linux-toradex.git/Documentation/RCU/Design/Requirements, branch v4.10

documentation: Present updated RCU guarantee

2016-11-14T18:39:36+00:00

Recent memory-model work deduces the relationships of RCU read-side
critical sections and grace periods based on the relationships of
accesses within a critical section and accesses preceding and following
the grace period.  This commit therefore adds this viewpoint.

Signed-off-by: Paul E. McKenney

documentation: Record reason for rcu_head two-byte alignment

2016-08-22T16:25:33+00:00

There is an assertion in __call_rcu() that checks only the bottom
bit of the rcu_head pointer, rather than the bottom two (as might be
expected for 32-bit systems) or the bottom three (as might be expected
for 64-bit systems).  This choice might be a bit surprising in these days
of ubiquitous 32-bit and 64-bit systems.  This commit therefore records
the reason for this odd alignment check, namely that m68k guarantees
only two-byte alignment despite being a 32-bit architectures.

Signed-off-by: Paul E. McKenney

documentation: Add RCU_NONIDLE() restrictions to requirements

2016-06-14T23:00:59+00:00

Signed-off-by: Paul E. McKenney

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