lkml.org 
[lkml]   [2012]   [Feb]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH tip/core/rcu 46/47] rcu: Add RCU_NONIDLE() for idle-loop RCU read-side critical sections
    Date
    From: "Paul E. McKenney" <paul.mckenney@linaro.org>

    RCU, RCU-bh, and RCU-sched read-side critical sections are forbidden
    in the inner idle loop, that is, between the rcu_idle_enter() and the
    rcu_idle_exit() -- RCU will happily ignore any such read-side critical
    sections. However, things like powertop need tracepoints in the inner
    idle loop.

    This commit therefore provides an RCU_NONIDLE() macro that can be used to
    wrap code in the idle loop that requires RCU read-side critical sections.

    Suggested-by: Steven Rostedt <rostedt@goodmis.org>
    Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
    Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
    Reviewed-by: Josh Triplett <josh@joshtriplett.org>
    Acked-by: Deepthi Dharwar <deepthi@linux.vnet.ibm.com>
    ---
    include/linux/rcupdate.h | 27 +++++++++++++++++++++++++++
    kernel/rcutiny.c | 2 ++
    kernel/rcutree.c | 2 ++
    3 files changed, 31 insertions(+), 0 deletions(-)

    diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
    index 6ee663c..9372174 100644
    --- a/include/linux/rcupdate.h
    +++ b/include/linux/rcupdate.h
    @@ -190,6 +190,33 @@ extern void rcu_idle_exit(void);
    extern void rcu_irq_enter(void);
    extern void rcu_irq_exit(void);

    +/**
    + * RCU_NONIDLE - Indicate idle-loop code that needs RCU readers
    + * @a: Code that RCU needs to pay attention to.
    + *
    + * RCU, RCU-bh, and RCU-sched read-side critical sections are forbidden
    + * in the inner idle loop, that is, between the rcu_idle_enter() and
    + * the rcu_idle_exit() -- RCU will happily ignore any such read-side
    + * critical sections. However, things like powertop need tracepoints
    + * in the inner idle loop.
    + *
    + * This macro provides the way out: RCU_NONIDLE(do_something_with_RCU())
    + * will tell RCU that it needs to pay attending, invoke its argument
    + * (in this example, a call to the do_something_with_RCU() function),
    + * and then tell RCU to go back to ignoring this CPU. It is permissible
    + * to nest RCU_NONIDLE() wrappers, but the nesting level is currently
    + * quite limited. If deeper nesting is required, it will be necessary
    + * to adjust DYNTICK_TASK_NESTING_VALUE accordingly.
    + *
    + * This macro may be used from process-level code only.
    + */
    +#define RCU_NONIDLE(a) \
    + do { \
    + rcu_idle_exit(); \
    + do { a; } while (0); \
    + rcu_idle_enter(); \
    + } while (0)
    +
    /*
    * Infrastructure to implement the synchronize_() primitives in
    * TREE_RCU and rcu_barrier_() primitives in TINY_RCU.
    diff --git a/kernel/rcutiny.c b/kernel/rcutiny.c
    index c8b0e15..37a5444 100644
    --- a/kernel/rcutiny.c
    +++ b/kernel/rcutiny.c
    @@ -97,6 +97,7 @@ void rcu_idle_enter(void)
    rcu_idle_enter_common(oldval);
    local_irq_restore(flags);
    }
    +EXPORT_SYMBOL_GPL(rcu_idle_enter);

    /*
    * Exit an interrupt handler towards idle.
    @@ -153,6 +154,7 @@ void rcu_idle_exit(void)
    rcu_idle_exit_common(oldval);
    local_irq_restore(flags);
    }
    +EXPORT_SYMBOL_GPL(rcu_idle_exit);

    /*
    * Enter an interrupt handler, moving away from idle.
    diff --git a/kernel/rcutree.c b/kernel/rcutree.c
    index 92b4776..eacc10b 100644
    --- a/kernel/rcutree.c
    +++ b/kernel/rcutree.c
    @@ -402,6 +402,7 @@ void rcu_idle_enter(void)
    rcu_idle_enter_common(rdtp, oldval);
    local_irq_restore(flags);
    }
    +EXPORT_SYMBOL_GPL(rcu_idle_enter);

    /**
    * rcu_irq_exit - inform RCU that current CPU is exiting irq towards idle
    @@ -493,6 +494,7 @@ void rcu_idle_exit(void)
    rcu_idle_exit_common(rdtp, oldval);
    local_irq_restore(flags);
    }
    +EXPORT_SYMBOL_GPL(rcu_idle_exit);

    /**
    * rcu_irq_enter - inform RCU that current CPU is entering irq away from idle
    --
    1.7.8


    \
     
     \ /
      Last update: 2012-02-04 02:57    [W:0.029 / U:0.792 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site