RE: [PATCH] bitops: fix issue in parallel atomic tests

["Morten Brørup" <mb@smartsharesystems.com>]

> From: Mattias Rönnblom [mailto:mattias.ronnblom@ericsson.com]
> Sent: Sunday, 13 October 2024 13.57
> 
> The macros generating the parallel test for atomic test-and-
> [set|clear|flip] functions used a 64-bit reference word when assuring
> no neighbouring bits were modified, even when generating code for the
> 32-bit version of the test.
> 
> This issue causes spurious test failures on GCC 12.2.0 (the default
> compiler on for example Debian 12 "bookworm"), when optimization level
> 2 or higher are used.
> 
> The test failures do not occur with GCC 11, 12.3 and 13.2.
> 
> To the author, this looks like a promotion-related compiler bug in GCC
> 12.2.

I am curious about the compiler bug...

Did the bug occur when the most significant bit was set, so it sign related?

Maybe this will reveal something:

TEST_ASSERT(expected_word == word,
  "Untouched bits have changed value, %" PRIx ## size
  " should be %" PRIx64,
  word, expected_word);

> 
> Fixes: 35326b61aecb ("bitops: add atomic bit operations in new API")
> 
> Signed-off-by: Mattias Rönnblom <mattias.ronnblom@ericsson.com>
> ---

I took a deep look into this.

Regardless of what the compiler bug is,

Reviewed-by: Morten Brørup <mb@smartsharesystems.com>