From: Soby Mathew <soby.mathew@arm.com>
Date: Tue, 18 Nov 2014 10:45:04 +0000 (+0000)
Subject: Remove the wfe() for bounded wait in bakery_lock
X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=d4f4ad90f9fe754bc098bbb392ba780e5a1bb0b3;p=project%2Fbcm63xx%2Fatf.git

Remove the wfe() for bounded wait in bakery_lock

This patch is an optimization in the bakery_lock_get() function
which removes the wfe() when waiting for other contenders to choose
their ticket i.e when their `entering` flag is set. Since the time
taken to execute bakery_get_ticket() by other contenders is bounded,
this wait is a bounded time wait. Hence the removal of wfe() and the
corresponding sev() and dsb() in bakery_get_ticket() may result
in better time performance during lock acquisition.

Change-Id: I141bb21294226b54cb6e89e7cac0175c553afd8d
---

diff --git a/lib/locks/bakery/bakery_lock.c b/lib/locks/bakery/bakery_lock.c
index 7e71dec0..6bdc35a5 100644
--- a/lib/locks/bakery/bakery_lock.c
+++ b/lib/locks/bakery/bakery_lock.c
@@ -107,8 +107,6 @@ static unsigned int bakery_get_ticket(bakery_lock_t *bakery, unsigned int me)
 	++my_ticket;
 	bakery->number[me] = my_ticket;
 	bakery->entering[me] = 0;
-	dsb();
-	sev();
 
 	return my_ticket;
 }
@@ -151,7 +149,7 @@ void bakery_lock_get(bakery_lock_t *bakery)
 
 		/* Wait for the contender to get their ticket */
 		while (bakery->entering[they])
-			wfe();
+			;
 
 		/*
 		 * If the other party is a contender, they'll have non-zero