linux-kernel - [PATCH] bitops: Move test_bit() into bitops/atomic.h

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Date:   Thu, 21 May 2020 15:31:29 +0100
From:   Will Deacon <will@...nel.org>
To:     linux-kernel@...r.kernel.org
Cc:     kernel-team@...roid.com, Will Deacon <will@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>
Subject: [PATCH] bitops: Move test_bit() into bitops/atomic.h

test_bit() is an atomic operation as documented by atomic_bitops.txt.
Move the function from bitops/non-atomic.h to bitops/atomic.h and adjust
its implementation to align with the other atomic bitops.

Cc: Peter Zijlstra <peterz@...radead.org>
Signed-off-by: Will Deacon <will@...nel.org>
---
 include/asm-generic/bitops/atomic.h     |  6 ++++++
 include/asm-generic/bitops/non-atomic.h | 10 ----------
 2 files changed, 6 insertions(+), 10 deletions(-)

Just found this kicking around on a branch from last year!

diff --git a/include/asm-generic/bitops/atomic.h b/include/asm-generic/bitops/atomic.h
index dd90c9792909..5fc4399d8fb4 100644
--- a/include/asm-generic/bitops/atomic.h
+++ b/include/asm-generic/bitops/atomic.h
@@ -17,6 +17,12 @@ static inline void set_bit(unsigned int nr, volatile unsigned long *p)
 	atomic_long_or(BIT_MASK(nr), (atomic_long_t *)p);
 }
 
+static inline int test_bit(unsigned int nr, const volatile unsigned long *p)
+{
+	p += BIT_WORD(nr);
+	return !!(READ_ONCE(*p) & BIT_MASK(nr));
+}
+
 static inline void clear_bit(unsigned int nr, volatile unsigned long *p)
 {
 	p += BIT_WORD(nr);
diff --git a/include/asm-generic/bitops/non-atomic.h b/include/asm-generic/bitops/non-atomic.h
index 7e10c4b50c5d..8b44da59a9d0 100644
--- a/include/asm-generic/bitops/non-atomic.h
+++ b/include/asm-generic/bitops/non-atomic.h
@@ -96,14 +96,4 @@ static inline int __test_and_change_bit(int nr,
 	return (old & mask) != 0;
 }
 
-/**
- * test_bit - Determine whether a bit is set
- * @nr: bit number to test
- * @addr: Address to start counting from
- */
-static inline int test_bit(int nr, const volatile unsigned long *addr)
-{
-	return 1UL & (addr[BIT_WORD(nr)] >> (nr & (BITS_PER_LONG-1)));
-}
-
 #endif /* _ASM_GENERIC_BITOPS_NON_ATOMIC_H_ */
-- 
2.26.2.761.g0e0b3e54be-goog