Re: Spinlocking patch for in xprt.c

[Trond Myklebust <trond.myklebust@fys.uio.no>]

>>>>> " " == David S Miller <davem@redhat.com> writes:

     > Trond, did you actually look at how this code works before you
     > made modifications to my fixes?

     > xprt_lock serializes sleep/wakeup sequences in the xprt code,
     > so you cannot remove xprt_lock from the sections where I added
     > holding of xprt_sock_lock to protect the state of
     > xprt->snd_task.  So for example, this part of your patch is
     > completely bogus and will create new corruptions and crashes:

IIRC xprt_lock is there for 2 purposes:

  - serialize access to the TCP connect code
  - gate access to the *socket* via the xprt_(up|down)_transmit() (and
    hence setting xprt->snd_task which is a pointer to the task that
    currently is allowed to access the socket.)

Those 2 tasks are completely orthogonal to one another, so we should
be quite free to drop xprt_lock in the second case.

I can see no other places where we're using xprt_lock to protect a
sleep/wakeup of xprt->snd_task unless you're introducing it? If so for
what purpose?

Cheers,
  Trond
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