linux-stable.git/Documentation/RCU/Design/Requirements, branch linux-4.7.y

documentation: Emphasize the call_rcu() is illegal from idle

2016-03-31T20:33:23+00:00

Although call_rcu()'s fastpath works just fine on an idle CPU,
some branches of the slowpath invoke the scheduler, which uses
RCU.  Therefore, this commit emphasizes the fact that call_rcu()
must not be invoked from an idle CPU.

Signed-off-by: Paul E. McKenney

documentation: Sharpen up the no-readers quick quiz

2016-03-31T20:33:23+00:00

Signed-off-by: Paul E. McKenney

documentation: Get rid of duplicate .htmlx file

2016-03-31T20:33:22+00:00

This commit uses colors to obscure the quick-quiz answers, thus getting
rid of the .htmlx file.  Use your mouse to select the answer in order
to see the text.  Alternatively, use your favorite scripting language
to remove all occurences of "" from the file.

Reported-by: Linus Torvalds 
Signed-off-by: Paul E. McKenney

documentation: Remove unnecessary images from requirements

2016-03-31T20:33:21+00:00

This commit removes a cutesy cartoon and also a diagram that can
just as easily be represented by text.

Reported-by: Linus Torvalds 
Signed-off-by: Paul E. McKenney

documentation: Document illegality of call_rcu() from offline CPUs

2016-03-31T20:33:21+00:00

There is already a blanket statement about no member of RCU's API
being legal from an offline CPU, but add an explicit note where it
states that it is illegal to invoke call_rcu() from an NMI handler.

Signed-off-by: Paul E. McKenney

documentation: Explain why rcu_read_lock() needs no barrier()

2016-03-31T20:33:20+00:00

This commit adds a Quick Quiz whose answer explains why the compiler
code reordering enabled by CONFIG_PREEMPT=n's empty rcu_read_lock()
and rcu_read_unlock() functions does not hinder RCU's ability to figure
out which RCU read-side critical sections have completed and not.

Signed-off-by: Paul E. McKenney

documentation: Add synchronize_rcu_mult() to the requirements

2016-03-31T20:33:20+00:00

Signed-off-by: Paul E. McKenney

documentation: Add real-time requirements from CPU-bound workloads

2016-03-31T20:33:19+00:00

This commit records RCU's responsibility to avoid degrading latencies
of CPUs running tight loops within properly configured workloads,
both in kernel and in userspace.

Signed-off-by: Paul E. McKenney

documentation: Update RCU requirements based on expedited changes

2015-12-05T20:34:32+00:00

Because RCU-sched expedited grace periods now use IPIs and interact
with rcu_read_unlock(), it is no longer sufficient to disable preemption
across RCU read-side critical sections that acquire and hold scheduler
locks.  It is now necessary to instead disable interrupts.  This commit
documents this change.

Signed-off-by: Paul E. McKenney

documentation: Clarify RCU memory barriers and requirements

2015-12-05T20:33:37+00:00

The RCU requirements do not make it absolutely clear that the
memory-barrier requirements are not intended to replace the fundamental
requirement that all pre-existing RCU readers complete before a grace
period completes.  This commit therefore pulls the memory-barrier
requirements into a separate section and explicitly calls out the
relationship between the memory-barrier requirements and the fundamental
requirement.

Signed-off-by: Paul E. McKenney