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Date: Fri, 15 Mar 2002 16:33:21 -0500
From: Christopher Faylor <cgf AT redhat DOT com>
To: cygwin AT cygwin DOT com
Subject: Re: Latest poll() hangs again (was Re: poll() bugs and patch)
Message-ID: <20020315213321.GA6540@redhat.com>
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References: <20020313181423 DOT C29574 AT cygbert DOT vinschen DOT de> <LOBBKDBPKEGJJFKNFHKBCEPEGJAA DOT boriss AT web DOT de> <20020314131554 DOT I29574 AT cygbert DOT vinschen DOT de> <20020315200120 DOT GA2484 AT tishler DOT net> <20020315221940 DOT J29574 AT cygbert DOT vinschen DOT de>
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On Fri, Mar 15, 2002 at 10:19:40PM +0100, Corinna Vinschen wrote:
>On Fri, Mar 15, 2002 at 03:01:21PM -0500, Jason Tishler wrote:
>> On Thu, Mar 14, 2002 at 01:15:54PM +0100, Corinna Vinschen wrote:
>> > Thanks for the patch.  I've applied it with some changes.
>> 
>> I was concerned when I first saw this patch.  Unfortunately, I just
>> tried it and my concerns were realized.
>> 
>> This patch causes poll() to hang again when only an invalid file
>> descriptor is specified.  See the following for a test case:
>> 
>>     http://sources.redhat.com/ml/cygwin-patches/2001-q3/msg00109.html
>> 
>> Please revert this patch or modify it so that poll() does not hang.
>
>I don't think reverting is the way to go.  One of the problems
>was that cygwin_select isn't called at all if all fd's are
>invalid, even if a timeout value is given.  Boris patch fixed
>that.  Unfortunately the problem you're describing is a border
>case which wasn't handled correctly by your patch as well, AFAICS.
>The correct solution would be to return immediately (aka
>cygwin_select isn't called) only if all fd's are invalid AND
>the timeout value is set to INFINITE (-1).
>
>Unfortunately SUSv2 doesn't handle that special case.  That's
>a pity.
>
>However, we could revert to handle invalid_fds again and then call
>cygwin_select only if timeout != -1.
>
>Comments?  Boris?  Jason?  Anybody else?

How does linux handle these cases?

cgf

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