ARM: Emulate one-byte cmpxchg
Use the new cmpxchg_emu_u8() to emulate one-byte cmpxchg() on ARM systems with ARCH == ARMv6K. [ paulmck: Apply Arnd Bergmann and Nathan Chancellor feedback. ] [ paulmck: Apply Linus Walleij feedback. ] Reported-by: Mark Brown <broonie@kernel.org> Closes: https://lore.kernel.org/all/54798f68-48f7-4c65-9cba-47c0bf175143@sirena.org.uk/ Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org> Closes: https://lore.kernel.org/all/CA+G9fYuZ+pf6p8AXMZWtdFtX-gbG8HMaBKp=XbxcdzA_QeLkxQ@mail.gmail.com/ Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Tested-by: Nathan Chancellor <nathan@kernel.org> Reviewed-by: Linus Walleij <linus.walleij@linaro.org> Cc: "Russell King (Oracle)" <rmk+kernel@armlinux.org.uk> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Andrew Davis <afd@ti.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Eric DeVolder <eric.devolder@oracle.com> Cc: Rob Herring <robh@kernel.org> Cc: <linux-arm-kernel@lists.infradead.org>
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@ -34,6 +34,7 @@ config ARM
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select ARCH_MIGHT_HAVE_PC_PARPORT
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select ARCH_OPTIONAL_KERNEL_RWX if ARCH_HAS_STRICT_KERNEL_RWX
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select ARCH_OPTIONAL_KERNEL_RWX_DEFAULT if CPU_V7
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select ARCH_NEED_CMPXCHG_1_EMU if CPU_V6
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select ARCH_SUPPORTS_ATOMIC_RMW
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select ARCH_SUPPORTS_CFI_CLANG
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select ARCH_SUPPORTS_HUGETLBFS if ARM_LPAE
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@ -5,6 +5,7 @@
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#include <linux/irqflags.h>
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#include <linux/prefetch.h>
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#include <asm/barrier.h>
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#include <linux/cmpxchg-emu.h>
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#if defined(CONFIG_CPU_SA1100) || defined(CONFIG_CPU_SA110)
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/*
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@ -162,7 +163,11 @@ static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old,
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prefetchw((const void *)ptr);
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switch (size) {
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#ifndef CONFIG_CPU_V6 /* min ARCH >= ARMv6K */
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#ifdef CONFIG_CPU_V6 /* ARCH == ARMv6 */
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case 1:
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oldval = cmpxchg_emu_u8((volatile u8 *)ptr, old, new);
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break;
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#else /* min ARCH > ARMv6 */
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case 1:
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do {
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asm volatile("@ __cmpxchg1\n"
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