to update it on this one. I also noticed another
> bug in calculating width. Now I am not getting the blocking behavior
> but instead getting the wrong bits set in select(). I think I'd better
> pick this up in the morning when I am thinking straight!
Yeah, so now the example no longer blocks for me. Unfortunately these
bugs are not present in my application, so I will need to keep working
on this.
next prev parent reply other threads:[~2020-12-01 2:22 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-25 21:47 Norton Allen
2020-11-25 22:27 ` Ken Brown
[not found] ` <4260ad1b-4ab2-fa36-fd0e-7c9644560114@huarp.harvard.edu>
2020-11-26 17:13 ` Ken Brown
2020-11-30 17:19 ` Norton Allen
2020-11-30 18:14 ` Ken Brown
2020-11-30 18:26 ` Norton Allen
2020-11-30 23:19 ` Ken Brown
2020-12-01 2:14 ` Norton Allen
2020-12-01 2:22 ` Norton Allen [this message]
2020-12-02 17:30 ` Norton Allen
2020-12-04 1:11 ` Ken Brown
2020-12-04 13:51 ` Norton Allen
2020-12-05 23:52 ` Ken Brown
2020-12-06 17:17 ` Norton Allen
2020-12-06 22:32 ` Ken Brown
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