linux-toradex.git/include/linux/rcutiny.h, branch v4.3-rc3

rcu: Add RCU-sched flavors of get-state and cond-sync

2015-07-22T22:26:58+00:00

The get_state_synchronize_rcu() and cond_synchronize_rcu() functions
allow polling for grace-period completion, with an actual wait for a
grace period occurring only when cond_synchronize_rcu() is called too
soon after the corresponding get_state_synchronize_rcu().  However,
these functions work only for vanilla RCU.  This commit adds the
get_state_synchronize_sched() and cond_synchronize_sched(), which provide
the same capability for RCU-sched.

Reported-by: Peter Zijlstra (Intel) 
Signed-off-by: Paul E. McKenney

rcu: Further shrink Tiny RCU by making empty functions static inlines

2015-05-27T19:59:31+00:00

The Tiny RCU counterparts to rcu_idle_enter(), rcu_idle_exit(),
rcu_irq_enter(), and rcu_irq_exit() are empty functions, but each has
EXPORT_SYMBOL_GPL(), which needlessly consumes extra memory, especially
in kernels built with module support.  This commit therefore moves these
functions to static inlines in rcutiny.h, removing the need for exports.

This won't affect the size of the tiniest kernels, which are likely
built without module support, but might help semi-tiny kernels that
might include module support.

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

Merge branches 'doc.2015.01.07a', 'fixes.2015.01.15a', 'preempt.2015.01.06a', 'srcu.2015.01.06a', 'stall.2015.01.16a' and 'torture.2015.01.11a' into HEAD

2015-01-16T07:34:34+00:00

doc.2015.01.07a: Documentation updates.
fixes.2015.01.15a: Miscellaneous fixes.
preempt.2015.01.06a: Changes to handling of lists of preempted tasks.
srcu.2015.01.06a: SRCU updates.
stall.2015.01.16a: RCU CPU stall-warning updates and fixes.
torture.2015.01.11a: RCU torture-test updates and fixes.

rcu: Make cond_resched_rcu_qs() apply to normal RCU flavors

2015-01-16T07:33:14+00:00

Although cond_resched_rcu_qs() only applies to TASKS_RCU, it is used
in places where it would be useful for it to apply to the normal RCU
flavors, rcu_preempt, rcu_sched, and rcu_bh.  This is especially the
case for workloads that aggressively overload the system, particularly
those that generate large numbers of RCU updates on systems running
NO_HZ_FULL CPUs.  This commit therefore communicates quiescent states
from cond_resched_rcu_qs() to the normal RCU flavors.

Note that it is unfortunately necessary to leave the old ->passed_quiesce
mechanism in place to allow quiescent states that apply to only one
flavor to be recorded.  (Yes, we could decrement ->rcu_qs_ctr_snap in
that case, but that is not so good for debugging of RCU internals.)
In addition, if one of the RCU flavor's grace period has stalled, this
will invoke rcu_momentary_dyntick_idle(), resulting in a heavy-weight
quiescent state visible from other CPUs.

Reported-by: Sasha Levin 
Reported-by: Dave Jones 
Signed-off-by: Paul E. McKenney 
[ paulmck: Merge commit from Sasha Levin fixing a bug where __this_cpu()
  was used in preemptible code. ]

rcutorture: Check from beginning to end of grace period

2015-01-11T03:08:02+00:00

Currently, rcutorture's Reader Batch checks measure from the end of
the previous grace period to the end of the current one.  This commit
tightens up these checks by measuring from the start and end of the same
grace period.  This involves adding rcu_batches_started() and friends
corresponding to the existing rcu_batches_completed() and friends.

We leave SRCU alone for the moment, as it does not yet have a way of
tracking both ends of its grace periods.

Signed-off-by: Paul E. McKenney

rcu: Provide rcu_batches_completed_sched() for TINY_RCU

2015-01-11T03:07:59+00:00

A bug in rcutorture has caused it to ignore completed batches.
In preparation for fixing that bug, this commit provides TINY_RCU with
the required rcu_batches_completed_sched().

Signed-off-by: Paul E. McKenney

rcu: Make _batches_completed() functions return unsigned long

2015-01-11T03:07:56+00:00

Long ago, the various ->completed fields were of type long, but now are
unsigned long due to signed-integer-overflow concerns.  However, the
various _batches_completed() functions remained of type long, even though
their only purpose in life is to return the corresponding ->completed
field.  This patch cleans this up by changing these functions' return
types to unsigned long.

Signed-off-by: Paul E. McKenney

rcu: Remove "cpu" argument to rcu_note_context_switch()

2014-11-04T03:20:34+00:00

The "cpu" argument to rcu_note_context_switch() is always the current
CPU, so drop it.  This in turn allows the "cpu" argument to
rcu_preempt_note_context_switch() to be removed, which allows the sole
use of "cpu" in both functions to be replaced with a this_cpu_ptr().
Again, the anticipated cross-CPU uses of these functions has been
replaced by NO_HZ_FULL.

Signed-off-by: Paul E. McKenney 
Reviewed-by: Pranith Kumar

rcu: Per-CPU operation cleanups to rcu_*_qs() functions

2014-09-07T23:27:35+00:00

The rcu_bh_qs(), rcu_preempt_qs(), and rcu_sched_qs() functions use
old-style per-CPU variable access and write to ->passed_quiesce even
if it is already set.  This commit therefore updates to use the new-style
per-CPU variable access functions and avoids the spurious writes.
This commit also eliminates the "cpu" argument to these functions because
they are always invoked on the indicated CPU.

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

rcutorture: Export RCU grace-period kthread wait state to rcutorture

2014-05-14T16:46:09+00:00

This commit allows rcutorture to print additional state for the
RCU grace-period kthreads in cases where RCU seems reluctant to
start a new grace period.

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