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    Subject[PATCH RFC tip/core/rcu 15/41] rcu: Check for callback invocation from offline CPUs
    Date
    From: "Paul E. McKenney" <paul.mckenney@linaro.org>

    Because quiescent states are now reported from offline CPUs in
    CPU_DYING state, there is some possibility that such a CPU might
    note the end of a grace period and attempt to start invoking
    callbacks. This would be a very bad thing, and is supposed to
    be prevented by the fact that the CPU_DYING CPU gets rid of all
    its callbacks before reporting the quiescent state. However,
    there is other CPU-offline code in the kernel, and it is quite
    possible that someone will invoke RCU core processing from that
    code. Therefore, this commit adds a warning for this case.

    Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
    Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
    ---
    kernel/rcutree.c | 1 +
    1 files changed, 1 insertions(+), 0 deletions(-)

    diff --git a/kernel/rcutree.c b/kernel/rcutree.c
    index 9040cb6..03c0d5f 100644
    --- a/kernel/rcutree.c
    +++ b/kernel/rcutree.c
    @@ -1373,6 +1373,7 @@ static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp)
    * races with call_rcu() from interrupt handlers.
    */
    local_irq_save(flags);
    + WARN_ON_ONCE(cpu_is_offline(smp_processor_id()));
    bl = rdp->blimit;
    trace_rcu_batch_start(rsp->name, rdp->qlen_lazy, rdp->qlen, bl);
    list = rdp->nxtlist;
    --
    1.7.8


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