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    SubjectRe: suspicious RCU usage warnings in 3.3.0
    On Wed, Apr 11, 2012 at 09:03:19PM -0400, David Miller wrote:
    > From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
    > Date: Wed, 11 Apr 2012 17:45:07 -0700
    >
    > > On Wed, Apr 11, 2012 at 08:18:54PM -0400, David Miller wrote:
    > >> From: Stephen Hemminger <shemminger@vyatta.com>
    > >> Date: Wed, 11 Apr 2012 17:10:04 -0700
    > >>
    > >> > On Wed, 11 Apr 2012 16:08:37 -0700
    > >> > "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> wrote:
    > >> >
    > >> >> Hmmm... What CPU family is this running on? From the look of the
    > >> >> stack, it is sneaking out of idle into softirq without telling RCU.
    > >> >> This would cause RCU to complain bitterly about being invoked from
    > >> >> the idle loop -- and RCU ignores CPUs in the idle loop.
    > >> >>
    > >> >> Thanx, Paul
    > >> >
    > >> > Sun4... Ping David.
    > >>
    > >> So is there anything specific I need to do in the sparc64
    > >> idle loop?
    > >
    > > Hmmm... I must confess that I don't immediately see how control
    > > is passing from cpu_idle() in arch/sparc/kernel/process_64.c to
    > > __handle_softirq().
    > >
    > > But it looks like a simple function call in the call trace:
    >
    > It's coming from the trap return code path at the end of hardware
    > interrupt processing, on the IRQ stack.

    Ah! I should have guessed something like that was happening given
    that __handle_softirq() is written in assembly.

    Thanx, Paul



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