3.14.61-rt63-rc1 stable review patch. If anyone has any objections, please let me know.
------------------ From: Josh Cartwright <jo...@ni.com> While the use of synchronize_rcu_expedited() might make synchronize_net() "faster", it does so at significant cost on RT systems, as expediting a grace period forcibly preempts any high-priority RT tasks (via the stop_machine() mechanism). Without this change, we can observe a latency spike up to 30us with cyclictest by rapidly unplugging/reestablishing an ethernet link. Suggested-by: Paul E. McKenney <paul...@linux.vnet.ibm.com> Signed-off-by: Josh Cartwright <jo...@ni.com> Cc: bige...@linutronix.de Acked-by: Eric Dumazet <eric.duma...@gmail.com> Acked-by: David S. Miller <da...@davemloft.net> Cc: Paul E. McKenney <paul...@linux.vnet.ibm.com> Link: http://lkml.kernel.org/r/20151027123153.gg8...@jcartwri.amer.corp.natinst.com Signed-off-by: Thomas Gleixner <t...@linutronix.de> Signed-off-by: Steven Rostedt <rost...@goodmis.org> --- net/core/dev.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/core/dev.c b/net/core/dev.c index 6febdc96835f..ddb8578b2f34 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -6638,7 +6638,7 @@ EXPORT_SYMBOL(free_netdev); void synchronize_net(void) { might_sleep(); - if (rtnl_is_locked()) + if (rtnl_is_locked() && !IS_ENABLED(CONFIG_PREEMPT_RT_FULL)) synchronize_rcu_expedited(); else synchronize_rcu(); -- 2.7.0
