cpu: Wait for RCU grace periods concurrently
authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Wed, 10 Jun 2015 20:34:41 +0000 (13:34 -0700)
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Wed, 22 Jul 2015 22:27:30 +0000 (15:27 -0700)
commit779de6ce54f627f955d4a3d0c5b3dcfaab74fea8
tree970e26e9d25d2beab184fb7c87e8ff1c5d348023
parentec90a194ae2cb8b8e9fe4f6f70dd3d4dc0269b4b
cpu: Wait for RCU grace periods concurrently

In kernels built with CONFIG_PREEMPT, _cpu_down() waits for RCU and
RCU-sched grace periods back-to-back, incurring quite a bit more latency
than required.  This commit therefore uses the new synchronize_rcu_mult()
to allow waiting for both grace periods concurrently.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
kernel/cpu.c