3.2.62-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Peter Zijlstra <peterz@infradead.org>

commit 4badad352a6bb202ec68afa7a574c0bb961e5ebc upstream.

The optimistic spin code assumes regular stores and cmpxchg() play nice;
this is found to not be true for at least: parisc, sparc32, tile32,
metag-lock1, arc-!llsc and hexagon.

There is further wreckage, but this in particular seemed easy to
trigger, so blacklist this.

Opt in for known good archs.

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Reported-by: Mikulas Patocka <mpatocka@redhat.com>
Cc: David Miller <davem@davemloft.net>
Cc: Chris Metcalf <redacted>
Cc: James Bottomley <James.Bottomley@hansenpartnership.com>
Cc: Vineet Gupta <redacted>
Cc: Jason Low <redacted>
Cc: Waiman Long <redacted>
Cc: "James E.J. Bottomley" <redacted>
Cc: Paul McKenney <redacted>
Cc: John David Anglin <redacted>
Cc: James Hogan <redacted>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Davidlohr Bueso <redacted>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Russell King <redacted>
Cc: Will Deacon <redacted>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: sparclinux@vger.kernel.org
Link: http://lkml.kernel.org/r/20140606175316.GV13930@laptop.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
[bwh: Backported to 3.2:
 - Adjust context
 - Drop arm64 change]
Signed-off-by: Ben Hutchings <redacted>
---

--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig

@@ -1,6 +1,7 @@
 config ARM
 	bool
 	default y
+	select ARCH_SUPPORTS_ATOMIC_RMW
 	select HAVE_DMA_API_DEBUG
 	select HAVE_IDE if PCI || ISA || PCMCIA
 	select HAVE_MEMBLOCK
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig

@@ -137,6 +137,7 @@ config PPC
 	select HAVE_BPF_JIT if (PPC64 && NET)
 	select HAVE_ARCH_JUMP_LABEL
 	select ARCH_HAVE_NMI_SAFE_CMPXCHG
+	select ARCH_SUPPORTS_ATOMIC_RMW
 
 config EARLY_PRINTK
 	bool
--- a/arch/sparc/Kconfig
+++ b/arch/sparc/Kconfig

@@ -57,6 +57,7 @@ config SPARC64
 	select IRQ_PREFLOW_FASTEOI
 	select ARCH_HAVE_NMI_SAFE_CMPXCHG
 	select HAVE_C_RECORDMCOUNT
+	select ARCH_SUPPORTS_ATOMIC_RMW
 
 config ARCH_DEFCONFIG
 	string
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig

@@ -75,6 +75,7 @@ config X86
 	select HAVE_BPF_JIT if (X86_64 && NET)
 	select CLKEVT_I8253
 	select ARCH_HAVE_NMI_SAFE_CMPXCHG
+	select ARCH_SUPPORTS_ATOMIC_RMW
 
 config INSTRUCTION_DECODER
 	def_bool (KPROBES || PERF_EVENTS)
--- a/kernel/Kconfig.locks
+++ b/kernel/Kconfig.locks

@@ -198,5 +198,9 @@ config INLINE_WRITE_UNLOCK_IRQ
 config INLINE_WRITE_UNLOCK_IRQRESTORE
 	def_bool !DEBUG_SPINLOCK && ARCH_INLINE_WRITE_UNLOCK_IRQRESTORE
 
+config ARCH_SUPPORTS_ATOMIC_RMW
+	bool
+
 config MUTEX_SPIN_ON_OWNER
-	def_bool SMP && !DEBUG_MUTEXES
+	def_bool y
+	depends on SMP && !DEBUG_MUTEXES && ARCH_SUPPORTS_ATOMIC_RMW