48 lines
1.8 KiB
Diff
48 lines
1.8 KiB
Diff
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rcu: Avoid having just-onlined CPU resched itself when RCU is idle
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CPUs set rdp->qs_pending when coming online to resolve races with
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grace-period start. However, this means that if RCU is idle, the
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just-onlined CPU might needlessly send itself resched IPIs. Adjust
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the online-CPU initialization to avoid this, and also to correctly
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cause the CPU to respond to the current grace period if needed.
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Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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---
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kernel/rcutree.c | 13 +++++++++----
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1 files changed, 9 insertions(+), 4 deletions(-)
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diff --git a/kernel/rcutree.c b/kernel/rcutree.c
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index ba06207..472d6b2 100644
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--- a/kernel/rcutree.c
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+++ b/kernel/rcutree.c
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@@ -1865,8 +1865,6 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptible)
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/* Set up local state, ensuring consistent view of global state. */
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raw_spin_lock_irqsave(&rnp->lock, flags);
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- rdp->passed_quiesc = 0; /* We could be racing with new GP, */
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- rdp->qs_pending = 1; /* so set up to respond to current GP. */
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rdp->beenonline = 1; /* We have now been online. */
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rdp->preemptible = preemptible;
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rdp->qlen_last_fqs_check = 0;
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@@ -1891,8 +1889,15 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptible)
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rnp->qsmaskinit |= mask;
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mask = rnp->grpmask;
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if (rnp == rdp->mynode) {
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- rdp->gpnum = rnp->completed; /* if GP in progress... */
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- rdp->completed = rnp->completed;
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+ /*
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+ * If there is a grace period in progress, we will
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+ * set up to wait for it next time we run the
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+ * RCU core code.
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+ */
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+ rdp->gpnum = rnp->completed;
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+ rdp->completed = rnp->completed;
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+ rdp->passed_quiesc = 0;
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+ rdp->qs_pending = 0;
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rdp->passed_quiesc_completed = rnp->completed - 1;
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}
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raw_spin_unlock(&rnp->lock); /* irqs already disabled. */
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--
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1.7.6
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