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authorWill Deacon <will.deacon@arm.com>2011-04-28 19:43:01 +0200
committerRussell King <rmk+kernel@arm.linux.org.uk>2011-05-12 11:11:44 +0200
commitc1b0db56604b4ccc55a325104b14093aeedeb829 (patch)
tree3c7a8df020dc52fa87ce013cfad42df3dea5f312 /arch/arm/include/asm/futex.h
parentARM: 6859/1: Add writethrough dcache support for ARM926EJS processor (diff)
downloadlinux-c1b0db56604b4ccc55a325104b14093aeedeb829.tar.xz
linux-c1b0db56604b4ccc55a325104b14093aeedeb829.zip
ARM: 6889/1: 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. Cc: Nicolas Pitre <nico@fluxnic.net> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Diffstat (limited to 'arch/arm/include/asm/futex.h')
-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 199a6b6de7f4..8c73900da9ed 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 */