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    Subject[tip:core/rcu] rcu: Add CPU-offline processing for single-node configurations
    Commit-ID:  33f76148ced0e0618062e302d2a9614efdbd4a06
    Gitweb: http://git.kernel.org/tip/33f76148ced0e0618062e302d2a9614efdbd4a06
    Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
    AuthorDate: Mon, 24 Aug 2009 09:42:01 -0700
    Committer: Ingo Molnar <mingo@elte.hu>
    CommitDate: Mon, 24 Aug 2009 20:37:04 +0200

    rcu: Add CPU-offline processing for single-node configurations

    Add preemptable-RCU plugin to handle the CPU-offline
    processing.

    An additional plugin is forthcoming to handle multinode RCU
    trees, but this current plugin works for configurations up to
    32 CPUs (64 CPUs for 64-bit kernels).

    Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
    Cc: laijs@cn.fujitsu.com
    Cc: dipankar@in.ibm.com
    Cc: akpm@linux-foundation.org
    Cc: mathieu.desnoyers@polymtl.ca
    Cc: josht@linux.vnet.ibm.com
    Cc: dvhltc@us.ibm.com
    Cc: niv@us.ibm.com
    Cc: peterz@infradead.org
    Cc: rostedt@goodmis.org
    LKML-Reference: <12511321213336-git-send-email->
    Signed-off-by: Ingo Molnar <mingo@elte.hu>


    ---
    kernel/rcutree.c | 2 ++
    kernel/rcutree_plugin.h | 24 ++++++++++++++++++++++++
    2 files changed, 26 insertions(+), 0 deletions(-)

    diff --git a/kernel/rcutree.c b/kernel/rcutree.c
    index cc02557..000b076 100644
    --- a/kernel/rcutree.c
    +++ b/kernel/rcutree.c
    @@ -84,6 +84,7 @@ extern long rcu_batches_completed_sched(void);
    static void cpu_quiet_msk(unsigned long mask, struct rcu_state *rsp,
    struct rcu_node *rnp, unsigned long flags);
    static void cpu_quiet_msk_finish(struct rcu_state *rsp, unsigned long flags);
    +static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp);
    static void __rcu_process_callbacks(struct rcu_state *rsp,
    struct rcu_data *rdp);
    static void __call_rcu(struct rcu_head *head,
    @@ -920,6 +921,7 @@ static void rcu_offline_cpu(int cpu)
    {
    __rcu_offline_cpu(cpu, &rcu_sched_state);
    __rcu_offline_cpu(cpu, &rcu_bh_state);
    + rcu_preempt_offline_cpu(cpu);
    }

    #else /* #ifdef CONFIG_HOTPLUG_CPU */
    diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
    index cd2ab67..201334c 100644
    --- a/kernel/rcutree_plugin.h
    +++ b/kernel/rcutree_plugin.h
    @@ -259,6 +259,18 @@ static int rcu_preempted_readers(struct rcu_node *rnp)
    return !list_empty(&rnp->blocked_tasks[rnp->gpnum & 0x1]);
    }

    +#ifdef CONFIG_HOTPLUG_CPU
    +
    +/*
    + * Do CPU-offline processing for preemptable RCU.
    + */
    +static void rcu_preempt_offline_cpu(int cpu)
    +{
    + __rcu_offline_cpu(cpu, &rcu_preempt_state);
    +}
    +
    +#endif /* #ifdef CONFIG_HOTPLUG_CPU */
    +
    /*
    * Check for a quiescent state from the current CPU. When a task blocks,
    * the task is recorded in the corresponding CPU's rcu_node structure,
    @@ -395,6 +407,18 @@ static int rcu_preempted_readers(struct rcu_node *rnp)
    return 0;
    }

    +#ifdef CONFIG_HOTPLUG_CPU
    +
    +/*
    + * Because preemptable RCU does not exist, it never needs CPU-offline
    + * processing.
    + */
    +static void rcu_preempt_offline_cpu(int cpu)
    +{
    +}
    +
    +#endif /* #ifdef CONFIG_HOTPLUG_CPU */
    +
    /*
    * Because preemptable RCU does not exist, it never has any callbacks
    * to check.

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