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Message-ID: <15698.59577.788998.300262@charged.uio.no>
Date: Thu, 8 Aug 2002 23:55:05 +0200
To: Dave McCracken <dmccr@us.ibm.com>
Cc: trond.myklebust@fys.uio.no, Linux Kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 2.5.30+] Second attempt at a shared credentials patch
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From: Trond Myklebust <trond.myklebust@fys.uio.no>
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>>>>> " " == Dave McCracken <dmccr@us.ibm.com> writes:

     > --On Thursday, August 08, 2002 09:56:23 PM +0200 Trond
     > Myklebust <trond.myklebust@fys.uio.no> wrote:

    >> ... which begs the question: are you saying that there are no
    >> SMP issues with CLONE_CRED and setting/reading the 'struct
    >> cred' members?

     > Yes, I'm saying there are no SMP issues with the shared cred
     > structure.  I looked for them and failed to find any.
     > Credentials are not set cross-task, and are always done via
     > atomic ops.  I also failed to find any broader race conditions
     > that would require a lock.

What if one thread is doing an RPC call while the other is changing
the 'groups' entry?

Given that the first thread wants both to copy and/or compare the
groups entry what prevents scenarios of the form?

  Thread 1                       Thread 2

                                change cred->ngroups
  copy cred->ngroups
  copy cred->groups
                                change cred->groups


Cheers,
  Trond
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