Re: RT and Cascade interrupts

[john cooper]

Ingo Molnar wrote:
> * john cooper <john.cooper@xxxxxxxxxxx> wrote:
> > The RPC code is attempting to replicate state of
> > timer ownership for a given rpc_task via RPC_TASK_HAS_TIMER
> > in rpc_task.tk_runstate.  Besides not working
> > correctly in the case of preemptable context it is
> > a replication of state of a timer pending in the
> > cascade structure (ie: timer->base).  The fix
> > changes the RPC code to use timer->base when
> > deciding whether an outstanding timer registration
> > exists during rpc_task tear down.
> >
> > Note: this failure occurred in the 40-04 version of
> > the patch though it applies to more current versions.
> > It was seen when executing stress tests on a number
> > of PPC targets running on an NFS mounted root though
> > was not observed on a x86 target under similar
> > conditions.
>
>
> should this fix go upstream too?

Yes.  The RPC code is attempting to replicate existing
and easily accessible state information in a timer
structure.  The simplistic means by which it does so
fails if ksoftirqd/rpc_run_timer() runs in preemptive
context.

-john


--
john.cooper@xxxxxxxxxxx
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