On Mon, Jun 13, 2022 at 04:33:17PM +0200, Marco Elver wrote:
On Mon, 13 Jun 2022 at 16:21, Alexander Lobakin
<alexandr.lobakin@xxxxxxxxx> wrote:
From: Marco Elver <elver@xxxxxxxxxx>
Date: Fri, 10 Jun 2022 18:32:36 +0200
On Fri, 10 Jun 2022 at 18:02, Luck, Tony <tony.luck@xxxxxxxxx> wrote:
+/**
+ * generic_test_bit - Determine whether a bit is set
+ * @nr: bit number to test
+ * @addr: Address to start counting from
+ */
Shouldn't we add in this or in separate patch a big NOTE to explain that this
is actually atomic and must be kept as a such?
"atomic" isn't really the right word. The volatile access makes sure that the
compiler does the test at the point that the source code asked, and doesn't
move it before/after other operations.
It's listed in Documentation/atomic_bitops.txt.
Oh, so my memory was actually correct that I saw it in the docs
somewhere.
WDYT, should I mention this here in the code (block comment) as well
that it's atomic and must not lose `volatile` as Andy suggested or
it's sufficient to have it in the docs (+ it's not underscored)?
Perhaps a quick comment in the code (not kerneldoc above) will be
sufficient, with reference to Documentation/atomic_bitops.txt.
If it may help, we can do:
/*
* Bit testing is a naturally atomic operation because bit is
* a minimal quantum of information.
*/
#define __test_bit test_bit
