On 2014年09月17日 21:10, Paul E. McKenney wrote: > 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 <paul...@linux.vnet.ibm.com> >>> Cc: Josh Triplett <j...@joshtriplett.org> >>> Cc: "Rafael J. Wysocki" <r...@rjwysocki.net> >>> Cc: Lan Tianyu <tianyu....@intel.com> >> >> 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?
IMO, this is a dead lock bug which is hard to reproduce and the patch should go into v3.17 and stable tree? > > Thanx, Paul > -- Best regards Tianyu Lan -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
