From: Alexander Lobakin
Sent: 15 June 2022 14:55
...
+/**
+ * const_test_bit - Determine whether a bit is set
+ * @nr: bit number to test
+ * @addr: Address to start counting from
+ *
+ * A version of generic_test_bit() which discards the `volatile` qualifier to
+ * allow the compiler to optimize code harder. Non-atomic and to be used only
+ * for testing compile-time constants, e.g. from the corresponding macro, or
+ * when you really know what you are doing.
Not sure I understand the last sentence... Can you please rephrase?
I basically want to tell that there potentinally might be cases for
using those outside of the actual macros from 6/6. But it might be
redundant at all to mention this.
I bet that is a function has:
long bitmask;
...
if (test_bit(&bitmask, 12))
then the 'volatile' forces the compiler to actually write the
value out to memory (stack) instead of doing a register op.
OTOH such code should be using &.
David
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