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authorLey Foon Tan <lftan@altera.com>2014-11-06 15:19:34 +0800
committerLey Foon Tan <lftan@altera.com>2014-12-08 12:55:48 +0800
commit00f634bc522dedc8418fb6d967a76cc4c10376a5 (patch)
tree693a2b613bdbb2c6ed9401e8fd261548dc5bd538
parentb2776bf7149bddd1f4161f14f79520f17fc1d71d (diff)
asm-generic: add generic futex for !CONFIG_SMP
Follow m68k futex implementation for !CONFIG_SMP. Signed-off-by: Ley Foon Tan <lftan@altera.com> Acked-by: Arnd Bergmann <arnd@arndb.de>
-rw-r--r--include/asm-generic/futex.h114
1 files changed, 114 insertions, 0 deletions
diff --git a/include/asm-generic/futex.h b/include/asm-generic/futex.h
index 01f227e1425..b59b5a52637 100644
--- a/include/asm-generic/futex.h
+++ b/include/asm-generic/futex.h
@@ -5,6 +5,119 @@
#include <linux/uaccess.h>
#include <asm/errno.h>
+#ifndef CONFIG_SMP
+/*
+ * The following implementation only for uniprocessor machines.
+ * For UP, it's relies on the fact that pagefault_disable() also disables
+ * preemption to ensure mutual exclusion.
+ *
+ */
+
+/**
+ * futex_atomic_op_inuser() - Atomic arithmetic operation with constant
+ * argument and comparison of the previous
+ * futex value with another constant.
+ *
+ * @encoded_op: encoded operation to execute
+ * @uaddr: pointer to user space address
+ *
+ * Return:
+ * 0 - On success
+ * <0 - On error
+ */
+static inline int
+futex_atomic_op_inuser(int encoded_op, u32 __user *uaddr)
+{
+ int op = (encoded_op >> 28) & 7;
+ int cmp = (encoded_op >> 24) & 15;
+ int oparg = (encoded_op << 8) >> 20;
+ int cmparg = (encoded_op << 20) >> 20;
+ int oldval, ret;
+ u32 tmp;
+
+ if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28))
+ oparg = 1 << oparg;
+
+ pagefault_disable();
+
+ ret = -EFAULT;
+ if (unlikely(get_user(oldval, uaddr) != 0))
+ goto out_pagefault_enable;
+
+ ret = 0;
+ tmp = oldval;
+
+ switch (op) {
+ case FUTEX_OP_SET:
+ tmp = oparg;
+ break;
+ case FUTEX_OP_ADD:
+ tmp += oparg;
+ break;
+ case FUTEX_OP_OR:
+ tmp |= oparg;
+ break;
+ case FUTEX_OP_ANDN:
+ tmp &= ~oparg;
+ break;
+ case FUTEX_OP_XOR:
+ tmp ^= oparg;
+ break;
+ default:
+ ret = -ENOSYS;
+ }
+
+ if (ret == 0 && unlikely(put_user(tmp, uaddr) != 0))
+ ret = -EFAULT;
+
+out_pagefault_enable:
+ pagefault_enable();
+
+ if (ret == 0) {
+ switch (cmp) {
+ case FUTEX_OP_CMP_EQ: ret = (oldval == cmparg); break;
+ case FUTEX_OP_CMP_NE: ret = (oldval != cmparg); break;
+ case FUTEX_OP_CMP_LT: ret = (oldval < cmparg); break;
+ case FUTEX_OP_CMP_GE: ret = (oldval >= cmparg); break;
+ case FUTEX_OP_CMP_LE: ret = (oldval <= cmparg); break;
+ case FUTEX_OP_CMP_GT: ret = (oldval > cmparg); break;
+ default: ret = -ENOSYS;
+ }
+ }
+ return ret;
+}
+
+/**
+ * futex_atomic_cmpxchg_inatomic() - Compare and exchange the content of the
+ * uaddr with newval if the current value is
+ * oldval.
+ * @uval: pointer to store content of @uaddr
+ * @uaddr: pointer to user space address
+ * @oldval: old value
+ * @newval: new value to store to @uaddr
+ *
+ * Return:
+ * 0 - On success
+ * <0 - On error
+ */
+static inline int
+futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
+ u32 oldval, u32 newval)
+{
+ u32 val;
+
+ if (unlikely(get_user(val, uaddr) != 0))
+ return -EFAULT;
+
+ if (val == oldval && unlikely(put_user(newval, uaddr) != 0))
+ return -EFAULT;
+
+ *uval = val;
+
+ return 0;
+}
+
+#else
static inline int
futex_atomic_op_inuser (int encoded_op, u32 __user *uaddr)
{
@@ -54,4 +167,5 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
return -ENOSYS;
}
+#endif /* CONFIG_SMP */
#endif