linux-kernel - [tip:x86/urgent] x86-64: Use the proper register width in call_rwsem

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Message-ID: <tip-50db45f2f010e9251dae644c5fb86b321d9ac815@git.kernel.org>
Date:	Tue, 4 May 2010 18:33:41 GMT
From:	tip-bot for David Howells <dhowells@...hat.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...hat.com,
	dhowells@...hat.com, tglx@...utronix.de
Subject: [tip:x86/urgent] x86-64: Use the proper register width in call_rwsem_wait()

Commit-ID:  50db45f2f010e9251dae644c5fb86b321d9ac815
Gitweb:     http://git.kernel.org/tip/50db45f2f010e9251dae644c5fb86b321d9ac815
Author:     David Howells <dhowells@...hat.com>
AuthorDate: Tue, 4 May 2010 13:42:53 +0100
Committer:  H. Peter Anvin <hpa@...or.com>
CommitDate: Tue, 4 May 2010 10:15:54 -0700

x86-64: Use the proper register width in call_rwsem_wait()

The x86_64 call_rwsem_wait() treats the active state counter part of the R/W
semaphore state as being 16-bit when it's actually 32-bit (it's half of the
64-bit state).  It should do "decl %edx" not "decw %dx".

[ hpa note: decl %edx will clear the upper half of %rdx, but the value of
  %rdx is dead after this point so that is OK. ]

Signed-off-by: David Howells <dhowells@...hat.com>
LKML-Reference: <20100504124253.30994.79841.stgit@...thog.procyon.org.uk>
Signed-off-by: H. Peter Anvin <hpa@...or.com>
---
 arch/x86/lib/rwsem_64.S |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/arch/x86/lib/rwsem_64.S b/arch/x86/lib/rwsem_64.S
index 15acecf..41fcf00 100644
--- a/arch/x86/lib/rwsem_64.S
+++ b/arch/x86/lib/rwsem_64.S
@@ -60,7 +60,7 @@ ENTRY(call_rwsem_down_write_failed)
 	ENDPROC(call_rwsem_down_write_failed)
 
 ENTRY(call_rwsem_wake)
-	decw %dx    /* do nothing if still outstanding active readers */
+	decl %edx	/* do nothing if still outstanding active readers */
 	jnz 1f
 	save_common_regs
 	movq %rax,%rdi
--
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