linux-toradex.git/include/linux/rcutiny.h, branch v4.13-rc4

rcu: Remove #ifdef moving rcu_end_inkernel_boot from rcupdate.h

2017-06-09T01:52:40+00:00

This commit removes a #ifdef and saves a few lines of code by moving
the rcu_end_inkernel_boot() function from include/linux/rcupdate.h to
include/linux/rcutiny.h (for TINY_RCU) and to include/linux/rcutree.h
(for TREE_RCU).

Signed-off-by: Paul E. McKenney

rcu: Refactor #includes from include/linux/rcupdate.h

2017-06-09T01:52:37+00:00

The list of #includes from include/linux/rcupdate.h has grown quite
a bit, so it is time to trim it.  This commit moves the #include
of include/linux/ktime.h to include/linux/rcutiny.h, along with the
Tiny-RCU-only function that was the only thing needing ktimem.h.  It then
reconstructs the files included into include/linux/ktime.h based on what
is actually needed, with significant help from the 0day Test Robot.

This single change reduces the .i file footprint from rcupdate.h from
9018 lines to 7101 lines.

Reported-by: Ingo Molnar 
Signed-off-by: Paul E. McKenney

rcu: Move rcutiny.h to new empty/true/false-function style

2017-06-09T01:52:34+00:00

This commit saves a few lines in include/linux/rcutiny.h by moving
to single-line definitions for empty functions, instead of the old
style where the two curly braces each get their own line.

Reported-by: Ingo Molnar 
Signed-off-by: Paul E. McKenney

rcu: Move rcu_request_urgent_qs_task() out of rcutiny.h and rcutree.h

2017-06-09T01:52:33+00:00

The rcu_request_urgent_qs_task() function is used only within RCU,
so there is no point in exporting it to the rest of the kernel from
nclude/linux/rcutiny.h and include/linux/rcutree.h.  This commit therefore
moves this function to kernel/rcu/rcu.h.

Reported-by: Ingo Molnar 
Signed-off-by: Paul E. McKenney

rcu: Move torture-related functions out of rcutiny.h and rcutree.h

2017-06-09T01:52:33+00:00

The various functions similar to rcu_batches_started(), the
function show_rcu_gp_kthreads(), the various functions similar to
rcu_force_quiescent_state(), and the variables rcutorture_testseq and
rcutorture_vernum are used only within RCU.  There is therefore no point
in exporting them to the kernel at large from include/linux/rcutiny.h
and include/linux/rcutree.h.  This commit therefore moves all of these
to kernel/rcu/rcu.h.

Reported-by: Ingo Molnar 
Signed-off-by: Paul E. McKenney

rcu: Eliminate the unused __rcu_is_watching() function

2017-06-09T01:52:30+00:00

The __rcu_is_watching() function is currently not used, aside from
to implement the rcu_is_watching() function.  This commit therefore
eliminates __rcu_is_watching(), which has the beneficial side-effect
of shrinking include/linux/rcupdate.h a bit.

Reported-by: Ingo Molnar 
Signed-off-by: Paul E. McKenney

rcu: Move torture-related definitions from rcupdate.h to rcu.h

2017-06-09T01:52:28+00:00

The include/linux/rcupdate.h file contains a number of definitions that
are used only to communicate between rcutorture, rcuperf, and the RCU code
itself.  There is no point in having these definitions exposed globally
throughout the kernel, so this commit moves them to kernel/rcu/rcu.h.
This change has the added benefit of shrinking rcupdate.h.

Reported-by: Ingo Molnar 
Signed-off-by: Paul E. McKenney

rcu: Make non-preemptive schedule be Tasks RCU quiescent state

2017-04-21T12:59:27+00:00

Currently, a call to schedule() acts as a Tasks RCU quiescent state
only if a context switch actually takes place.  However, just the
call to schedule() guarantees that the calling task has moved off of
whatever tracing trampoline that it might have been one previously.
This commit therefore plumbs schedule()'s "preempt" parameter into
rcu_note_context_switch(), which then records the Tasks RCU quiescent
state, but only if this call to schedule() was -not- due to a preemption.

To avoid adding overhead to the common-case context-switch path,
this commit hides the rcu_note_context_switch() check under an existing
non-common-case check.

Suggested-by: Steven Rostedt 
Signed-off-by: Paul E. McKenney

srcu: Allow SRCU to access rcu_scheduler_active

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

This is primarily a code-movement commit in preparation for allowing
SRCU to handle early-boot SRCU grace periods.

Signed-off-by: Paul E. McKenney

rcu: Maintain special bits at bottom of ->dynticks counter

2017-04-18T18:19:22+00:00

Currently, IPIs are used to force other CPUs to invalidate their TLBs
in response to a kernel virtual-memory mapping change.  This works, but
degrades both battery lifetime (for idle CPUs) and real-time response
(for nohz_full CPUs), and in addition results in unnecessary IPIs due to
the fact that CPUs executing in usermode are unaffected by stale kernel
mappings.  It would be better to cause a CPU executing in usermode to
wait until it is entering kernel mode to do the flush, first to avoid
interrupting usemode tasks and second to handle multiple flush requests
with a single flush in the case of a long-running user task.

This commit therefore reserves a bit at the bottom of the ->dynticks
counter, which is checked upon exit from extended quiescent states.
If it is set, it is cleared and then a new rcu_eqs_special_exit() macro is
invoked, which, if not supplied, is an empty single-pass do-while loop.
If this bottom bit is set on -entry- to an extended quiescent state,
then a WARN_ON_ONCE() triggers.

This bottom bit may be set using a new rcu_eqs_special_set() function,
which returns true if the bit was set, or false if the CPU turned
out to not be in an extended quiescent state.  Please note that this
function refuses to set the bit for a non-nohz_full CPU when that CPU
is executing in usermode because usermode execution is tracked by RCU
as a dyntick-idle extended quiescent state only for nohz_full CPUs.

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