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[1/5] tools: introduce test_and_clear_bit

Message ID 20180820075400.18847-2-peterx@redhat.com (mailing list archive)
State New, archived
Headers show
Series kvm: selftest: add dirty logging test | expand

Commit Message

Peter Xu Aug. 20, 2018, 7:53 a.m. UTC 
We have test_and_set_bit but not test_and_clear_bit.  Add it.

Signed-off-by: Peter Xu <peterx@redhat.com>
---
 tools/include/linux/bitmap.h | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)
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Patch

diff --git a/tools/include/linux/bitmap.h b/tools/include/linux/bitmap.h
index 63440cc8d618..e63662db131b 100644
--- a/tools/include/linux/bitmap.h
+++ b/tools/include/linux/bitmap.h
@@ -96,6 +96,23 @@  static inline int test_and_set_bit(int nr, unsigned long *addr)
 	return (old & mask) != 0;
 }
 
+/**
+ * test_and_clear_bit - Clear a bit and return its old value
+ * @nr: Bit to clear
+ * @addr: Address to count from
+ */
+static inline int test_and_clear_bit(int nr, unsigned long *addr)
+{
+	unsigned long mask = BIT_MASK(nr);
+	unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);
+	unsigned long old;
+
+	old = *p;
+	*p = old & ~mask;
+
+	return (old & mask) != 0;
+}
+
 /**
  * bitmap_alloc - Allocate bitmap
  * @nbits: Number of bits