linux-kernel - Re: [PATCH tip/core/rcu 0/55] Preview of RCU changes for 3.2

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Message-ID: <20111017020613.GJ19421@leaf>
Date:	Sun, 16 Oct 2011 19:06:13 -0700
From:	Josh Triplett <josh@...htriplett.org>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:	linux-kernel@...r.kernel.org, mingo@...e.hu, laijs@...fujitsu.com,
	dipankar@...ibm.com, akpm@...ux-foundation.org,
	mathieu.desnoyers@...ymtl.ca, niv@...ibm.com, tglx@...utronix.de,
	peterz@...radead.org, rostedt@...dmis.org, Valdis.Kletnieks@...edu,
	dhowells@...hat.com, eric.dumazet@...il.com, darren@...art.com,
	patches@...aro.org
Subject: Re: [PATCH tip/core/rcu 0/55] Preview of RCU changes for 3.2

On Tue, Sep 06, 2011 at 11:00:15AM -0700, Paul E. McKenney wrote:
> Hello!
> 
> This patchset adds RCU event tracing, improved diagnostics and
> documentation, and fixes a number of bugs, including several from an
> ongoing top-to-bottom inspection of RCU.  The patches are as follows:
> 
> 1.	Place per-CPU kthreads' stack and task struct on the corresponding
> 	node on NUMA systems (courtesy of Eric Dumazet).
> 2.	Avoid unnecessary self-wakeups for per-CPU kthreads
> 	(courtesy of Shaohua Li).
> 3,6,10,12,25,28,33.
> 	Documentations updates (some courtesy Wanlong Gao).
> 4.	Add replacement checks for blocking within an RCU read-side
> 	critical section.
> 5.	Header-file untangling part 1 of N: move rcu_head to types.h.
> 7.	Fix mismatched variable declaration (courtesy of Andi Kleen).
> 8.	Abstract out common grace-period-primitive code.
> 9.	Update rcutorture to test newish RCU API members.
> 11.	Drive RCU algorithm selection directly from SMP and PREEMPT.
> 13.	Make rcu_torture_boost() wait for callbacks before telling
> 	debug-objects that they are done.
> 14-17,20,22.
> 	Add event tracing for RCU.
> 18.	Update comments to reflect kthreads being used only when
> 	RCU priority boosting is enabled.
> 19.	Move RCU_BOOSt data declarations to alow compiler to detect
> 	mismatches.
> 20.	Make TINY_RCU use softirqs for RCU_BOOST=n.
> 23.	Simplify quiescent-state accounting.
> 24.	Stop passing rcu_read_lock_held() to rcu_dereference_protected()
> 	(courtesy of Michal Hocko).
> 26.	Remove unused and redundant RCU API members.
> 27.	Allow rcutorture's stat_interval parameter to be changed at runtime
> 	to make it easier to test RCU in guest OSes.
> 28.	Removed unused nohz_cpu_mask (courtesy of Alex Shi).
> 30.	Eliminate in_irq() checks in rcu_enter_nohz().
> 31.	Fix rcu_implicit_dynticks_qs() local-variable size mismatches.
> 32.	Make rcu_assign_pointer() unconditionally emit memory barrier
> 	to silence new gcc warnings (courtesy of Eric Dumazet).
> 34.	Move __rcu_read_lock()'s barrier within if-statement.
> 35.	Dump local stack for CPU stall warnings if cannot dump all stacks.
> 36.	Prevent early-boot set_need_resched() from __rcu_pending().
> 37.	Simplify unboosting checks.
> 38.	Prohibit RCU grace periods during early boot.
> 39.	Suppress NMI backtraces when CPU stall ends before dump.
> 40.	Avoid just-online CPU needlessly rescheding itself.
> 41.	Permit rt_mutex_unlock() with irqs disabled.
> 42-43.	Prevent end-of-test rcutorture hangs.
> 44.	Wire up RCU_BOOST_PRIO, use conventional kthread naming scheme
> 	(courtesy of Mike Galbraith).
> 45.	Check for entering dyntick-idle in RCU read-side critical section.
> 46.	Adjust RCU_FAST_NO_HZ to avoid false quiescent states.
> 47.	Avoid concurrent end of old GP with start of new GP.
> 48.	Strengthen powerpc value-returning atomic memory ordering.
> 49-51.	Detect illegal RCU use from dyntick-idle mode (courtesy of
> 	Frederic Weisbecker).
> 52.	Remove an unnecessary layer of abstraction from PROVE_RCU checking.
> 53.	Detect illegal SRCU use from dyntick-idle mode.
> 54.	Make SRCU use common lockdep-splat code.
> 55.	Placeholder patch that disables illegal tracing from dyntick-idle
> 	mode (illegal because tracing uses RCU).

I responded to a few of the patches with comments and potential issues.
I also don't consider myself qualified to review patch 48/55, "powerpc:
strengthen value-returning-atomics memory barriers".  For the rest:

Reviewed-by: Josh Triplett <josh@...htriplett.org>
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