linux-kernel - [PATCH 2/4 V2] rcu: use "int trycount" instead of "bool expedited"

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Date:	Mon, 19 Mar 2012 16:12:12 +0800
From:	Lai Jiangshan <laijs@...fujitsu.com>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:	Lai Jiangshan <laijs@...fujitsu.com>, linux-kernel@...r.kernel.org,
	mingo@...e.hu, dipankar@...ibm.com, akpm@...ux-foundation.org,
	mathieu.desnoyers@...ymtl.ca, josh@...htriplett.org,
	niv@...ibm.com, tglx@...utronix.de, peterz@...radead.org,
	rostedt@...dmis.org, Valdis.Kletnieks@...edu, dhowells@...hat.com,
	eric.dumazet@...il.com, darren@...art.com, fweisbec@...il.com,
	patches@...aro.org
Subject: [PATCH 2/4 V2] rcu: use "int trycount" instead of "bool expedited"

Use the value of trycount for the strategy for expedited or not in srcu.

Signed-off-by: Lai Jiangshan <laijs@...fujitsu.com>
---
 kernel/srcu.c |   27 ++++++++++++++-------------
 1 files changed, 14 insertions(+), 13 deletions(-)

diff --git a/kernel/srcu.c b/kernel/srcu.c
index 9e86ed7..2923541 100644
--- a/kernel/srcu.c
+++ b/kernel/srcu.c
@@ -251,16 +251,16 @@ EXPORT_SYMBOL_GPL(__srcu_read_unlock);
  * we repeatedly block for 1-millisecond time periods.  This approach
  * has done well in testing, so there is no need for a config parameter.
  */
-#define SYNCHRONIZE_SRCU_READER_DELAY 5
+#define SYNCHRONIZE_SRCU_READER_DELAY	5
+#define SYNCHRONIZE_SRCU_TRYCOUNT	2
+#define SYNCHRONIZE_SRCU_EXP_TRYCOUNT	12
 
 /*
  * Wait until all the readers(which starts before this wait_idx()
  * with the specified idx) complete.
  */
-static void wait_idx(struct srcu_struct *sp, int idx, bool expedited)
+static void wait_idx(struct srcu_struct *sp, int idx, int trycount)
 {
-	int trycount = 0;
-
 	/*
 	 * SRCU read-side critical sections are normally short, so wait
 	 * a small amount of time before possibly blocking.
@@ -268,9 +268,10 @@ static void wait_idx(struct srcu_struct *sp, int idx, bool expedited)
 	if (!srcu_readers_active_idx_check(sp, idx)) {
 		udelay(SYNCHRONIZE_SRCU_READER_DELAY);
 		while (!srcu_readers_active_idx_check(sp, idx)) {
-			if (expedited && ++ trycount < 10)
+			if (trycount > 0) {
+				trycount--;
 				udelay(SYNCHRONIZE_SRCU_READER_DELAY);
-			else
+			} else
 				schedule_timeout_interruptible(1);
 		}
 	}
@@ -284,7 +285,7 @@ static void srcu_flip(struct srcu_struct *sp)
 /*
  * Helper function for synchronize_srcu() and synchronize_srcu_expedited().
  */
-static void __synchronize_srcu(struct srcu_struct *sp, bool expedited)
+static void __synchronize_srcu(struct srcu_struct *sp, int trycount)
 {
 	int busy_idx;
 
@@ -301,8 +302,8 @@ static void __synchronize_srcu(struct srcu_struct *sp, bool expedited)
 	 * There are some readers start with idx=0, and some others start
 	 * with idx=1. So two wait_idx()s are enough for synchronize:
 	 * __synchronize_srcu() {
-	 * 	wait_idx(sp, 0, expedited);
-	 * 	wait_idx(sp, 1, expedited);
+	 * 	wait_idx(sp, 0, trycount);
+	 * 	wait_idx(sp, 1, trycount);
 	 * }
 	 * When it returns, all started readers have complete.
 	 *
@@ -331,7 +332,7 @@ static void __synchronize_srcu(struct srcu_struct *sp, bool expedited)
 	 * Because this probability is not high, wait_idx()
 	 * will normally not need to wait.
 	 */
-	wait_idx(sp, 1 - busy_idx, expedited);
+	wait_idx(sp, 1 - busy_idx, trycount);
 
 	/* flip the index to ensure the return of the next wait_idx() */
 	srcu_flip(sp);
@@ -339,7 +340,7 @@ static void __synchronize_srcu(struct srcu_struct *sp, bool expedited)
 	/*
 	 * Now that wait_idx() has waited for the really old readers.
 	 */
-	wait_idx(sp, busy_idx, expedited);
+	wait_idx(sp, busy_idx, trycount);
 
 	mutex_unlock(&sp->mutex);
 }
@@ -360,7 +361,7 @@ static void __synchronize_srcu(struct srcu_struct *sp, bool expedited)
  */
 void synchronize_srcu(struct srcu_struct *sp)
 {
-	__synchronize_srcu(sp, 0);
+	__synchronize_srcu(sp, SYNCHRONIZE_SRCU_TRYCOUNT);
 }
 EXPORT_SYMBOL_GPL(synchronize_srcu);
 
@@ -381,7 +382,7 @@ EXPORT_SYMBOL_GPL(synchronize_srcu);
  */
 void synchronize_srcu_expedited(struct srcu_struct *sp)
 {
-	__synchronize_srcu(sp, 1);
+	__synchronize_srcu(sp, SYNCHRONIZE_SRCU_EXP_TRYCOUNT);
 }
 EXPORT_SYMBOL_GPL(synchronize_srcu_expedited);
 
-- 
1.7.4.4

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