3.18.27-rt26-rc1 stable review patch. If anyone has any objections, please let me know. ------------------ From: Josh Cartwright <joshc@xxxxxx> 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 <paulmck@xxxxxxxxxxxxxxxxxx> Signed-off-by: Josh Cartwright <joshc@xxxxxx> Cc: bigeasy@xxxxxxxxxxxxx Acked-by: Eric Dumazet <eric.dumazet@xxxxxxxxx> Acked-by: David S. Miller <davem@xxxxxxxxxxxxx> Cc: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> Link: http://lkml.kernel.org/r/20151027123153.GG8245@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx> --- 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 1cbcf08cc224..48872718d8e2 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -6813,7 +6813,7 @@ 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 -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
