On Thursday, September 18, 2014 05:38:45 AM Paul E. McKenney wrote: > On Thu, Sep 18, 2014 at 03:15:36PM +0800, Lan Tianyu wrote: > > 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? > > The problem with pushing for v3.17 is that I would have to rebase > that commit to the bottom of my current stack and redo all my testing. > If there were any problems, I could not only miss v3.17, but also miss > the v3.18 merge window. > > So, given that the next merge window happens pretty soon, how about > v3.18 and the stable tree?
That sounds good to me. Rafael -- 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/
