linux-kernel - [PATCH v6 01/29] asm-generic: add generic futex for !CONFIG

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Message-ID: <1415011945-3297-2-git-send-email-lftan@altera.com>
Date:	Mon, 3 Nov 2014 18:51:57 +0800
From:	Ley Foon Tan <lftan@...era.com>
To:	<linux-arch@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-doc@...r.kernel.org>
CC:	Arnd Bergmann <arnd@...db.de>, Ley Foon Tan <lftan@...era.com>,
	<lftan.linux@...il.com>, <cltang@...esourcery.com>
Subject: [PATCH v6 01/29] asm-generic: add generic futex for !CONFIG_SMP

Follow m68k futex implementation for !CONFIG_SMP.

Signed-off-by: Ley Foon Tan <lftan@...era.com>
Acked-by: Arnd Bergmann <arnd@...db.de>
---
 include/asm-generic/futex.h | 114 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 114 insertions(+)

diff --git a/include/asm-generic/futex.h b/include/asm-generic/futex.h
index 01f227e..b59b5a5 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
-- 
1.8.2.1

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