[PATCH 1/2] asm-generic/bitops: Add set_bit_release()

[Philipp Stanner]

The kernel already has test_bit_acquire(). A set_bit_release(), however,
was missing so far. It can be expected to be useful for parties that
need release ordering, but not the stricter full ordering of the other
bit-setting functions.

Add set_bit_release().

Signed-off-by: Philipp Stanner <phasta@xxxxxxxxxx>
---
 include/asm-generic/bitops/instrumented-atomic.h | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/include/asm-generic/bitops/instrumented-atomic.h b/include/asm-generic/bitops/instrumented-atomic.h
index c010d54275e4..fb2d1472fd4d 100644
--- a/include/asm-generic/bitops/instrumented-atomic.h
+++ b/include/asm-generic/bitops/instrumented-atomic.h
@@ -72,6 +72,20 @@ static __always_inline bool test_and_set_bit(long nr, volatile unsigned long *ad
 	return arch_test_and_set_bit(nr, addr);
 }
 
+/**
+ * set_bit_release - Set a bit with release ordering
+ * @nr: Bit to set
+ * @addr: Address to start counting from
+ *
+ * This is an atomic ordered operation (implied write memory barrier).
+ */
+static __always_inline void set_bit_release(long nr, volatile unsigned long *addr)
+{
+	kcsan_wmb();
+	instrument_atomic_write(addr + BIT_WORD(nr), sizeof(long));
+	arch_set_bit(nr, addr);
+}
+
 /**
  * test_and_clear_bit - Clear a bit and return its old value
  * @nr: Bit to clear
-- 
2.56.0