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Message-ID:	<009601c13e6d$c4466670$0200a8c0@lifelesswks>
From:	"Robert Collins" <robert DOT collins AT itdomain DOT com DOT au>
To:	<cygwin-developers AT cygwin DOT com>
References:	<20010915234433 DOT A30407 AT redhat DOT com>
Subject:	Re: possible explanation for make hang
Date:	Sun, 16 Sep 2001 15:09:29 +1000
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----- Original Message -----
From: "Christopher Faylor" <cgf AT redhat DOT com>
To: <cygwin-developers AT cygwin DOT com>
Sent: Sunday, September 16, 2001 1:44 PM
Subject: possible explanation for make hang


> I don't know precisely what make is doing but it is possible that
> if more than one program is attempting to read from the same pipe
> there will be a race that will cause cygwin to block in an
uninterruptible
> read.  So, if something like a SIGCHLD comes in while cygwin is
reading
> a pipe it won't be possible to deal with it.  I'm not aware of any
> way to interrupt a blocking read on a pipe so cygwin will hang until
> something shows up on the pipe.

Can we wait on the pipe and a signal event?
Ie
==
HANDLE handles[2];
handles[0] = signalevent;
handles[1] = pipe;
dword rc = WaitForMultipleObjects (2, handles, FALSE, INFINITE);
if ((rc - WAIT_OBJECT_0) == 1)
  ReadFile (pipe);
else
  handle_signal;
  /* the pipe may also have data, but can check again once the signal is
handled*/
==

> I just had this happen to me after 57 iterations of make in the winsup
> directory.  The stack traces of the affected makes seemed to indicate
> that this is what is happening.
>
> I *really* wish I knew of another way to deal with interrupting reads
> than the kludge that is now in use but I don't.
>
> I thought I had a promising lead a few weeks ago but the Windows API
> stood staunchly in my path, as usual.

What was that? Perhaps a brain storm could find something?

Rob

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