On 2014年08月29日 03:47, Paul E. McKenney wrote:
> Currently, the expedited grace-period primitives do get_online_cpus().
> This greatly simplifies their implementation, but means that calls to
> them holding locks that are acquired by CPU-hotplug notifiers (to say
> nothing of calls to these primitives from CPU-hotplug notifiers) can
> deadlock. But this is starting to become inconvenient:
> https://lkml.org/lkml/2014/8/5/754
>
> This commit avoids the deadlock and retains the simplicity by creating
> a try_get_online_cpus(), which returns false if the get_online_cpus()
> reference count could not immediately be incremented. If a call to
> try_get_online_cpus() returns true, the expedited primitives operate
> as before. If a call returns false, the expedited primitives fall back
> to normal grace-period operations. This falling back of course results
> in increased grace-period latency, but only during times when CPU
> hotplug operations are actually in flight. The effect should therefore
> be negligible during normal operation.
>
> Signed-off-by: Paul E. McKenney <[email protected]>
> Cc: Josh Triplett <[email protected]>
> Cc: "Rafael J. Wysocki" <[email protected]>
> Cc: Lan Tianyu <[email protected]>
Hi Paul:
What's the status of the patch? Will you push it? Thanks.
--
Best regards
Tianyu Lan
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