linux.git/Documentation/RCU/Design/Data-Structures/Data-Structures.html, branch v4.14

Merge branches 'doc.2017.04.12a', 'fixes.2017.04.19a' and 'srcu.2017.04.21a' into HEAD

2017-04-21T13:00:13+00:00

doc.2017.04.12a: Documentation updates
fixes.2017.04.19a: Miscellaneous fixes
srcu.2017.04.21a: Parallelize SRCU callback handling

rcu: Place guard on rcu_all_qs() and rcu_note_context_switch() actions

2017-04-18T18:38:18+00:00

The rcu_all_qs() and rcu_note_context_switch() do a series of checks,
taking various actions to supply RCU with quiescent states, depending
on the outcomes of the various checks.  This is a bit much for scheduling
fastpaths, so this commit creates a separate ->rcu_urgent_qs field in
the rcu_dynticks structure that acts as a global guard for these checks.
Thus, in the common case, rcu_all_qs() and rcu_note_context_switch()
check the ->rcu_urgent_qs field, find it false, and simply return.

Signed-off-by: Paul E. McKenney 
Cc: Peter Zijlstra

rcu: Eliminate flavor scan in rcu_momentary_dyntick_idle()

2017-04-18T18:38:18+00:00

The rcu_momentary_dyntick_idle() function scans the RCU flavors, checking
that one of them still needs a quiescent state before doing an expensive
atomic operation on the ->dynticks counter.  However, this check reduces
overhead only after a rare race condition, and increases complexity.  This
commit therefore removes the scan and the mechanism enabling the scan.

Signed-off-by: Paul E. McKenney

rcu: Pull rcu_qs_ctr into rcu_dynticks structure

2017-04-18T18:38:17+00:00

The rcu_qs_ctr variable is yet another isolated per-CPU variable,
so this commit pulls it into the pre-existing rcu_dynticks per-CPU
structure.

Signed-off-by: Paul E. McKenney

rcu: Pull rcu_sched_qs_mask into rcu_dynticks structure

2017-04-18T18:38:17+00:00

The rcu_sched_qs_mask variable is yet another isolated per-CPU variable,
so this commit pulls it into the pre-existing rcu_dynticks per-CPU
structure.

Signed-off-by: Paul E. McKenney

doc: Update RCU data-structure documentation for rcu_segcblist

2017-04-12T15:23:41+00:00

The rcu_segcblist data structure, which contains segmented lists
of RCU callbacks, was recently added.  This commit updates the
documentation accordingly.

Signed-off-by: Paul E. McKenney

doc: Quick-Quiz answers are now inline

2017-01-15T05:30:33+00:00

Now that quick-quiz answers are inline, there is no separate section
containing those answers.  This commit therefore removes the dangling
reference from the RCU data-structures design documentation.

Signed-off-by: Paul E. McKenney 
Reviewed-by: Josh Triplett

documentation: Add documentation for RCU's major data structures

2016-04-19T21:48:12+00:00

This commit adds documentation for RCU's major data structures,
including rcu_state, rcu_node, rcu_data, rcu_dynticks, and rcu_head.

Signed-off-by: Paul E. McKenney