linux-kernel - [PATCH for 2.6.23] [2/3] x86_64: Remove CLFLUSH in text

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Date:	Thu,  6 Sep 2007 16:59:52 +0200 (CEST)
From:	Andi Kleen <ak@...e.de>
To:	patches@...-64.org, linux-kernel@...r.kernel.org, torvalds@...l.org
Subject: [PATCH for 2.6.23] [2/3] x86_64: Remove CLFLUSH in text_poke()


The CLFLUSH for the modified code line in text_poke was supposed
to speed up CPU recovery. Unfortunately it seems to cause hangs
on some VIA C3s (at least on VIA Esther Model 10 Stepping 9)
Remove it.

Thanks to Stefan Becker for reporting/testing.

Signed-off-by: Andi Kleen <ak@...e.de>

---
 arch/i386/kernel/alternative.c |    6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

Index: linux/arch/i386/kernel/alternative.c
===================================================================
--- linux.orig/arch/i386/kernel/alternative.c
+++ linux/arch/i386/kernel/alternative.c
@@ -445,8 +445,6 @@ void __kprobes text_poke(void *addr, uns
 {
 	memcpy(addr, opcode, len);
 	sync_core();
-	/* Not strictly needed, but can speed CPU recovery up. Ignore cross cacheline
-	   case. */
-	if (cpu_has_clflush)
-		asm("clflush (%0) " :: "r" (addr) : "memory");
+	/* Could also do a CLFLUSH here to speed up CPU recovery; but
+	   that causes hangs on some VIA CPUs. */
 }
-
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