On Wed, Sep 17, 2014 at 03:11:42PM +0800, Lan Tianyu wrote:
> 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.
By default, it would go into 3.19. Do you need it earlier?
Thanx, Paul
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
