Messages in this thread Patch in this message | | | Date | Fri, 26 Feb 2016 16:35:57 -0500 | From | Steven Rostedt <> | Subject | [PATCH RT 06/10] net: Make synchronize_rcu_expedited() conditional on !RT_FULL |
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3.14.61-rt63-rc1 stable review patch. If anyone has any objections, please let me know.
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From: Josh Cartwright <joshc@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 <paulmck@linux.vnet.ibm.com> Signed-off-by: Josh Cartwright <joshc@ni.com> Cc: bigeasy@linutronix.de Acked-by: Eric Dumazet <eric.dumazet@gmail.com> Acked-by: David S. Miller <davem@davemloft.net> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Link: http://lkml.kernel.org/r/20151027123153.GG8245@jcartwri.amer.corp.natinst.com Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Steven Rostedt <rostedt@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
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