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Message-Id: <1445886895-3692-1-git-send-email-joshc@ni.com> Date: Mon, 26 Oct 2015 14:14:55 -0500 From: Josh Cartwright <joshc@...com> To: tglx@...utronix.de, bigeasy@...utronix.de Cc: linux-rt-users@...r.kernel.org, linux-kernel@...r.kernel.org, Eric Dumazet <eric.dumazet@...il.com>, "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>, "David S. Miller" <davem@...emloft.net> Subject: [PATCH -rt] Revert "net: use synchronize_rcu_expedited()" This reverts commit be3fc413da9eb17cce0991f214ab019d16c88c41. 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 be3fc413da9e reverted, we can observe a latency spike up to 30us with cyclictest by rapidly unplugging/reestablishing an ethernet link. Cc: Eric Dumazet <eric.dumazet@...il.com> Cc: Paul E. McKenney <paulmck@...ux.vnet.ibm.com> Cc: David S. Miller <davem@...emloft.net> Signed-off-by: Josh Cartwright <joshc@...com> --- net/core/dev.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-) diff --git a/net/core/dev.c b/net/core/dev.c index f8c23de..869ef62 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -6969,10 +6969,7 @@ EXPORT_SYMBOL(free_netdev); void synchronize_net(void) { might_sleep(); - if (rtnl_is_locked()) - synchronize_rcu_expedited(); - else - synchronize_rcu(); + synchronize_rcu(); } EXPORT_SYMBOL(synchronize_net); -- 2.5.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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