linux-stable.git/kernel/rcu/tree.c, branch v4.5

Merge branches 'doc.2015.12.05a', 'exp.2015.12.07a', 'fixes.2015.12.07a', 'list.2015.12.04b' and 'torture.2015.12.05a' into HEAD

2015-12-08T01:02:54+00:00

doc.2015.12.05a:  Documentation updates
exp.2015.12.07a:  Expedited grace-period updates
fixes.2015.12.07a:  Miscellaneous fixes
list.2015.12.04b:  Linked-list updates
torture.2015.12.05a:  Torture-test updates

rcu: Make rcu_gp_init() be bool rather than int

2015-12-08T01:01:33+00:00

The return value from rcu_gp_init() is always used as a bool, so
this commit makes it be a bool.

Reported-by: Iftekhar Ahmed 
Signed-off-by: Paul E. McKenney

rcu: Move wakeup out from under rnp->lock

2015-12-08T01:01:32+00:00

This patch removes a potential deadlock hazard by moving the
wake_up_process() in rcu_spawn_gp_kthread() out from under rnp->lock.

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

rcu: Don't redundantly disable irqs in rcu_irq_{enter,exit}()

2015-12-08T01:01:31+00:00

This commit replaces a local_irq_save()/local_irq_restore() pair with
a lockdep assertion that interrupts are already disabled.  This should
remove the corresponding overhead from the interrupt entry/exit fastpaths.

This change was inspired by the fact that Iftekhar Ahmed's mutation
testing showed that removing rcu_irq_enter()'s call to local_ird_restore()
had no effect, which might indicate that interrupts were always enabled
anyway.

Signed-off-by: Paul E. McKenney

rcu: Make cpu_needs_another_gp() be bool

2015-12-08T01:01:31+00:00

The cpu_needs_another_gp() function is currently of type int, but only
returns zero or one.  Bow to reality and make it be of type bool.

Signed-off-by: Paul E. McKenney

rcu: Eliminate unused rcu_init_one() argument

2015-12-08T01:01:19+00:00

Now that the rcu_state structure's ->rda field is compile-time initialized,
there is no need to pass the per-CPU rcu_data structure into rcu_init_one().
This commit therefore eliminates this now-unused parameter.

Signed-off-by: Paul E. McKenney

rcutorture: Print symbolic name for ->gp_state

2015-12-06T01:58:26+00:00

Currently, ->gp_state is printed as an integer, which slows debugging.
This commit therefore prints a symbolic name in addition to the integer.

Signed-off-by: Paul E. McKenney 
[ paulmck: Updated to fix relational operator called out by Dan Carpenter. ]
[ paulmck: More "const", as suggested by Josh Triplett. ]
Reviewed-by: Josh Triplett

rcutorture: Dump stack when GP kthread stalls

2015-12-06T01:58:05+00:00

This commit increases debug information in the case where the grace-period
kthread is being prevented from running by dumping that kthread's stack.

Signed-off-by: Paul E. McKenney 
[ paulmck: Split into prior commit and this commit, as suggested by
  Josh Triplett. ]
Reviewed-by: Josh Triplett

rcutorture: Flag nonexistent RCU GP kthread

2015-12-06T01:58:00+00:00

Currently, if the RCU grace-period kthread has not yet been created,
in which case the starvation-check code will print zero for the state,
which maps to TASK_RUNNING.  This could clearly be quite confusing, so
this commit prints ~0, which does not map to any legal ->state value.

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

rcu: Stop disabling interrupts in scheduler fastpaths

2015-12-04T20:27:31+00:00

We need the scheduler's fastpaths to be, well, fast, and unnecessarily
disabling and re-enabling interrupts is not necessarily consistent with
this goal.  Especially given that there are regions of the scheduler that
already have interrupts disabled.

This commit therefore moves the call to rcu_note_context_switch()
to one of the interrupts-disabled regions of the scheduler, and
removes the now-redundant disabling and re-enabling of interrupts from
rcu_note_context_switch() and the functions it calls.

Reported-by: Peter Zijlstra 
Signed-off-by: Paul E. McKenney 
[ paulmck: Shift rcu_note_context_switch() to avoid deadlock, as suggested
  by Peter Zijlstra. ]