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Date:	Thu, 23 Dec 2010 13:43:20 +0800
From:	Huang Ying <ying.huang@...el.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org, Andi Kleen <andi@...stfloor.org>,
	ying.huang@...el.com, Peter Zijlstra <peterz@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	Richard Henderson <rth@...ddle.net>,
	Russell King <linux@....linux.org.uk>,
	Mikael Starvik <starvik@...s.com>,
	David Howells <dhowells@...hat.com>,
	Yoshinori Sato <ysato@...rs.sourceforge.jp>,
	Tony Luck <tony.luck@...el.com>,
	Hirokazu Takata <takata@...ux-m32r.org>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Michal Simek <monstr@...str.eu>,
	Ralf Baechle <ralf@...ux-mips.org>,
	Kyle McMartin <kyle@...artin.ca>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Chen Liqin <liqin.chen@...plusct.com>,
	"David S. Miller" <davem@...emloft.net>,
	Ingo Molnar <mingo@...hat.com>, Chris Zankel <chris@...kel.net>
Subject: [RFC -v9 1/4] Add Kconfig option ARCH_HAVE_NMI_SAFE_CMPXCHG

cmpxchg() is widely used by lockless code, including NMI-safe lockless
code.  But on some architectures, the cmpxchg() implementation is not
NMI-safe, on these architectures the lockless code may need to a
spin_trylock_irqsave() based implementation.

This patch adds a Kconfig option: ARCH_HAVE_NMI_SAFE_CMPXCHG, so that
NMI-safe lockless code can depend on it or provide different
implementation according to it.

On many architectures, cmpxchg is only NMI-safe for several specific
operand sizes. So, ARCH_HAVE_NMI_SAFE_CMPXCHG define in this patch
only guarantees cmpxchg is NMI-safe for sizeof(unsigned long).

Signed-off-by: Huang Ying <ying.huang@...el.com>
Acked-by: Mike Frysinger <vapier@...too.org>
Acked-by: Paul Mundt <lethal@...ux-sh.org>
Acked-by: Hans-Christian Egtvedt <hans-christian.egtvedt@...el.com>
Acked-by: Benjamin Herrenschmidt <benh@...nel.crashing.org>
Acked-by: Chris Metcalf <cmetcalf@...era.com>
CC: Richard Henderson <rth@...ddle.net>
CC: Russell King <linux@....linux.org.uk>
CC: Mikael Starvik <starvik@...s.com>
CC: David Howells <dhowells@...hat.com>
CC: Yoshinori Sato <ysato@...rs.sourceforge.jp>
CC: Tony Luck <tony.luck@...el.com>
CC: Hirokazu Takata <takata@...ux-m32r.org>
CC: Geert Uytterhoeven <geert@...ux-m68k.org>
CC: Michal Simek <monstr@...str.eu>
CC: Ralf Baechle <ralf@...ux-mips.org>
CC: Kyle McMartin <kyle@...artin.ca>
CC: Martin Schwidefsky <schwidefsky@...ibm.com>
CC: Chen Liqin <liqin.chen@...plusct.com>
CC: "David S. Miller" <davem@...emloft.net>
CC: Ingo Molnar <mingo@...hat.com>
CC: Chris Zankel <chris@...kel.net>
---
 arch/Kconfig         |    3 +++
 arch/alpha/Kconfig   |    1 +
 arch/avr32/Kconfig   |    1 +
 arch/frv/Kconfig     |    1 +
 arch/ia64/Kconfig    |    1 +
 arch/m68k/Kconfig    |    1 +
 arch/parisc/Kconfig  |    1 +
 arch/powerpc/Kconfig |    1 +
 arch/s390/Kconfig    |    1 +
 arch/sh/Kconfig      |    1 +
 arch/sparc/Kconfig   |    1 +
 arch/tile/Kconfig    |    1 +
 arch/x86/Kconfig     |    1 +
 13 files changed, 15 insertions(+)

--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -175,4 +175,7 @@ config HAVE_PERF_EVENTS_NMI
 config HAVE_ARCH_JUMP_LABEL
 	bool
 
+config ARCH_HAVE_NMI_SAFE_CMPXCHG
+	bool
+
 source "kernel/gcov/Kconfig"
--- a/arch/alpha/Kconfig
+++ b/arch/alpha/Kconfig
@@ -7,6 +7,7 @@ config ALPHA
 	select HAVE_SYSCALL_WRAPPERS
 	select HAVE_IRQ_WORK
 	select HAVE_PERF_EVENTS
+	select ARCH_HAVE_NMI_SAFE_CMPXCHG
 	select HAVE_DMA_ATTRS
 	help
 	  The Alpha is a 64-bit general-purpose processor designed and
--- a/arch/avr32/Kconfig
+++ b/arch/avr32/Kconfig
@@ -6,6 +6,7 @@ config AVR32
 	select HAVE_CLK
 	select HAVE_OPROFILE
 	select HAVE_KPROBES
+	select ARCH_HAVE_NMI_SAFE_CMPXCHG
 	help
 	  AVR32 is a high-performance 32-bit RISC microprocessor core,
 	  designed for cost-sensitive embedded applications, with particular
--- a/arch/frv/Kconfig
+++ b/arch/frv/Kconfig
@@ -5,6 +5,7 @@ config FRV
 	select HAVE_ARCH_TRACEHOOK
 	select HAVE_IRQ_WORK
 	select HAVE_PERF_EVENTS
+	select ARCH_HAVE_NMI_SAFE_CMPXCHG
 
 config ZONE_DMA
 	bool
--- a/arch/ia64/Kconfig
+++ b/arch/ia64/Kconfig
@@ -22,6 +22,7 @@ config IA64
 	select HAVE_KVM
 	select HAVE_ARCH_TRACEHOOK
 	select HAVE_DMA_API_DEBUG
+	select ARCH_HAVE_NMI_SAFE_CMPXCHG
 	default y
 	help
 	  The Itanium Processor Family is Intel's 64-bit successor to
--- a/arch/m68k/Kconfig
+++ b/arch/m68k/Kconfig
@@ -4,6 +4,7 @@ config M68K
 	select HAVE_AOUT
 	select HAVE_IDE
 	select GENERIC_ATOMIC64
+	select ARCH_HAVE_NMI_SAFE_CMPXCHG if RMW_INSNS
 
 config MMU
 	bool
--- a/arch/parisc/Kconfig
+++ b/arch/parisc/Kconfig
@@ -11,6 +11,7 @@ config PARISC
 	select BUG
 	select HAVE_IRQ_WORK
 	select HAVE_PERF_EVENTS
+	select ARCH_HAVE_NMI_SAFE_CMPXCHG
 	select GENERIC_ATOMIC64 if !64BIT
 	select GENERIC_HARDIRQS_NO__DO_IRQ
 	help
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -138,6 +138,7 @@ config PPC
 	select GENERIC_ATOMIC64 if PPC32
 	select HAVE_IRQ_WORK
 	select HAVE_PERF_EVENTS
+	select ARCH_HAVE_NMI_SAFE_CMPXCHG
 	select HAVE_REGS_AND_STACK_ACCESS_API
 	select HAVE_HW_BREAKPOINT if PERF_EVENTS && PPC_BOOK3S_64
 
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -94,6 +94,7 @@ config S390
 	select INIT_ALL_POSSIBLE
 	select HAVE_IRQ_WORK
 	select HAVE_PERF_EVENTS
+	select ARCH_HAVE_NMI_SAFE_CMPXCHG
 	select HAVE_KERNEL_GZIP
 	select HAVE_KERNEL_BZIP2
 	select HAVE_KERNEL_LZMA
--- a/arch/sh/Kconfig
+++ b/arch/sh/Kconfig
@@ -11,6 +11,7 @@ config SUPERH
 	select HAVE_DMA_ATTRS
 	select HAVE_IRQ_WORK
 	select HAVE_PERF_EVENTS
+	select ARCH_HAVE_NMI_SAFE_CMPXCHG if (GUSA_RB || CPU_SH4A)
 	select PERF_USE_VMALLOC
 	select HAVE_KERNEL_GZIP
 	select HAVE_KERNEL_BZIP2
--- a/arch/sparc/Kconfig
+++ b/arch/sparc/Kconfig
@@ -22,6 +22,7 @@ config SPARC
 	select RTC_CLASS
 	select RTC_DRV_M48T59
 	select HAVE_IRQ_WORK
+	select ARCH_HAVE_NMI_SAFE_CMPXCHG
 	select HAVE_DMA_ATTRS
 	select HAVE_DMA_API_DEBUG
 	select HAVE_ARCH_JUMP_LABEL
--- a/arch/tile/Kconfig
+++ b/arch/tile/Kconfig
@@ -104,6 +104,7 @@ config TILE
 	select GENERIC_FIND_NEXT_BIT
 	select USE_GENERIC_SMP_HELPERS
 	select CC_OPTIMIZE_FOR_SIZE
+	select ARCH_HAVE_NMI_SAFE_CMPXCHG
 
 # FIXME: investigate whether we need/want these options.
 #	select HAVE_IOREMAP_PROT
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -23,6 +23,7 @@ config X86
 	select HAVE_OPROFILE
 	select HAVE_PERF_EVENTS
 	select HAVE_IRQ_WORK
+	select ARCH_HAVE_NMI_SAFE_CMPXCHG if !M386
 	select HAVE_IOREMAP_PROT
 	select HAVE_KPROBES
 	select HAVE_MEMBLOCK
--
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