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Subject[PATCH v5 2/9] bitops: always define asm-generic non-atomic bitops
Date
Move generic non-atomic bitops from the asm-generic header which
gets included only when there are no architecture-specific
alternatives, to a separate independent file to make them always
available.
Almost no actual code changes, only one comment added to
generic_test_bit() saying that it's an atomic operation itself
and thus `volatile` must always stay there with no cast-aways.

Suggested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> # comment
Suggested-by: Marco Elver <elver@google.com> # reference to kernel-doc
Signed-off-by: Alexander Lobakin <alexandr.lobakin@intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Marco Elver <elver@google.com>
---
.../asm-generic/bitops/generic-non-atomic.h | 130 ++++++++++++++++++
include/asm-generic/bitops/non-atomic.h | 110 ++-------------
2 files changed, 138 insertions(+), 102 deletions(-)
create mode 100644 include/asm-generic/bitops/generic-non-atomic.h

diff --git a/include/asm-generic/bitops/generic-non-atomic.h b/include/asm-generic/bitops/generic-non-atomic.h
new file mode 100644
index 000000000000..7226488810e5
--- /dev/null
+++ b/include/asm-generic/bitops/generic-non-atomic.h
@@ -0,0 +1,130 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#ifndef __ASM_GENERIC_BITOPS_GENERIC_NON_ATOMIC_H
+#define __ASM_GENERIC_BITOPS_GENERIC_NON_ATOMIC_H
+
+#include <linux/bits.h>
+
+#ifndef _LINUX_BITOPS_H
+#error only <linux/bitops.h> can be included directly
+#endif
+
+/*
+ * Generic definitions for bit operations, should not be used in regular code
+ * directly.
+ */
+
+/**
+ * generic___set_bit - Set a bit in memory
+ * @nr: the bit to set
+ * @addr: the address to start counting from
+ *
+ * Unlike set_bit(), this function is non-atomic and may be reordered.
+ * If it's called on the same region of memory simultaneously, the effect
+ * may be that only one operation succeeds.
+ */
+static __always_inline void
+generic___set_bit(unsigned int nr, volatile unsigned long *addr)
+{
+ unsigned long mask = BIT_MASK(nr);
+ unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);
+
+ *p |= mask;
+}
+
+static __always_inline void
+generic___clear_bit(unsigned int nr, volatile unsigned long *addr)
+{
+ unsigned long mask = BIT_MASK(nr);
+ unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);
+
+ *p &= ~mask;
+}
+
+/**
+ * generic___change_bit - Toggle a bit in memory
+ * @nr: the bit to change
+ * @addr: the address to start counting from
+ *
+ * Unlike change_bit(), this function is non-atomic and may be reordered.
+ * If it's called on the same region of memory simultaneously, the effect
+ * may be that only one operation succeeds.
+ */
+static __always_inline
+void generic___change_bit(unsigned int nr, volatile unsigned long *addr)
+{
+ unsigned long mask = BIT_MASK(nr);
+ unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);
+
+ *p ^= mask;
+}
+
+/**
+ * generic___test_and_set_bit - Set a bit and return its old value
+ * @nr: Bit to set
+ * @addr: Address to count from
+ *
+ * This operation is non-atomic and can be reordered.
+ * If two examples of this operation race, one can appear to succeed
+ * but actually fail. You must protect multiple accesses with a lock.
+ */
+static __always_inline int
+generic___test_and_set_bit(unsigned int nr, volatile unsigned long *addr)
+{
+ unsigned long mask = BIT_MASK(nr);
+ unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);
+ unsigned long old = *p;
+
+ *p = old | mask;
+ return (old & mask) != 0;
+}
+
+/**
+ * generic___test_and_clear_bit - Clear a bit and return its old value
+ * @nr: Bit to clear
+ * @addr: Address to count from
+ *
+ * This operation is non-atomic and can be reordered.
+ * If two examples of this operation race, one can appear to succeed
+ * but actually fail. You must protect multiple accesses with a lock.
+ */
+static __always_inline int
+generic___test_and_clear_bit(unsigned int nr, volatile unsigned long *addr)
+{
+ unsigned long mask = BIT_MASK(nr);
+ unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);
+ unsigned long old = *p;
+
+ *p = old & ~mask;
+ return (old & mask) != 0;
+}
+
+/* WARNING: non atomic and it can be reordered! */
+static __always_inline int
+generic___test_and_change_bit(unsigned int nr, volatile unsigned long *addr)
+{
+ unsigned long mask = BIT_MASK(nr);
+ unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);
+ unsigned long old = *p;
+
+ *p = old ^ mask;
+ return (old & mask) != 0;
+}
+
+/**
+ * generic_test_bit - Determine whether a bit is set
+ * @nr: bit number to test
+ * @addr: Address to start counting from
+ */
+static __always_inline int
+generic_test_bit(unsigned int nr, const volatile unsigned long *addr)
+{
+ /*
+ * Unlike the bitops with the '__' prefix above, this one *is* atomic,
+ * so `volatile` must always stay here with no cast-aways. See
+ * `Documentation/atomic_bitops.txt` for the details.
+ */
+ return 1UL & (addr[BIT_WORD(nr)] >> (nr & (BITS_PER_LONG-1)));
+}
+
+#endif /* __ASM_GENERIC_BITOPS_GENERIC_NON_ATOMIC_H */
diff --git a/include/asm-generic/bitops/non-atomic.h b/include/asm-generic/bitops/non-atomic.h
index 078cc68be2f1..23d3abc1e10d 100644
--- a/include/asm-generic/bitops/non-atomic.h
+++ b/include/asm-generic/bitops/non-atomic.h
@@ -2,121 +2,27 @@
#ifndef _ASM_GENERIC_BITOPS_NON_ATOMIC_H_
#define _ASM_GENERIC_BITOPS_NON_ATOMIC_H_

-#include <asm/types.h>
+#include <asm-generic/bitops/generic-non-atomic.h>

-/**
- * arch___set_bit - Set a bit in memory
- * @nr: the bit to set
- * @addr: the address to start counting from
- *
- * Unlike set_bit(), this function is non-atomic and may be reordered.
- * If it's called on the same region of memory simultaneously, the effect
- * may be that only one operation succeeds.
- */
-static __always_inline void
-arch___set_bit(unsigned int nr, volatile unsigned long *addr)
-{
- unsigned long mask = BIT_MASK(nr);
- unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);
-
- *p |= mask;
-}
+#define arch___set_bit generic___set_bit
#define __set_bit arch___set_bit

-static __always_inline void
-arch___clear_bit(unsigned int nr, volatile unsigned long *addr)
-{
- unsigned long mask = BIT_MASK(nr);
- unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);
-
- *p &= ~mask;
-}
+#define arch___clear_bit generic___clear_bit
#define __clear_bit arch___clear_bit

-/**
- * arch___change_bit - Toggle a bit in memory
- * @nr: the bit to change
- * @addr: the address to start counting from
- *
- * Unlike change_bit(), this function is non-atomic and may be reordered.
- * If it's called on the same region of memory simultaneously, the effect
- * may be that only one operation succeeds.
- */
-static __always_inline
-void arch___change_bit(unsigned int nr, volatile unsigned long *addr)
-{
- unsigned long mask = BIT_MASK(nr);
- unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);
-
- *p ^= mask;
-}
+#define arch___change_bit generic___change_bit
#define __change_bit arch___change_bit

-/**
- * arch___test_and_set_bit - Set a bit and return its old value
- * @nr: Bit to set
- * @addr: Address to count from
- *
- * This operation is non-atomic and can be reordered.
- * If two examples of this operation race, one can appear to succeed
- * but actually fail. You must protect multiple accesses with a lock.
- */
-static __always_inline int
-arch___test_and_set_bit(unsigned int nr, volatile unsigned long *addr)
-{
- unsigned long mask = BIT_MASK(nr);
- unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);
- unsigned long old = *p;
-
- *p = old | mask;
- return (old & mask) != 0;
-}
+#define arch___test_and_set_bit generic___test_and_set_bit
#define __test_and_set_bit arch___test_and_set_bit

-/**
- * arch___test_and_clear_bit - Clear a bit and return its old value
- * @nr: Bit to clear
- * @addr: Address to count from
- *
- * This operation is non-atomic and can be reordered.
- * If two examples of this operation race, one can appear to succeed
- * but actually fail. You must protect multiple accesses with a lock.
- */
-static __always_inline int
-arch___test_and_clear_bit(unsigned int nr, volatile unsigned long *addr)
-{
- unsigned long mask = BIT_MASK(nr);
- unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);
- unsigned long old = *p;
-
- *p = old & ~mask;
- return (old & mask) != 0;
-}
+#define arch___test_and_clear_bit generic___test_and_clear_bit
#define __test_and_clear_bit arch___test_and_clear_bit

-/* WARNING: non atomic and it can be reordered! */
-static __always_inline int
-arch___test_and_change_bit(unsigned int nr, volatile unsigned long *addr)
-{
- unsigned long mask = BIT_MASK(nr);
- unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);
- unsigned long old = *p;
-
- *p = old ^ mask;
- return (old & mask) != 0;
-}
+#define arch___test_and_change_bit generic___test_and_change_bit
#define __test_and_change_bit arch___test_and_change_bit

-/**
- * arch_test_bit - Determine whether a bit is set
- * @nr: bit number to test
- * @addr: Address to start counting from
- */
-static __always_inline int
-arch_test_bit(unsigned int nr, const volatile unsigned long *addr)
-{
- return 1UL & (addr[BIT_WORD(nr)] >> (nr & (BITS_PER_LONG-1)));
-}
+#define arch_test_bit generic_test_bit
#define test_bit arch_test_bit

#endif /* _ASM_GENERIC_BITOPS_NON_ATOMIC_H_ */
--
2.36.1
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