linux.git/Documentation/RCU, branch v4.15

Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2017-11-13T20:18:10+00:00

Pull RCU updates from Ingo Molnar:
 "The main changes in this cycle are:

   - Documentation updates

   - RCU CPU stall-warning updates

   - Torture-test updates

   - Miscellaneous fixes

  Size wise the biggest updates are to documentation. Excluding
  documentation most of the code increase comes from a single commit
  which expands debugging"

* 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (24 commits)
  srcu: Add parameters to SRCU docbook comments
  doc: Rewrite confusing statement about memory barriers
  memory-barriers.txt: Fix typo in pairing example
  rcu/segcblist: Include rcupdate.h
  rcu: Add extended-quiescent-state testing advice
  rcu: Suppress lockdep false-positive ->boost_mtx complaints
  rcu: Do not include rtmutex_common.h unconditionally
  torture: Provide TMPDIR environment variable to specify tmpdir
  rcutorture: Dump writer stack if stalled
  rcutorture: Add interrupt-disable capability to stall-warning tests
  rcu: Suppress RCU CPU stall warnings while dumping trace
  rcu: Turn off tracing before dumping trace
  rcu: Make RCU CPU stall warnings check for irq-disabled CPUs
  sched,rcu: Make cond_resched() provide RCU quiescent state
  sched: Make resched_cpu() unconditional
  irq_work: Map irq_work_on_queue() to irq_work_on() in !SMP
  rcu: Create call_rcu_tasks() kthread at boot time
  rcu: Fix up pending cbs check in rcu_prepare_for_idle
  memory-barriers: Rework multicopy-atomicity section
  memory-barriers: Replace uses of "transitive"
  ...

Documentation: fix ref to workqueue content

2017-10-19T18:57:26+00:00

Signed-off-by: Tom Saeger 
Signed-off-by: Jonathan Corbet

documentation: Update RCU CPU stall warning messages

2017-10-09T21:23:36+00:00

The RCU CPU stall warnings have morphed significantly since the last
update, so this commit brings the documentation up to date.

Signed-off-by: Paul E. McKenney

documentation: Slow systems can stall RCU grace periods

2017-10-09T21:23:36+00:00

If a fast system has a worst-case grace-period duration of (say) ten
seconds, then running the same workload on a system ten times as slow
will get you an RCU CPU stall warning given default stall-warning
timeout settings.  This commit therefore adds this possibility to
stallwarn.txt.

Reported-by: Daniel Lezcano 
Signed-off-by: Paul E. McKenney

documentation: Long-running irq handlers can stall RCU grace periods

2017-10-09T21:23:36+00:00

If a periodic interrupt's handler takes longer to execute than the period
between successive interrupts, RCU's kthreads and softirq handlers can
be prevented from executing, resulting in otherwise inexplicable RCU
CPU stall warnings.  This commit therefore calls out this possibility
in Documentation/RCU/stallwarn.txt.

Reported-by: Daniel Lezcano 
Signed-off-by: Paul E. McKenney

documentation: RCU grace-period memory ordering guarantees

2017-10-09T21:23:36+00:00

This commit provides text and diagrams showing how Tree RCU implements
its grace-period memory ordering guarantees.

Signed-off-by: Paul E. McKenney 
Cc: Jonathan Corbet 
Cc: Linus Torvalds

doc: Set down RCU's scheduling-clock-interrupt needs

2017-08-17T14:31:14+00:00

This commit documents the situations in which RCU needs the
scheduling-clock interrupt to be enabled, along with the consequences
of failing to meet RCU's needs in this area.

Signed-off-by: Paul E. McKenney

doc: No longer allowed to use rcu_dereference on non-pointers

2017-08-17T14:29:58+00:00

There are too many ways for the compiler to optimize (that is, break)
dependencies carried via integer values, so it is now permissible to
carry dependencies only via pointers.  This commit catches up some of
the documentation on this point.

Signed-off-by: Paul E. McKenney

doc: Update RCU documentation

2017-08-17T14:29:48+00:00

Signed-off-by: Paul E. McKenney

rcu: Remove debugfs tracing

2017-06-09T01:52:43+00:00

RCU's debugfs tracing used to be the only reasonable low-level debug
information available, but ftrace and event tracing has since surpassed
the RCU debugfs level of usefulness.  This commit therefore removes
RCU's debugfs tracing.

Signed-off-by: Paul E. McKenney