linux-kernel - [PATCH tip/core/rcu 36/88] srcu: Print non-default exp

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Date:   Thu, 25 May 2017 14:59:09 -0700
From:   "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:     linux-kernel@...r.kernel.org
Cc:     mingo@...nel.org, jiangshanlai@...il.com, dipankar@...ibm.com,
        akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
        josh@...htriplett.org, tglx@...utronix.de, peterz@...radead.org,
        rostedt@...dmis.org, dhowells@...hat.com, edumazet@...gle.com,
        fweisbec@...il.com, oleg@...hat.com, bobby.prani@...il.com,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: [PATCH tip/core/rcu 36/88] srcu: Print non-default exp_holdoff values at boot time

This commit makes srcu_bootup_announce() check for non-default values
of the auto-expedite holdoff time exp_holdoff and print a message if so.

Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
---
 kernel/rcu/srcutree.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index 021a9521a8b8..a46142de5133 100644
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -40,7 +40,9 @@
 #include "rcu.h"
 #include "rcu_segcblist.h"
 
-static ulong exp_holdoff = 25 * 1000; /* Holdoff (ns) for auto-expediting. */
+/* Holdoff in nanoseconds for auto-expediting. */
+#define DEFAULT_SRCU_EXP_HOLDOFF (25 * 1000)
+static ulong exp_holdoff = DEFAULT_SRCU_EXP_HOLDOFF;
 module_param(exp_holdoff, ulong, 0444);
 
 static void srcu_invoke_callbacks(struct work_struct *work);
@@ -1172,6 +1174,8 @@ EXPORT_SYMBOL_GPL(srcutorture_get_gp_data);
 static int __init srcu_bootup_announce(void)
 {
 	pr_info("Hierarchical SRCU implementation.\n");
+	if (exp_holdoff != DEFAULT_SRCU_EXP_HOLDOFF)
+		pr_info("\tNon-default auto-expedite holdoff of %lu ns.\n", exp_holdoff);
 	return 0;
 }
 early_initcall(srcu_bootup_announce);
-- 
2.5.2