[PATCH] bitops: Add a comment explaining the double underscore macros

[Dan Carpenter]

Linus Walleij pointed out that a new comer might be confused about the
difference between set_bit() and __set_bit().  Add a comment explaining
the difference.

Link: https://lore.kernel.org/all/CACRpkdZFPG_YLici-BmYfk9HZ36f4WavCN3JNotkk8cPgCODCg@xxxxxxxxxxxxxx/
Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
---
v2: re-word the comment, put it right next to the macros and add a blank
    line in front of the test_bit() macros so it's not mixed in with the
    non-atomic macros

 include/linux/bitops.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/include/linux/bitops.h b/include/linux/bitops.h
index 46d4bdc634c0..ba35bbf07798 100644
--- a/include/linux/bitops.h
+++ b/include/linux/bitops.h
@@ -47,12 +47,17 @@ extern unsigned long __sw_hweight64(__u64 w);
 	  __builtin_constant_p(*(const unsigned long *)(addr))) ?	\
 	 const##op(nr, addr) : op(nr, addr))
 
+/*
+ * The following macros are non-atomic versions of their non-underscored
+ * counterparts.
+ */
 #define __set_bit(nr, addr)		bitop(___set_bit, nr, addr)
 #define __clear_bit(nr, addr)		bitop(___clear_bit, nr, addr)
 #define __change_bit(nr, addr)		bitop(___change_bit, nr, addr)
 #define __test_and_set_bit(nr, addr)	bitop(___test_and_set_bit, nr, addr)
 #define __test_and_clear_bit(nr, addr)	bitop(___test_and_clear_bit, nr, addr)
 #define __test_and_change_bit(nr, addr)	bitop(___test_and_change_bit, nr, addr)
+
 #define test_bit(nr, addr)		bitop(_test_bit, nr, addr)
 #define test_bit_acquire(nr, addr)	bitop(_test_bit_acquire, nr, addr)
 
-- 
2.39.2