preferred kernel upcall method to master nfsd

John Baldwin jhb at
Mon Nov 22 21:29:40 UTC 2010

On Monday, November 22, 2010 10:04:27 am Ivan Voras wrote:
> On 11/22/10 15:28, John Baldwin wrote:
> > On Monday, November 22, 2010 8:19:32 am Rick Macklem wrote:
> >> Hi,
> >>
> >> The experimental NFSv4 server in the kernel needs to tell the master nfsd when
> >> to make a backup copy of the stable restart file. I know how to do this using a
> >> signal, but is there a better/preferred way under FreeBSD-current?
> >
> > A signal sounds like the simplest approach to me.
> Signals work for processes inside the kernel? How? The scheduler 
> preempts them and does magic when deciding where to continue running them?

nfsd is a user process.  I suspect that when it receives a signal it falls out of
nfssvc() with EINTR and handles saving the restart file in userland.  Is that close
to the process Rick or does you need to send a signal between threads that are
exclusively within the kernel?

John Baldwin

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