Subject: [PATCH 2/6] ARM: cmpxchg: Define first cmpxchg() followed by xchg()

From: Sebastian Andrzej Siewior <[email-masked]>
Date: Mon, 14 Oct 2019 00:13:06 +0200

In order to use the generic xchg_() implementation based on cmpxchg()
we need cmpxchg defined first.
Move the xchg bits to the lower part of the file.

Signed-off-by: Sebastian Andrzej Siewior <[email-masked]>
---
 arch/arm/include/asm/cmpxchg.h | 227 ++++++++++++++++-----------------
 1 file changed, 113 insertions(+), 114 deletions(-)

diff --git a/arch/arm/include/asm/cmpxchg.h b/arch/arm/include/asm/cmpxchg.h
index 8b701f8e175c0..c61de6acf41ed 100644
--- a/arch/arm/include/asm/cmpxchg.h
+++ b/arch/arm/include/asm/cmpxchg.h
@@ -5,120 +5,6 @@
 #include <linux/irqflags.h>
 #include <linux/prefetch.h>
 #include <asm/barrier.h>
-
-#if defined(CONFIG_CPU_SA1100) || defined(CONFIG_CPU_SA110)
-/*
- * On the StrongARM, "swp" is terminally broken since it bypasses the
- * cache totally.  This means that the cache becomes inconsistent, and,
- * since we use normal loads/stores as well, this is really bad.
- * Typically, this causes oopsen in filp_close, but could have other,
- * more disastrous effects.  There are two work-arounds:
- *  1. Disable interrupts and emulate the atomic swap
- *  2. Clean the cache, perform atomic swap, flush the cache
- *
- * We choose (1) since its the "easiest" to achieve here and is not
- * dependent on the processor type.
- *
- * NOTE that this solution won't work on an SMP system, so explcitly
- * forbid it here.
- */
-#define swp_is_buggy
-#endif
-
-static inline unsigned long __xchg(unsigned long x, volatile void *ptr, int size)
-{
-	extern void __bad_xchg(volatile void *, int);
-	unsigned long ret;
-#ifdef swp_is_buggy
-	unsigned long flags;
-#endif
-#if __LINUX_ARM_ARCH__ >= 6
-	unsigned int tmp;
-#endif
-
-	prefetchw((const void *)ptr);
-
-	switch (size) {
-#if __LINUX_ARM_ARCH__ >= 6
-#ifndef CONFIG_CPU_V6 /* MIN ARCH >= V6K */
-	case 1:
-		asm volatile("@	__xchg1\n"
-		"1:	ldrexb	%0, [%3]\n"
-		"	strexb	%1, %2, [%3]\n"
-		"	teq	%1, #0\n"
-		"	bne	1b"
-			: "=&r" (ret), "=&r" (tmp)
-			: "r" (x), "r" (ptr)
-			: "memory", "cc");
-		break;
-	case 2:
-		asm volatile("@	__xchg2\n"
-		"1:	ldrexh	%0, [%3]\n"
-		"	strexh	%1, %2, [%3]\n"
-		"	teq	%1, #0\n"
-		"	bne	1b"
-			: "=&r" (ret), "=&r" (tmp)
-			: "r" (x), "r" (ptr)
-			: "memory", "cc");
-		break;
-#endif
-	case 4:
-		asm volatile("@	__xchg4\n"
-		"1:	ldrex	%0, [%3]\n"
-		"	strex	%1, %2, [%3]\n"
-		"	teq	%1, #0\n"
-		"	bne	1b"
-			: "=&r" (ret), "=&r" (tmp)
-			: "r" (x), "r" (ptr)
-			: "memory", "cc");
-		break;
-#elif defined(swp_is_buggy)
-#ifdef CONFIG_SMP
-#error SMP is not supported on this platform
-#endif
-	case 1:
-		raw_local_irq_save(flags);
-		ret = *(volatile unsigned char *)ptr;
-		*(volatile unsigned char *)ptr = x;
-		raw_local_irq_restore(flags);
-		break;
-
-	case 4:
-		raw_local_irq_save(flags);
-		ret = *(volatile unsigned long *)ptr;
-		*(volatile unsigned long *)ptr = x;
-		raw_local_irq_restore(flags);
-		break;
-#else
-	case 1:
-		asm volatile("@	__xchg1\n"
-		"	swpb	%0, %1, [%2]"
-			: "=&r" (ret)
-			: "r" (x), "r" (ptr)
-			: "memory", "cc");
-		break;
-	case 4:
-		asm volatile("@	__xchg4\n"
-		"	swp	%0, %1, [%2]"
-			: "=&r" (ret)
-			: "r" (x), "r" (ptr)
-			: "memory", "cc");
-		break;
-#endif
-	default:
-		/* Cause a link-time error, the xchg() size is not supported */
-		__bad_xchg(ptr, size), ret = 0;
-		break;
-	}
-
-	return ret;
-}
-
-#define xchg_relaxed(ptr, x) ({						\
-	(__typeof__(*(ptr)))__xchg((unsigned long)(x), (ptr),		\
-				   sizeof(*(ptr)));			\
-})
-
 #include <asm-generic/cmpxchg-local.h>
 
 #if __LINUX_ARM_ARCH__ < 6
@@ -276,4 +162,117 @@ static inline unsigned long long __cmpxchg64(unsigned long long *ptr,
 
 #endif	/* __LINUX_ARM_ARCH__ >= 6 */
 
+#if defined(CONFIG_CPU_SA1100) || defined(CONFIG_CPU_SA110)
+/*
+ * On the StrongARM, "swp" is terminally broken since it bypasses the
+ * cache totally.  This means that the cache becomes inconsistent, and,
+ * since we use normal loads/stores as well, this is really bad.
+ * Typically, this causes oopsen in filp_close, but could have other,
+ * more disastrous effects.  There are two work-arounds:
+ *  1. Disable interrupts and emulate the atomic swap
+ *  2. Clean the cache, perform atomic swap, flush the cache
+ *
+ * We choose (1) since its the "easiest" to achieve here and is not
+ * dependent on the processor type.
+ *
+ * NOTE that this solution won't work on an SMP system, so explcitly
+ * forbid it here.
+ */
+#define swp_is_buggy
+#endif
+
+static inline unsigned long __xchg(unsigned long x, volatile void *ptr, int size)
+{
+	extern void __bad_xchg(volatile void *, int);
+	unsigned long ret;
+#ifdef swp_is_buggy
+	unsigned long flags;
+#endif
+#if __LINUX_ARM_ARCH__ >= 6
+	unsigned int tmp;
+#endif
+
+	prefetchw((const void *)ptr);
+
+	switch (size) {
+#if __LINUX_ARM_ARCH__ >= 6
+#ifndef CONFIG_CPU_V6 /* MIN ARCH >= V6K */
+	case 1:
+		asm volatile("@	__xchg1\n"
+		"1:	ldrexb	%0, [%3]\n"
+		"	strexb	%1, %2, [%3]\n"
+		"	teq	%1, #0\n"
+		"	bne	1b"
+			: "=&r" (ret), "=&r" (tmp)
+			: "r" (x), "r" (ptr)
+			: "memory", "cc");
+		break;
+	case 2:
+		asm volatile("@	__xchg2\n"
+		"1:	ldrexh	%0, [%3]\n"
+		"	strexh	%1, %2, [%3]\n"
+		"	teq	%1, #0\n"
+		"	bne	1b"
+			: "=&r" (ret), "=&r" (tmp)
+			: "r" (x), "r" (ptr)
+			: "memory", "cc");
+		break;
+#endif
+	case 4:
+		asm volatile("@	__xchg4\n"
+		"1:	ldrex	%0, [%3]\n"
+		"	strex	%1, %2, [%3]\n"
+		"	teq	%1, #0\n"
+		"	bne	1b"
+			: "=&r" (ret), "=&r" (tmp)
+			: "r" (x), "r" (ptr)
+			: "memory", "cc");
+		break;
+#elif defined(swp_is_buggy)
+#ifdef CONFIG_SMP
+#error SMP is not supported on this platform
+#endif
+	case 1:
+		raw_local_irq_save(flags);
+		ret = *(volatile unsigned char *)ptr;
+		*(volatile unsigned char *)ptr = x;
+		raw_local_irq_restore(flags);
+		break;
+
+	case 4:
+		raw_local_irq_save(flags);
+		ret = *(volatile unsigned long *)ptr;
+		*(volatile unsigned long *)ptr = x;
+		raw_local_irq_restore(flags);
+		break;
+#else
+	case 1:
+		asm volatile("@	__xchg1\n"
+		"	swpb	%0, %1, [%2]"
+			: "=&r" (ret)
+			: "r" (x), "r" (ptr)
+			: "memory", "cc");
+		break;
+	case 4:
+		asm volatile("@	__xchg4\n"
+		"	swp	%0, %1, [%2]"
+			: "=&r" (ret)
+			: "r" (x), "r" (ptr)
+			: "memory", "cc");
+		break;
+#endif
+	default:
+		/* Cause a link-time error, the xchg() size is not supported */
+		__bad_xchg(ptr, size), ret = 0;
+		break;
+	}
+
+	return ret;
+}
+
+#define xchg_relaxed(ptr, x) ({						\
+	(__typeof__(*(ptr)))__xchg((unsigned long)(x), (ptr),		\
+				   sizeof(*(ptr)));			\
+})
+
 #endif /* __ASM_ARM_CMPXCHG_H */
-- 
2.23.0

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