rcu: Stop disabling interrupts in scheduler fastpaths
authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Wed, 7 Oct 2015 16:10:48 +0000 (09:10 -0700)
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Fri, 4 Dec 2015 20:27:31 +0000 (12:27 -0800)
commit46a5d164db53ba6066b11889abb7fa6bddbe5cf7
tree37e726508f20e8dd951f04dd3266be912abc5b44
parentf0f2e7d307fff226e0c1df5a07101a1216a46d8a
rcu: Stop disabling interrupts in scheduler fastpaths

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 <peterz@infradead.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
[ paulmck: Shift rcu_note_context_switch() to avoid deadlock, as suggested
  by Peter Zijlstra. ]
include/linux/rcutree.h
kernel/rcu/tree.c
kernel/rcu/tree_plugin.h
kernel/sched/core.c