linux-kernel - [PATCH v2 2/2] atomic64: No need for CONFIG_ARCH_HAS_ATOMIC64_DEC_IF

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Date:   Mon, 12 Sep 2016 10:47:12 -0700
From:   Vineet Gupta <Vineet.Gupta1@...opsys.com>
To:     Tony Luck <tony.luck@...el.com>, Fenghua Yu <fenghua.yu@...el.com>,
        "Ingo Molnar" <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>
CC:     <linux-kernel@...r.kernel.org>,
        <linux-snps-arc@...ts.infradead.org>,
        Vineet Gupta <Vineet.Gupta1@...opsys.com>,
        Richard Henderson <rth@...ddle.net>,
        Ivan Kokshaysky <ink@...assic.park.msu.ru>,
        Matt Turner <mattst88@...il.com>,
        Russell King <linux@...linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Ralf Baechle <ralf@...ux-mips.org>,
        "James E.J. Bottomley" <jejb@...isc-linux.org>,
        Helge Deller <deller@....de>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        "Michael Ellerman" <mpe@...erman.id.au>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        "David S. Miller" <davem@...emloft.net>,
        Chris Metcalf <cmetcalf@...lanox.com>,
        "Thomas Gleixner" <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, <x86@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Zhaoxiu Zeng <zhaoxiu.zeng@...il.com>,
        "Linus Walleij" <linus.walleij@...aro.org>,
        Matthew Wilcox <willy@...ux.intel.com>,
        Alexander Potapenko <glider@...gle.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Ming Lin <ming.l@....samsung.com>,
        Arnd Bergmann <arnd@...db.de>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Borislav Petkov <bp@...e.de>, Andi Kleen <ak@...ux.intel.com>,
        Boqun Feng <boqun.feng@...il.com>,
        <linux-alpha@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-mips@...ux-mips.org>, <linux-parisc@...r.kernel.org>,
        <linuxppc-dev@...ts.ozlabs.org>, <linux-s390@...r.kernel.org>,
        <sparclinux@...r.kernel.org>, <linux-arch@...r.kernel.org>
Subject: [PATCH v2 2/2] 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

Cc: Richard Henderson <rth@...ddle.net>
Cc: Ivan Kokshaysky <ink@...assic.park.msu.ru>
Cc: Matt Turner <mattst88@...il.com>
Cc: Russell King <linux@...linux.org.uk>
Cc: Catalin Marinas <catalin.marinas@....com>
Cc: Will Deacon <will.deacon@....com>
Cc: Ralf Baechle <ralf@...ux-mips.org>
Cc: "James E.J. Bottomley" <jejb@...isc-linux.org>
Cc: Helge Deller <deller@....de>
Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc: Paul Mackerras <paulus@...ba.org>
Cc: Michael Ellerman <mpe@...erman.id.au>
Cc: Martin Schwidefsky <schwidefsky@...ibm.com>
Cc: Heiko Carstens <heiko.carstens@...ibm.com>
Cc: "David S. Miller" <davem@...emloft.net>
Cc: Chris Metcalf <cmetcalf@...lanox.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: "H. Peter Anvin" <hpa@...or.com>
Cc: x86@...nel.org
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Vineet Gupta <vgupta@...opsys.com>
Cc: Zhaoxiu Zeng <zhaoxiu.zeng@...il.com>
Cc: Linus Walleij <linus.walleij@...aro.org>
Cc: Matthew Wilcox <willy@...ux.intel.com>
Cc: Alexander Potapenko <glider@...gle.com>
Cc: Andrey Ryabinin <aryabinin@...tuozzo.com>
Cc: Herbert Xu <herbert@...dor.apana.org.au>
Cc: Ming Lin <ming.l@....samsung.com>
Cc: Arnd Bergmann <arnd@...db.de>
Cc: Geert Uytterhoeven <geert@...ux-m68k.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Borislav Petkov <bp@...e.de>
Cc: Andi Kleen <ak@...ux.intel.com>
Cc: Boqun Feng <boqun.feng@...il.com>
Cc: linux-alpha@...r.kernel.org
Cc: linux-kernel@...r.kernel.org
Cc: linux-arm-kernel@...ts.infradead.org
Cc: linux-mips@...ux-mips.org
Cc: linux-parisc@...r.kernel.org
Cc: linuxppc-dev@...ts.ozlabs.org
Cc: linux-s390@...r.kernel.org
Cc: sparclinux@...r.kernel.org
Cc: linux-snps-arc@...ts.infradead.org
Cc: linux-arch@...r.kernel.org
Signed-off-by: Vineet Gupta <vgupta@...opsys.com>
---
 arch/alpha/Kconfig   | 1 -
 arch/arm/Kconfig     | 1 -
 arch/arm64/Kconfig   | 1 -
 arch/mips/Kconfig    | 1 -
 arch/parisc/Kconfig  | 1 -
 arch/powerpc/Kconfig | 1 -
 arch/s390/Kconfig    | 2 +-
 arch/sparc/Kconfig   | 1 -
 arch/tile/Kconfig    | 2 +-
 arch/x86/Kconfig     | 2 +-
 lib/Kconfig          | 3 ---
 lib/atomic64_test.c  | 4 ----
 12 files changed, 3 insertions(+), 17 deletions(-)

diff --git a/arch/alpha/Kconfig b/arch/alpha/Kconfig
index 7f312d80b43b..0e49d39ea74a 100644
--- a/arch/alpha/Kconfig
+++ b/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
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index a9c4e48bb7ec..2a50957c7bfb 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1,7 +1,6 @@
 config ARM
 	bool
 	default y
-	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
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index bc3f00f586f1..3df2ca7efbcc 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -6,7 +6,6 @@ config ARM64
 	select ACPI_MCFG if ACPI
 	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_KCOV
diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index 26388562e300..5bbea197c220 100644
--- a/arch/mips/Kconfig
+++ b/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
diff --git a/arch/parisc/Kconfig b/arch/parisc/Kconfig
index af12c2db9bb8..8a96bdcc3807 100644
--- a/arch/parisc/Kconfig
+++ b/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
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 927d2ab2ce08..18d1b42cf545 100644
--- a/arch/powerpc/Kconfig
+++ b/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
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index c109f073d454..af52b07efde2 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -67,7 +67,7 @@ config DEBUG_RODATA
 
 config S390
 	def_bool y
-	select ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE
+	select ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS
 	select ARCH_HAS_DEVMEM_IS_ALLOWED
 	select ARCH_HAS_ELF_RANDOMIZE
 	select ARCH_HAS_GCOV_PROFILE_ALL
diff --git a/arch/sparc/Kconfig b/arch/sparc/Kconfig
index 59b09600dd32..bfedbe0cb7b2 100644
--- a/arch/sparc/Kconfig
+++ b/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
diff --git a/arch/tile/Kconfig b/arch/tile/Kconfig
index 78da75b670bc..12eda5440c93 100644
--- a/arch/tile/Kconfig
+++ b/arch/tile/Kconfig
@@ -3,7 +3,7 @@
 
 config TILE
 	def_bool y
-	select ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE
+	select ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS
 	select ARCH_HAS_DEVMEM_IS_ALLOWED
 	select ARCH_HAVE_NMI_SAFE_CMPXCHG
 	select ARCH_WANT_FRAME_POINTERS
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 2a1f0ce7c59a..0cf609998550 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -23,7 +23,7 @@ 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_DEBUG_STRICT_USER_COPY_CHECKS
 	select ARCH_HAS_DEVMEM_IS_ALLOWED
 	select ARCH_HAS_ELF_RANDOMIZE
 	select ARCH_HAS_FAST_MULTIPLIER
diff --git a/lib/Kconfig b/lib/Kconfig
index d79909dc01ec..0e74df3c5441 100644
--- a/lib/Kconfig
+++ b/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
 
diff --git a/lib/atomic64_test.c b/lib/atomic64_test.c
index dbb369145dda..46042901130f 100644
--- a/lib/atomic64_test.c
+++ b/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));
-- 
2.7.4