tree 8c53dca02da179c0a43735020c77e6df9d4c6117
parent 0c81b2a1448bc6a2a9b2d6469fb0669fb4b25e5b
author Lai Jiangshan <laijs@cn.fujitsu.com> 1214446003 +0800
committer Ingo Molnar <mingo@elte.hu> 1215983537 +0200

rcu classic: update qlen when cpu offline

When callbacks are moved from offline cpu to this cpu,
the qlen field of this rdp should be updated.

[ Paul E. McKenney: ]

The effect of this bug would be for force_quiescent_state() to be invoked
when it should not and vice versa -- wasting cycles in the first case
and letting RCU callbacks remain piled up in the second case.  The bug
is thus "benign" in that it does not result in premature grace-period
termination, but should of course be fixed nonetheless.

Preemption is disabled by the caller's get_cpu_var(), so we are guaranteed
to remain on the same CPU, as required.  The local_irq_disable() is indeed
needed, otherwise, an interrupt might invoke call_rcu() or call_rcu_bh(),
which could cause that interrupt's increment of ->qlen to be lost.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>