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

Sebastian Andrzej Siewior
2019-10-13T22:14:22Z

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 <sebastian@breakpoint.cc>
---
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