Re: [PATCH tip/core/rcu 0/13] Miscellaneous fixes for 4.4

["Paul E. McKenney" <paulmck@linux.vnet.ibm.com>]

On Tue, Oct 06, 2015 at 10:23:51AM -0700, Josh Triplett wrote:
> On Tue, Oct 06, 2015 at 09:13:05AM -0700, Paul E. McKenney wrote:
> > Hello!
> > 
> > This series contains miscellaneous fixes:
> > 
> > 1.	Export sched_setscheduler_nocheck() so that the new locktorture
> > 	rtmutex_lock tests can be run as modules, courtesy of Davidlohr
> > 	Bueso.
> > 
> > 2.	Use rcu_callback_t in call_rcu*() and friends to improve
> > 	readability and to make cscope able to find them, courtesy of
> > 	Boqun Feng.
> > 
> > 3.	Use call_rcu_func_t to replace explicit type equivalents when
> > 	defining RCU callback functions, courtesy of Boqun Feng.
> > 
> > 4.	Don't unnecessarily disable preemption for Tiny and Tree
> > 	RCU readers (only for preemptible RCU readers), courtesy
> > 	of Boqun Feng.
> > 
> > 5.	Eliminate boot-time panic when a silly boot-time fanout is
> > 	specified.
> > 
> > 6.	Add online/offline info to help debug stall-warning messages.
> > 
> > 7.	Move preemption disabling out of __srcu_read_lock() into
> > 	srcu_read_lock().
> > 
> > 8.	Finish folding ->fqs_state into ->gp_state, courtesy of Petr Mladek.
> > 
> > 9.	Correct comment for values of ->gp_state field.
> > 
> > 10.	Add rcu_pointer_handoff() to allow explicit marking of handing
> > 	off protection from RCU to some other means, such as locking
> > 	or reference counting.
> > 
> > 11.	Make list_entry_rcu() use lockless_dereference(), courtesy
> > 	of Patrick Marlier.  Despite the fact that this patch
> > 	does nothing more than eliminate a single store and a
> > 	single load of an unshared stack variable it nevertheless
> > 	manages to provide a measurable performance increase:
> > 	http://people.csail.mit.edu/amatveev/RLU_SOSP2015.pdf
> > 
> > 12.	Remove deprecated rcu_lockdep_assert().
> 
> (And a patch 13 not mentioned here.)

Oops...  "Use WRITE_ONCE() when deleting from reader-visible list" included
to make KTSAN happier.

> I responded to patches 4, 6, and 10 with feedback; for the rest (and for
> those with the issues addressed):
> 
> Reviewed-by: Josh Triplett <josh@joshtriplett.org>

Thank you for the review and comments!

							Thanx, Paul