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Date:      Wed, 04 Apr 2018 14:34:51 +0000
From:      bugzilla-noreply@freebsd.org
To:        freebsd-bugs@FreeBSD.org
Subject:   [Bug 227285] File descriptor passing does not work reliably on SMP system (cache coherency issue?)
Message-ID:  <bug-227285-8-uOQD6WJwIk@https.bugs.freebsd.org/bugzilla/>
In-Reply-To: <bug-227285-8@https.bugs.freebsd.org/bugzilla/>
References:  <bug-227285-8@https.bugs.freebsd.org/bugzilla/>

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D227285

--- Comment #2 from Jan Kokem=C3=BCller <jan.kokemueller@gmail.com> ---
Created attachment 192214
  --> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=3D192214&action=
=3Dedit
excerpt of Dtrace script output

Here is part of the Dtrace debug log.

When 'got err' is printed it means that the parent could not read the byte =
from
the child. At this point the address of the receive sockbuf is
'fffff801071df148' and the SBS_CANTRCVMORE flag is set (CPU 1).

However, further above, this sockbuf looks fine in the child (CPU 3) and th=
ere
aren't any calls to socantrcvmore_locked() in the meantime.

Even further above, this sockbuf was destroyed by the parent in a previous
iteration (CPU 1) and therefore SBS_CANTRCVMORE is set. But this should not
affect the current iteration. It looks like the memory from the child proce=
ss
on CPU 3 isn't made visible to CPU 1 properly.

--=20
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