linux-kernel - [PATCH tip/core/rcu 0/17] RCU dyntick updates for v4.16

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Date:   Fri, 1 Dec 2017 11:36:25 -0800
From:   "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:     linux-kernel@...r.kernel.org
Cc:     mingo@...nel.org, jiangshanlai@...il.com, dipankar@...ibm.com,
        akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
        josh@...htriplett.org, tglx@...utronix.de, peterz@...radead.org,
        rostedt@...dmis.org, dhowells@...hat.com, edumazet@...gle.com,
        fweisbec@...il.com, oleg@...hat.com
Subject: [PATCH tip/core/rcu 0/17] RCU dyntick updates for v4.16

Hello!

This series includes simplifications of RCU's dyntick-idle processing,
most importantly making use of the the NMI style of processing for
interrupts as well as NMIs.  This series provides a net decrease of more
than 100 lines of code.

1.	Avoid ->dynticks_nmi_nesting store tearing.

2.	Reduce dyntick-idle state space by carefully ordering adjustments
	of nesting and overall state.

3.	Move rcu_nmi_{enter,exit}() to prepare for consolidation.

4.	Clamp ->dynticks_nmi_nesting at eqs entry/exit.  This is required
	to handle the half-interrupts featured by some architectures.
	It used to be handled by the interrupt portion of RCU's
	dyntick-idle processing, which this series is eliminating.
	Thus the clamping must move.

5.	Define rcu_irq_{enter,exit}() in terms of rcu_nmi_{enter,exit}().

6.	Make ->dynticks_nesting be a simple counter, given that it now
	handles only process-level reasons why RCU should be watching.

7.	Eliminate rcu_irq_enter_disabled() because the NMI handling
	already handles the possibility of interruption at any point.

8.	Add tracing to irq/NMI dyntick-idle transitions.

9.	Shrink ->dynticks_{nmi_,}nesting from long long to long because
	there had better not be more than a billion process-level reasons
	why RCU should be watching a given CPU.

10.	Add ->dynticks field to rcu_dyntick trace event.

11.	Stop duplicating lockdep checks in RCU's idle-entry code.

12.	Avoid ->dynticks_nesting store tearing.

13.	Fold rcu_eqs_enter_common() into rcu_eqs_enter() because it is
	now only invoked from that one place.

14.	Fold rcu_eqs_exit_common() into rcu_eqs_exit() because it is now
	only invoked from that one place.

15.	Simplify rcu_eqs_{enter,exit}() non-idle task debug code.

16.	Update dyntick-idle design documentation to reflect NMI/irq
	consolidation.

17.	Remove no longer used trace event rcu_prep_idle, courtesy of
	Steven Rostedt.

								Thanx, Paul

------------------------------------------------------------------------

 Documentation/RCU/Design/Data-Structures/Data-Structures.html |   46 
 include/linux/rcutiny.h                                       |    1 
 include/linux/rcutree.h                                       |    1 
 include/linux/tracepoint.h                                    |    5 
 include/trace/events/rcu.h                                    |   87 -
 kernel/rcu/rcu.h                                              |   31 
 kernel/rcu/tree.c                                             |  466 ++++------
 kernel/rcu/tree.h                                             |    5 
 kernel/rcu/tree_plugin.h                                      |    2 
 kernel/trace/trace.c                                          |   11 
 10 files changed, 256 insertions(+), 399 deletions(-)