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authorWill Deacon <will.deacon@arm.com>2011-04-08 13:58:39 +0100
committerNicolas Pitre <nicolas.pitre@linaro.org>2011-04-25 14:42:14 -0400
commit1d60a2699fd1340a149cf30b00ac30c233a4a553 (patch)
tree54c362feb32b012690077b850f8f38eefe6221a6
parent7286150b85b4e08a7b4667c41f5fef56130da43a (diff)
ARM: futex: add SMP futex support when !CPU_USE_DOMAINS
This patch uses the load/store exclusive instructions to add SMP futex support for ARM. Since the ARM architecture does not provide instructions for unprivileged exclusive memory accesses, we can only provide SMP futexes when CPU domain support is disabled. Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Nicolas Pitre <nicolas.pitre@linaro.org>
-rw-r--r--arch/arm/include/asm/futex.h137
1 files changed, 90 insertions, 47 deletions
diff --git a/arch/arm/include/asm/futex.h b/arch/arm/include/asm/futex.h
index 199a6b6de7f..8c73900da9e 100644
--- a/arch/arm/include/asm/futex.h
+++ b/arch/arm/include/asm/futex.h
@@ -3,16 +3,74 @@
#ifdef __KERNEL__
+#if defined(CONFIG_CPU_USE_DOMAINS) && defined(CONFIG_SMP)
+/* ARM doesn't provide unprivileged exclusive memory accessors */
+#include <asm-generic/futex.h>
+#else
+
+#include <linux/futex.h>
+#include <linux/uaccess.h>
+#include <asm/errno.h>
+
+#define __futex_atomic_ex_table(err_reg) \
+ "3:\n" \
+ " .pushsection __ex_table,\"a\"\n" \
+ " .align 3\n" \
+ " .long 1b, 4f, 2b, 4f\n" \
+ " .popsection\n" \
+ " .pushsection .fixup,\"ax\"\n" \
+ "4: mov %0, " err_reg "\n" \
+ " b 3b\n" \
+ " .popsection"
+
#ifdef CONFIG_SMP
-#include <asm-generic/futex.h>
+#define __futex_atomic_op(insn, ret, oldval, uaddr, oparg) \
+ smp_mb(); \
+ __asm__ __volatile__( \
+ "1: ldrex %1, [%2]\n" \
+ " " insn "\n" \
+ "2: strex %1, %0, [%2]\n" \
+ " teq %1, #0\n" \
+ " bne 1b\n" \
+ " mov %0, #0\n" \
+ __futex_atomic_ex_table("%4") \
+ : "=&r" (ret), "=&r" (oldval) \
+ : "r" (uaddr), "r" (oparg), "Ir" (-EFAULT) \
+ : "cc", "memory")
+
+static inline int
+futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
+ u32 oldval, u32 newval)
+{
+ int ret;
+ u32 val;
+
+ if (!access_ok(VERIFY_WRITE, uaddr, sizeof(u32)))
+ return -EFAULT;
+
+ smp_mb();
+ __asm__ __volatile__("@futex_atomic_cmpxchg_inatomic\n"
+ "1: ldrex %1, [%4]\n"
+ " teq %1, %2\n"
+ " ite eq @ explicit IT needed for the 2b label\n"
+ "2: strexeq %0, %3, [%4]\n"
+ " movne %0, #0\n"
+ " teq %0, #0\n"
+ " bne 1b\n"
+ __futex_atomic_ex_table("%5")
+ : "=&r" (ret), "=&r" (val)
+ : "r" (oldval), "r" (newval), "r" (uaddr), "Ir" (-EFAULT)
+ : "cc", "memory");
+ smp_mb();
+
+ *uval = val;
+ return ret;
+}
#else /* !SMP, we can work around lack of atomic ops by disabling preemption */
-#include <linux/futex.h>
#include <linux/preempt.h>
-#include <linux/uaccess.h>
-#include <asm/errno.h>
#include <asm/domain.h>
#define __futex_atomic_op(insn, ret, oldval, uaddr, oparg) \
@@ -21,20 +79,38 @@
" " insn "\n" \
"2: " T(str) " %0, [%2]\n" \
" mov %0, #0\n" \
- "3:\n" \
- " .pushsection __ex_table,\"a\"\n" \
- " .align 3\n" \
- " .long 1b, 4f, 2b, 4f\n" \
- " .popsection\n" \
- " .pushsection .fixup,\"ax\"\n" \
- "4: mov %0, %4\n" \
- " b 3b\n" \
- " .popsection" \
+ __futex_atomic_ex_table("%4") \
: "=&r" (ret), "=&r" (oldval) \
: "r" (uaddr), "r" (oparg), "Ir" (-EFAULT) \
: "cc", "memory")
static inline int
+futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
+ u32 oldval, u32 newval)
+{
+ int ret = 0;
+ u32 val;
+
+ if (!access_ok(VERIFY_WRITE, uaddr, sizeof(u32)))
+ return -EFAULT;
+
+ __asm__ __volatile__("@futex_atomic_cmpxchg_inatomic\n"
+ "1: " T(ldr) " %1, [%4]\n"
+ " teq %1, %2\n"
+ " it eq @ explicit IT needed for the 2b label\n"
+ "2: " T(streq) " %3, [%4]\n"
+ __futex_atomic_ex_table("%5")
+ : "+r" (ret), "=&r" (val)
+ : "r" (oldval), "r" (newval), "r" (uaddr), "Ir" (-EFAULT)
+ : "cc", "memory");
+
+ *uval = val;
+ return ret;
+}
+
+#endif /* !SMP */
+
+static inline int
futex_atomic_op_inuser (int encoded_op, u32 __user *uaddr)
{
int op = (encoded_op >> 28) & 7;
@@ -87,39 +163,6 @@ futex_atomic_op_inuser (int encoded_op, u32 __user *uaddr)
return ret;
}
-static inline int
-futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
- u32 oldval, u32 newval)
-{
- int ret = 0;
- u32 val;
-
- if (!access_ok(VERIFY_WRITE, uaddr, sizeof(u32)))
- return -EFAULT;
-
- __asm__ __volatile__("@futex_atomic_cmpxchg_inatomic\n"
- "1: " T(ldr) " %1, [%4]\n"
- " teq %1, %2\n"
- " it eq @ explicit IT needed for the 2b label\n"
- "2: " T(streq) " %3, [%4]\n"
- "3:\n"
- " .pushsection __ex_table,\"a\"\n"
- " .align 3\n"
- " .long 1b, 4f, 2b, 4f\n"
- " .popsection\n"
- " .pushsection .fixup,\"ax\"\n"
- "4: mov %0, %5\n"
- " b 3b\n"
- " .popsection"
- : "+r" (ret), "=&r" (val)
- : "r" (oldval), "r" (newval), "r" (uaddr), "Ir" (-EFAULT)
- : "cc", "memory");
-
- *uval = val;
- return ret;
-}
-
-#endif /* !SMP */
-
+#endif /* !(CPU_USE_DOMAINS && SMP) */
#endif /* __KERNEL__ */
#endif /* _ASM_ARM_FUTEX_H */