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Re: how can the nfs timer work?
On Sat, Dec 13, 2008 at 01:56:28PM +0000, Andrew Doran wrote:
> On Thu, Dec 11, 2008 at 01:55:33AM +0200, Antti Kantee wrote:
> > I've been trying to figure out why the nfs timer (nfs_timer() in
> > nfs_socket.c) works.
> > 1) I don't really see what good splsoftnet does, as the queue is
> > never messed with in network interrupt context AFAICT. Even if
> > this holds for the queue, there is nothing protecting the actual
> > requests apart from biglock.
> That is a problem. There is work on a branch to make the nfs client MPSAFE.
> > 2) It does a call to solock(), which pretty clearly can block and
> > therefore the request currently being processed can be invalidated
> > and freed during the call to solock(). (are callouts even allowed
> > to block??)
> Callouts can block, yup.
> > But I'm really curious why this doesn't trigger in the kernel pretty much
> > instantly.
A workaround appropriate for 5.0 would be to take softnet_lock around the
entire loop, and comment out the solock/sounlock calls. This would lock all
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