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    SubjectRe: [PATCH] rcu: Is it safe to enter an RCU read-side critical section?
    * Paul E. McKenney (paulmck@linux.vnet.ibm.com) wrote:
    > On Mon, Sep 09, 2013 at 12:34:22PM -0400, Steven Rostedt wrote:
    [...]
    > > "rcu_is_ignored()" or "rcu_is_not_active()", "rcu_is_watching_you()"
    >
    > You know, I am strongly tempted by "rcu_is_watching_you()", but I have
    > this feeling that it is too cute for its own good. ;-)

    Wow, I just got off the plane, and look at what happened to this thread
    ;-)

    Referring to your earlier question Paul, what I meant by my earlier
    email on naming has been addressed by Steven: when exposing a new RCU
    API, even if it is just for in-kernel use, we should be really cautious
    not to tie it to implementation, but rather to concepts. Basically, my
    original thought is that we should be able to express the exact same
    concept in the kernel RCU implementation and in Userspace RCU. Here,
    binding the name on whether the CPU is watching RCU really makes no
    sense for urcu, since all the RCU flavors we currently have are watching
    threads, not CPUs.

    Hence my proposal for "rcu_read_check()". It could be "rcu_is_active()"
    too, I don't really mind. It really minds: Is RCU actively watching the
    current execution context ? This can be translated to a runtime check
    too: is it safe to call rcu_read_lock() form this context ?

    Thanks,

    Mathieu


    --
    Mathieu Desnoyers
    EfficiOS Inc.
    http://www.efficios.com


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