linux-toradex.git/kernel/rcu, branch v4.4-rc6

Merge branches 'doc.2015.10.06a', 'percpu-rwsem.2015.10.06a' and 'torture.2015.10.06a' into HEAD

2015-10-07T23:06:25+00:00

doc.2015.10.06a:  Documentation updates.
percpu-rwsem.2015.10.06a:  Optimization of per-CPU reader-writer semaphores.
torture.2015.10.06a:  Torture-test updates.

Merge branches 'fixes.2015.10.06a' and 'exp.2015.10.07a' into HEAD

2015-10-07T23:05:21+00:00

exp.2015.10.07a:  Reduce OS jitter of RCU-sched expedited grace periods.
fixes.2015.10.06a:  Miscellaneous fixes.

rcu: Better hotplug handling for synchronize_sched_expedited()

2015-10-07T23:02:50+00:00

Earlier versions of synchronize_sched_expedited() can prematurely end
grace periods due to the fact that a CPU marked as cpu_is_offline()
can still be using RCU read-side critical sections during the time that
CPU makes its last pass through the scheduler and into the idle loop
and during the time that a given CPU is in the process of coming online.
This commit therefore eliminates this window by adding additional
interaction with the CPU-hotplug operations.

Signed-off-by: Paul E. McKenney

rcu: Enable stall warnings for synchronize_rcu_expedited()

2015-10-07T23:02:50+00:00

This commit redirects synchronize_rcu_expedited()'s wait to
synchronize_sched_expedited_wait(), thus enabling RCU CPU
stall warnings.

Signed-off-by: Paul E. McKenney

rcu: Add tasks to expedited stall-warning messages

2015-10-07T23:02:50+00:00

This commit adds task-print ability to the expedited RCU CPU stall
warning messages in preparation for adding stall warnings to
synchornize_rcu_expedited().

Signed-off-by: Paul E. McKenney

rcu: Add online/offline info to expedited stall warning message

2015-10-07T23:02:50+00:00

This commit makes the RCU CPU stall warning message print online/offline
indications immediately after the CPU number.  A "O" indicates global
offline, a "." global online, and a "o" indicates RCU believes that the
CPU is offline for the current grace period and "." otherwise, and an
"N" indicates that RCU believes that the CPU will be offline for the
next grace period, and "." otherwise, all right after the CPU number.
So for CPU 10, you would normally see "10-...:" indicating that everything
believes that the CPU is online.

Signed-off-by: Paul E. McKenney

rcu: Consolidate expedited CPU selection

2015-10-07T23:02:50+00:00

Now that sync_sched_exp_select_cpus() and sync_rcu_exp_select_cpus()
are identical aside from the the argument to smp_call_function_single(),
this commit consolidates them with a functional argument.

Signed-off-by: Paul E. McKenney

rcu: Prepare for consolidating expedited CPU selection

2015-10-07T23:02:50+00:00

This commit brings sync_sched_exp_select_cpus() into alignment with
sync_rcu_exp_select_cpus(), as a first step towards consolidating them
into one function.

Signed-off-by: Paul E. McKenney

rcu: Stop excluding CPU hotplug in synchronize_sched_expedited()

2015-10-07T23:02:49+00:00

Now that synchronize_sched_expedited() uses IPIs, a hook in
rcu_sched_qs(), and the ->expmask field in the rcu_node combining
tree, it is no longer necessary to exclude CPU hotplug.  Any
races with CPU hotplug will be detected when attempting to send
the IPI.  This commit therefore removes the code excluding
CPU hotplug operations.

Signed-off-by: Paul E. McKenney

rcu: Stop silencing lockdep false positive for expedited grace periods

2015-10-07T23:02:49+00:00

This reverts commit af859beaaba4 (rcu: Silence lockdep false positive
for expedited grace periods).  Because synchronize_rcu_expedited()
no longer invokes synchronize_sched_expedited(), ->exp_funnel_mutex
acquisition is no longer nested, so the false positive no longer happens.
This commit therefore removes the extra lockdep data structures, as they
are no longer needed.