linux-kernel - [S390] Small barrier() and cpu

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Message-ID: <20070126165136.GO11609@skybase>
Date:	Fri, 26 Jan 2007 17:51:36 +0100
From:	Martin Schwidefsky <schwidefsky@...ibm.com>
To:	linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org
Cc:	heiko.carstens@...ibm.com
Subject: [S390] Small barrier() and cpu_relax() cleanup.

From: Heiko Carstens <heiko.carstens@...ibm.com>

[S390] Small barrier() and cpu_relax() cleanup.

cpu_relax() has barrier() semantics hence there is no need to use both
of them in conjunction in sclp_sync_wait(). Also change cpu_relax()
so it's more obvious that it has barrier semantics.

Signed-off-by: Heiko Carstens <heiko.carstens@...ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@...ibm.com>
---

 drivers/s390/char/sclp.c     |    1 -
 include/asm-s390/processor.h |    5 ++---
 2 files changed, 2 insertions(+), 4 deletions(-)

diff -urpN linux-2.6/drivers/s390/char/sclp.c linux-2.6-patched/drivers/s390/char/sclp.c
--- linux-2.6/drivers/s390/char/sclp.c	2007-01-26 17:27:59.000000000 +0100
+++ linux-2.6-patched/drivers/s390/char/sclp.c	2007-01-26 17:28:00.000000000 +0100
@@ -433,7 +433,6 @@ sclp_sync_wait(void)
 		    get_clock() > timeout &&
 		    del_timer(&sclp_request_timer))
 			sclp_request_timer.function(sclp_request_timer.data);
-		barrier();
 		cpu_relax();
 	}
 	local_irq_disable();
diff -urpN linux-2.6/include/asm-s390/processor.h linux-2.6-patched/include/asm-s390/processor.h
--- linux-2.6/include/asm-s390/processor.h	2006-11-29 22:57:37.000000000 +0100
+++ linux-2.6-patched/include/asm-s390/processor.h	2007-01-26 17:28:00.000000000 +0100
@@ -201,9 +201,8 @@ unsigned long get_wchan(struct task_stru
 static inline void cpu_relax(void)
 {
 	if (MACHINE_HAS_DIAG44)
-		asm volatile("diag 0,0,68" : : : "memory");
-	else
-		barrier();
+		asm volatile("diag 0,0,68");
+	barrier();
 }
 
 /*
-
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