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From:   "Randall S. Becker" <rsbecker@nexbridge.com>
To:     <git@vger.kernel.org>
Subject: [Bug/Solution] Git hangs in compat/poll/poll.c on HPE NonStop
Date:   Thu, 28 Sep 2017 17:01:27 -0400
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Hi Team,

After a whole lot of investigating, we (it is a large "we") have discovered
the reason for the hang we occasionally get in git-upload-pack on HPE
NonStop servers - reported here well over a year ago. This resulted from a
subtle check that the operating system does on file descriptors. When it
sees random values in pfd[i].revents, it sometimes thinks its dealing with a
TTY and well, things end badly after that. There is a non-destructive fix
that I would like to propose for this that I have already tested. Sadly, I
have no email mechanism where our repo resides for a real patch message. The
patch is based on 2.3.7 (16018ae), but should be applicable forward. We have
held off moving to a more recent version until resolving this, so that's
next on our plan.

--- a/compat/poll/poll.c
+++ b/compat/poll/poll.c
@@ -438,6 +438,10 @@ poll (struct pollfd *pfd, nfds_t nfd, int timeout)
            pfd[i].revents = happened;
            rc++;
          }
+        else
+          {
+            pfd[i].revents = 0;
+          }
       }

   return rc;

Sincerely,
Randall

-- Brief whoami: NonStop&UNIX developer since approximately
UNIX(421664400)/NonStop(211288444200000000) 
-- In my real life, I talk too much.