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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2018-01-31 19:40:22 -0800
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2018-02-20 16:12:28 -0800
commit7f5d42d05155523a4c42c2c5170f2a368217aed5 (patch)
tree622ba4ed926c9ec62fb2b40a0063db2b0050c7c7 /kernel/rcu/tree_exp.h
parent9a414201ae7ea089699a0cbd36533345ca17233b (diff)
rcu: Trace expedited GP delays due to transitioning CPUs
If a CPU is transitioning to or from offline state, an expedited grace period may undergo a timed wait. This timed wait can unduly delay grace periods, so this commit adds a trace statement to make it visible. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'kernel/rcu/tree_exp.h')
-rw-r--r--kernel/rcu/tree_exp.h3
1 files changed, 2 insertions, 1 deletions
diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h
index 70ad12abde36..fecb6b6ab452 100644
--- a/kernel/rcu/tree_exp.h
+++ b/kernel/rcu/tree_exp.h
@@ -32,7 +32,7 @@ static void rcu_exp_gp_seq_start(struct rcu_state *rsp)
* Return then value that expedited-grace-period counter will have
* at the end of the current grace period.
*/
-static unsigned long rcu_exp_gp_seq_endval(struct rcu_state *rsp)
+static __maybe_unused unsigned long rcu_exp_gp_seq_endval(struct rcu_state *rsp)
{
return rcu_seq_endval(&rsp->expedited_sequence);
}
@@ -428,6 +428,7 @@ retry_ipi:
(rnp->expmask & mask)) {
/* Online, so delay for a bit and try again. */
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
+ trace_rcu_exp_grace_period(rsp->name, rcu_exp_gp_seq_endval(rsp), TPS("selectofl"));
schedule_timeout_uninterruptible(1);
goto retry_ipi;
}