[PATCH v2 13/20] arm64: cmpxchg_dbl: patch in lse instructions when supported by the CPU
Will Deacon
will.deacon at arm.com
Fri Jul 24 03:42:04 PDT 2015
On CPUs which support the LSE atomic instructions introduced in ARMv8.1,
it makes sense to use them in preference to ll/sc sequences.
This patch introduces runtime patching of our cmpxchg_double primitives
so that the LSE casp instruction is used instead.
Signed-off-by: Will Deacon <will.deacon at arm.com>
---
arch/arm64/include/asm/atomic_ll_sc.h | 34 ++++++++++++++++++
arch/arm64/include/asm/atomic_lse.h | 43 ++++++++++++++++++++++
arch/arm64/include/asm/cmpxchg.h | 68 +++++++++--------------------------
3 files changed, 94 insertions(+), 51 deletions(-)
diff --git a/arch/arm64/include/asm/atomic_ll_sc.h b/arch/arm64/include/asm/atomic_ll_sc.h
index b4298f9a898f..77d3aabf52ad 100644
--- a/arch/arm64/include/asm/atomic_ll_sc.h
+++ b/arch/arm64/include/asm/atomic_ll_sc.h
@@ -243,4 +243,38 @@ __CMPXCHG_CASE( , , mb_8, dmb ish, "memory")
#undef __CMPXCHG_CASE
+#define __CMPXCHG_DBL(name, mb, cl) \
+__LL_SC_INLINE int \
+__LL_SC_PREFIX(__cmpxchg_double##name(unsigned long old1, \
+ unsigned long old2, \
+ unsigned long new1, \
+ unsigned long new2, \
+ volatile void *ptr)) \
+{ \
+ unsigned long tmp, ret; \
+ \
+ asm volatile("// __cmpxchg_double" #name "\n" \
+ " " #mb "\n" \
+ "1: ldxp %0, %1, %2\n" \
+ " eor %0, %0, %3\n" \
+ " eor %1, %1, %4\n" \
+ " orr %1, %0, %1\n" \
+ " cbnz %1, 2f\n" \
+ " stxp %w0, %5, %6, %2\n" \
+ " cbnz %w0, 1b\n" \
+ " " #mb "\n" \
+ "2:" \
+ : "=&r" (tmp), "=&r" (ret), "+Q" (*(unsigned long *)ptr) \
+ : "r" (old1), "r" (old2), "r" (new1), "r" (new2) \
+ : cl); \
+ \
+ return ret; \
+} \
+__LL_SC_EXPORT(__cmpxchg_double##name);
+
+__CMPXCHG_DBL( , , )
+__CMPXCHG_DBL(_mb, dmb ish, "memory")
+
+#undef __CMPXCHG_DBL
+
#endif /* __ASM_ATOMIC_LL_SC_H */
diff --git a/arch/arm64/include/asm/atomic_lse.h b/arch/arm64/include/asm/atomic_lse.h
index 5136c3ab48e9..db41a63691cd 100644
--- a/arch/arm64/include/asm/atomic_lse.h
+++ b/arch/arm64/include/asm/atomic_lse.h
@@ -282,4 +282,47 @@ __CMPXCHG_CASE(x, , mb_8, al, "memory")
#undef __LL_SC_CMPXCHG
#undef __CMPXCHG_CASE
+#define __LL_SC_CMPXCHG_DBL(op) __LL_SC_CALL(__cmpxchg_double##op)
+
+#define __CMPXCHG_DBL(name, mb, cl...) \
+static inline int __cmpxchg_double##name(unsigned long old1, \
+ unsigned long old2, \
+ unsigned long new1, \
+ unsigned long new2, \
+ volatile void *ptr) \
+{ \
+ unsigned long oldval1 = old1; \
+ unsigned long oldval2 = old2; \
+ register unsigned long x0 asm ("x0") = old1; \
+ register unsigned long x1 asm ("x1") = old2; \
+ register unsigned long x2 asm ("x2") = new1; \
+ register unsigned long x3 asm ("x3") = new2; \
+ register unsigned long x4 asm ("x4") = (unsigned long)ptr; \
+ \
+ asm volatile(ARM64_LSE_ATOMIC_INSN( \
+ /* LL/SC */ \
+ " nop\n" \
+ " nop\n" \
+ " nop\n" \
+ __LL_SC_CMPXCHG_DBL(name), \
+ /* LSE atomics */ \
+ " casp" #mb "\t%[old1], %[old2], %[new1], %[new2], %[v]\n"\
+ " eor %[old1], %[old1], %[oldval1]\n" \
+ " eor %[old2], %[old2], %[oldval2]\n" \
+ " orr %[old1], %[old1], %[old2]") \
+ : [old1] "+r" (x0), [old2] "+r" (x1), \
+ [v] "+Q" (*(unsigned long *)ptr) \
+ : [new1] "r" (x2), [new2] "r" (x3), [ptr] "r" (x4), \
+ [oldval1] "r" (oldval1), [oldval2] "r" (oldval2) \
+ : "x30" , ##cl); \
+ \
+ return x0; \
+}
+
+__CMPXCHG_DBL( , )
+__CMPXCHG_DBL(_mb, al, "memory")
+
+#undef __LL_SC_CMPXCHG_DBL
+#undef __CMPXCHG_DBL
+
#endif /* __ASM_ATOMIC_LSE_H */
diff --git a/arch/arm64/include/asm/cmpxchg.h b/arch/arm64/include/asm/cmpxchg.h
index 60a558127cef..f70212629d02 100644
--- a/arch/arm64/include/asm/cmpxchg.h
+++ b/arch/arm64/include/asm/cmpxchg.h
@@ -128,51 +128,6 @@ static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old,
unreachable();
}
-#define system_has_cmpxchg_double() 1
-
-static inline int __cmpxchg_double(volatile void *ptr1, volatile void *ptr2,
- unsigned long old1, unsigned long old2,
- unsigned long new1, unsigned long new2, int size)
-{
- unsigned long loop, lost;
-
- switch (size) {
- case 8:
- VM_BUG_ON((unsigned long *)ptr2 - (unsigned long *)ptr1 != 1);
- do {
- asm volatile("// __cmpxchg_double8\n"
- " ldxp %0, %1, %2\n"
- " eor %0, %0, %3\n"
- " eor %1, %1, %4\n"
- " orr %1, %0, %1\n"
- " mov %w0, #0\n"
- " cbnz %1, 1f\n"
- " stxp %w0, %5, %6, %2\n"
- "1:\n"
- : "=&r"(loop), "=&r"(lost), "+Q" (*(u64 *)ptr1)
- : "r" (old1), "r"(old2), "r"(new1), "r"(new2));
- } while (loop);
- break;
- default:
- BUILD_BUG();
- }
-
- return !lost;
-}
-
-static inline int __cmpxchg_double_mb(volatile void *ptr1, volatile void *ptr2,
- unsigned long old1, unsigned long old2,
- unsigned long new1, unsigned long new2, int size)
-{
- int ret;
-
- smp_mb();
- ret = __cmpxchg_double(ptr1, ptr2, old1, old2, new1, new2, size);
- smp_mb();
-
- return ret;
-}
-
static inline unsigned long __cmpxchg_mb(volatile void *ptr, unsigned long old,
unsigned long new, int size)
{
@@ -210,21 +165,32 @@ static inline unsigned long __cmpxchg_mb(volatile void *ptr, unsigned long old,
__ret; \
})
+#define system_has_cmpxchg_double() 1
+
+#define __cmpxchg_double_check(ptr1, ptr2) \
+({ \
+ if (sizeof(*(ptr1)) != 8) \
+ BUILD_BUG(); \
+ VM_BUG_ON((unsigned long *)(ptr2) - (unsigned long *)(ptr1) != 1); \
+})
+
#define cmpxchg_double(ptr1, ptr2, o1, o2, n1, n2) \
({\
int __ret;\
- __ret = __cmpxchg_double_mb((ptr1), (ptr2), (unsigned long)(o1), \
- (unsigned long)(o2), (unsigned long)(n1), \
- (unsigned long)(n2), sizeof(*(ptr1)));\
+ __cmpxchg_double_check(ptr1, ptr2); \
+ __ret = !__cmpxchg_double_mb((unsigned long)(o1), (unsigned long)(o2), \
+ (unsigned long)(n1), (unsigned long)(n2), \
+ ptr1); \
__ret; \
})
#define cmpxchg_double_local(ptr1, ptr2, o1, o2, n1, n2) \
({\
int __ret;\
- __ret = __cmpxchg_double((ptr1), (ptr2), (unsigned long)(o1), \
- (unsigned long)(o2), (unsigned long)(n1), \
- (unsigned long)(n2), sizeof(*(ptr1)));\
+ __cmpxchg_double_check(ptr1, ptr2); \
+ __ret = !__cmpxchg_double((unsigned long)(o1), (unsigned long)(o2), \
+ (unsigned long)(n1), (unsigned long)(n2), \
+ ptr1); \
__ret; \
})
--
2.1.4
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