atomic64: no need for CONFIG_ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE

This came to light when implementing native 64-bit atomics for ARCv2.

The atomic64 self-test code uses CONFIG_ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE
to check whether atomic64_dec_if_positive() is available.  It seems it
was needed when not every arch defined it.  However as of current code
the Kconfig option seems needless

 - for CONFIG_GENERIC_ATOMIC64 it is auto-enabled in lib/Kconfig and a
   generic definition of API is present lib/atomic64.c
 - arches with native 64-bit atomics select it in arch/*/Kconfig and
   define the API in their headers

So I see no point in keeping the Kconfig option

Compile tested for:
 - blackfin (CONFIG_GENERIC_ATOMIC64)
 - x86 (!CONFIG_GENERIC_ATOMIC64)
 - ia64

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Vineet Gupta <[email protected]>
Cc: Richard Henderson <[email protected]>
Cc: Ivan Kokshaysky <[email protected]>
Cc: Matt Turner <[email protected]>
Cc: Russell King <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Ralf Baechle <[email protected]>
Cc: "James E.J. Bottomley" <[email protected]>
Cc: Helge Deller <[email protected]>
Cc: Benjamin Herrenschmidt <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Michael Ellerman <[email protected]>
Cc: Martin Schwidefsky <[email protected]>
Cc: Heiko Carstens <[email protected]>
Cc: "David S. Miller" <[email protected]>
Cc: Chris Metcalf <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Vineet Gupta <[email protected]>
Cc: Zhaoxiu Zeng <[email protected]>
Cc: Linus Walleij <[email protected]>
Cc: Alexander Potapenko <[email protected]>
Cc: Andrey Ryabinin <[email protected]>
Cc: Herbert Xu <[email protected]>
Cc: Ming Lin <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Geert Uytterhoeven <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Boqun Feng <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

arch/alpha/Kconfig

@@ -15,7 +15,6 @@ config ALPHA
 	select GENERIC_IRQ_SHOW
 	select ARCH_WANT_IPC_PARSE_VERSION
 	select ARCH_HAVE_NMI_SAFE_CMPXCHG
-	select ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE
 	select AUDIT_ARCH
 	select GENERIC_CLOCKEVENTS
 	select GENERIC_SMP_IDLE_THREAD

arch/arm/Kconfig

@@ -2,7 +2,6 @@ config ARM
 	bool
 	default y
 	select ARCH_CLOCKSOURCE_DATA
-	select ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE
 	select ARCH_HAS_DEVMEM_IS_ALLOWED
 	select ARCH_HAS_ELF_RANDOMIZE
 	select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST

arch/arm64/Kconfig

@@ -8,7 +8,6 @@ config ARM64
 	select ARCH_CLOCKSOURCE_DATA
 	select ARCH_HAS_DEVMEM_IS_ALLOWED
 	select ARCH_HAS_ACPI_TABLE_UPGRADE if ACPI
-	select ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE
 	select ARCH_HAS_ELF_RANDOMIZE
 	select ARCH_HAS_GCOV_PROFILE_ALL
 	select ARCH_HAS_GIGANTIC_PAGE

arch/mips/Kconfig

@@ -30,7 +30,6 @@ config MIPS
 	select HAVE_ARCH_TRANSPARENT_HUGEPAGE if CPU_SUPPORTS_HUGEPAGES && 64BIT
 	select RTC_LIB if !MACH_LOONGSON64
 	select GENERIC_ATOMIC64 if !64BIT
-	select ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE
 	select HAVE_DMA_CONTIGUOUS
 	select HAVE_DMA_API_DEBUG
 	select GENERIC_IRQ_PROBE

arch/parisc/Kconfig

@@ -14,7 +14,6 @@ config PARISC
 	select BUILDTIME_EXTABLE_SORT
 	select HAVE_PERF_EVENTS
 	select GENERIC_ATOMIC64 if !64BIT
-	select ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE
 	select BROKEN_RODATA
 	select GENERIC_IRQ_PROBE
 	select GENERIC_PCI_IOMAP

arch/powerpc/Kconfig

@@ -113,7 +113,6 @@ config PPC
 	select HAVE_DEBUG_KMEMLEAK
 	select ARCH_HAS_SG_CHAIN
 	select GENERIC_ATOMIC64 if PPC32
-	select ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE
 	select HAVE_PERF_EVENTS
 	select HAVE_PERF_REGS
 	select HAVE_PERF_USER_STACK_DUMP

arch/s390/Kconfig

@@ -67,7 +67,6 @@ config DEBUG_RODATA
 
 config S390
 	def_bool y
-	select ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE
 	select ARCH_HAS_DEVMEM_IS_ALLOWED
 	select ARCH_HAS_ELF_RANDOMIZE
 	select ARCH_HAS_GCOV_PROFILE_ALL

arch/sparc/Kconfig

@@ -22,7 +22,6 @@ config SPARC
 	select HAVE_ARCH_TRACEHOOK
 	select HAVE_EXIT_THREAD
 	select SYSCTL_EXCEPTION_TRACE
-	select ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE
 	select RTC_CLASS
 	select RTC_DRV_M48T59
 	select RTC_SYSTOHC

arch/tile/Kconfig

@@ -3,7 +3,6 @@
 
 config TILE
 	def_bool y
-	select ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE
 	select ARCH_HAS_DEVMEM_IS_ALLOWED
 	select ARCH_HAVE_NMI_SAFE_CMPXCHG
 	select ARCH_WANT_FRAME_POINTERS

arch/x86/Kconfig

@@ -23,7 +23,6 @@ config X86
 	select ARCH_CLOCKSOURCE_DATA
 	select ARCH_DISCARD_MEMBLOCK
 	select ARCH_HAS_ACPI_TABLE_UPGRADE if ACPI
-	select ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE
 	select ARCH_HAS_DEVMEM_IS_ALLOWED
 	select ARCH_HAS_ELF_RANDOMIZE
 	select ARCH_HAS_FAST_MULTIPLIER

lib/Kconfig

@@ -457,9 +457,6 @@ config NLATTR
 config GENERIC_ATOMIC64
        bool
 
-config ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE
-	def_bool y if GENERIC_ATOMIC64
-
 config LRU_CACHE
 	tristate
 

lib/atomic64_test.c

@@ -213,7 +213,6 @@ static __init void test_atomic64(void)
 	r += one;
 	BUG_ON(v.counter != r);
 
-#ifdef CONFIG_ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE
 	INIT(onestwos);
 	BUG_ON(atomic64_dec_if_positive(&v) != (onestwos - 1));
 	r -= one;
@@ -226,9 +225,6 @@ static __init void test_atomic64(void)
 	INIT(-one);
 	BUG_ON(atomic64_dec_if_positive(&v) != (-one - one));
 	BUG_ON(v.counter != r);
-#else
-#warning Please implement atomic64_dec_if_positive for your architecture and select the above Kconfig symbol
-#endif
 
 	INIT(onestwos);
 	BUG_ON(!atomic64_inc_not_zero(&v));