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-rw-r--r--arch/arm/include/asm/cmpxchg.h295
1 files changed, 295 insertions, 0 deletions
diff --git a/arch/arm/include/asm/cmpxchg.h b/arch/arm/include/asm/cmpxchg.h
new file mode 100644
index 00000000000..d41d7cbf0ad
--- /dev/null
+++ b/arch/arm/include/asm/cmpxchg.h
@@ -0,0 +1,295 @@
+#ifndef __ASM_ARM_CMPXCHG_H
+#define __ASM_ARM_CMPXCHG_H
+
+#include <linux/irqflags.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
+
+ smp_mb();
+
+ switch (size) {
+#if __LINUX_ARM_ARCH__ >= 6
+ 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 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:
+ __bad_xchg(ptr, size), ret = 0;
+ break;
+ }
+ smp_mb();
+
+ return ret;
+}
+
+#define xchg(ptr,x) \
+ ((__typeof__(*(ptr)))__xchg((unsigned long)(x),(ptr),sizeof(*(ptr))))
+
+#include <asm-generic/cmpxchg-local.h>
+
+#if __LINUX_ARM_ARCH__ < 6
+/* min ARCH < ARMv6 */
+
+#ifdef CONFIG_SMP
+#error "SMP is not supported on this platform"
+#endif
+
+/*
+ * cmpxchg_local and cmpxchg64_local are atomic wrt current CPU. Always make
+ * them available.
+ */
+#define cmpxchg_local(ptr, o, n) \
+ ((__typeof__(*(ptr)))__cmpxchg_local_generic((ptr), (unsigned long)(o),\
+ (unsigned long)(n), sizeof(*(ptr))))
+#define cmpxchg64_local(ptr, o, n) __cmpxchg64_local_generic((ptr), (o), (n))
+
+#ifndef CONFIG_SMP
+#include <asm-generic/cmpxchg.h>
+#endif
+
+#else /* min ARCH >= ARMv6 */
+
+extern void __bad_cmpxchg(volatile void *ptr, int size);
+
+/*
+ * cmpxchg only support 32-bits operands on ARMv6.
+ */
+
+static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old,
+ unsigned long new, int size)
+{
+ unsigned long oldval, res;
+
+ switch (size) {
+#ifndef CONFIG_CPU_V6 /* min ARCH >= ARMv6K */
+ case 1:
+ do {
+ asm volatile("@ __cmpxchg1\n"
+ " ldrexb %1, [%2]\n"
+ " mov %0, #0\n"
+ " teq %1, %3\n"
+ " strexbeq %0, %4, [%2]\n"
+ : "=&r" (res), "=&r" (oldval)
+ : "r" (ptr), "Ir" (old), "r" (new)
+ : "memory", "cc");
+ } while (res);
+ break;
+ case 2:
+ do {
+ asm volatile("@ __cmpxchg1\n"
+ " ldrexh %1, [%2]\n"
+ " mov %0, #0\n"
+ " teq %1, %3\n"
+ " strexheq %0, %4, [%2]\n"
+ : "=&r" (res), "=&r" (oldval)
+ : "r" (ptr), "Ir" (old), "r" (new)
+ : "memory", "cc");
+ } while (res);
+ break;
+#endif
+ case 4:
+ do {
+ asm volatile("@ __cmpxchg4\n"
+ " ldrex %1, [%2]\n"
+ " mov %0, #0\n"
+ " teq %1, %3\n"
+ " strexeq %0, %4, [%2]\n"
+ : "=&r" (res), "=&r" (oldval)
+ : "r" (ptr), "Ir" (old), "r" (new)
+ : "memory", "cc");
+ } while (res);
+ break;
+ default:
+ __bad_cmpxchg(ptr, size);
+ oldval = 0;
+ }
+
+ return oldval;
+}
+
+static inline unsigned long __cmpxchg_mb(volatile void *ptr, unsigned long old,
+ unsigned long new, int size)
+{
+ unsigned long ret;
+
+ smp_mb();
+ ret = __cmpxchg(ptr, old, new, size);
+ smp_mb();
+
+ return ret;
+}
+
+#define cmpxchg(ptr,o,n) \
+ ((__typeof__(*(ptr)))__cmpxchg_mb((ptr), \
+ (unsigned long)(o), \
+ (unsigned long)(n), \
+ sizeof(*(ptr))))
+
+static inline unsigned long __cmpxchg_local(volatile void *ptr,
+ unsigned long old,
+ unsigned long new, int size)
+{
+ unsigned long ret;
+
+ switch (size) {
+#ifdef CONFIG_CPU_V6 /* min ARCH == ARMv6 */
+ case 1:
+ case 2:
+ ret = __cmpxchg_local_generic(ptr, old, new, size);
+ break;
+#endif
+ default:
+ ret = __cmpxchg(ptr, old, new, size);
+ }
+
+ return ret;
+}
+
+#define cmpxchg_local(ptr,o,n) \
+ ((__typeof__(*(ptr)))__cmpxchg_local((ptr), \
+ (unsigned long)(o), \
+ (unsigned long)(n), \
+ sizeof(*(ptr))))
+
+#ifndef CONFIG_CPU_V6 /* min ARCH >= ARMv6K */
+
+/*
+ * Note : ARMv7-M (currently unsupported by Linux) does not support
+ * ldrexd/strexd. If ARMv7-M is ever supported by the Linux kernel, it should
+ * not be allowed to use __cmpxchg64.
+ */
+static inline unsigned long long __cmpxchg64(volatile void *ptr,
+ unsigned long long old,
+ unsigned long long new)
+{
+ register unsigned long long oldval asm("r0");
+ register unsigned long long __old asm("r2") = old;
+ register unsigned long long __new asm("r4") = new;
+ unsigned long res;
+
+ do {
+ asm volatile(
+ " @ __cmpxchg8\n"
+ " ldrexd %1, %H1, [%2]\n"
+ " mov %0, #0\n"
+ " teq %1, %3\n"
+ " teqeq %H1, %H3\n"
+ " strexdeq %0, %4, %H4, [%2]\n"
+ : "=&r" (res), "=&r" (oldval)
+ : "r" (ptr), "Ir" (__old), "r" (__new)
+ : "memory", "cc");
+ } while (res);
+
+ return oldval;
+}
+
+static inline unsigned long long __cmpxchg64_mb(volatile void *ptr,
+ unsigned long long old,
+ unsigned long long new)
+{
+ unsigned long long ret;
+
+ smp_mb();
+ ret = __cmpxchg64(ptr, old, new);
+ smp_mb();
+
+ return ret;
+}
+
+#define cmpxchg64(ptr,o,n) \
+ ((__typeof__(*(ptr)))__cmpxchg64_mb((ptr), \
+ (unsigned long long)(o), \
+ (unsigned long long)(n)))
+
+#define cmpxchg64_local(ptr,o,n) \
+ ((__typeof__(*(ptr)))__cmpxchg64((ptr), \
+ (unsigned long long)(o), \
+ (unsigned long long)(n)))
+
+#else /* min ARCH = ARMv6 */
+
+#define cmpxchg64_local(ptr, o, n) __cmpxchg64_local_generic((ptr), (o), (n))
+
+#endif
+
+#endif /* __LINUX_ARM_ARCH__ >= 6 */
+
+#endif /* __ASM_ARM_CMPXCHG_H */
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