From: Garrick Staples <garrick@usc.edu>
Subject: Re: mountd segfault on itanium2
Date: Mon, 3 May 2004 17:17:18 -0700
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On Fri, Apr 30, 2004 at 08:07:30PM -0700, Garrick Staples alleged:
> On Fri, Apr 30, 2004 at 04:43:27PM -0700, Garrick Staples alleged:
> > I just spotted a pattern.  After collecting several strace samples, it =
always
> > segfaults after read() or write() to fd 5.  And fd 5 is always:
> >=20
> >    open("/proc/net/rpc/nfsd.fh/channel", O_RDWR) =3D 5
>=20
> I have an ugly work-around that seems to be working.  It seems that 2.6 h=
as a
> new nfs interface for userspace.  By forcing mountd to use the older 2.4
> interface, it doesn't segfault anymore.  So something in the new code pat=
hs is
> broken.

I'm slowly starting to wrap my brain around how these RPC calls work.  I've
found something that I can't make sense of.  In my_svc_run(), it packs fds =
3,
4, 5, 6, and 7 into select().  3, 4, and 5 are 3 files in /proc/net/rpc.  f=
d 6
 and 7 are udp and tcp sockets.  During my umount/mount tests, fd 6 is the
only set bit after the select(), and is then passed to svc_getreqset().

But just before the segfault, select() sets fd 5, which is
/proc/net/rpc/nfsd.fh/channel.  The thing that I don't understand is that f=
d 5
is being passed to svc_getreqset().  Shouldn't svc_getreqset() be only for =
fds
of sockets that have pending rpc calls?  Should fd 5 be cleared from the fd=
set
before calling svc_getreqset()?

--=20
Garrick Staples, Linux/HPCC Administrator
University of Southern California

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