Re: [RFC PATCH v1 0/3] Fix undefined behavior in the C++ mutex implementation

[Ammar Faizi <ammarfaizi2@gnuweeb.org>]

On Sat, 11 Mar 2023 11:28:07 +0000, Alviro Iskandar Setiawan wrote:
> The current C++ mutex implementation is undefined behavior, specifically
> in the cond_wait() function because std::unique_lock<std::mutex> is
> constructed with std::defer_lock while the same thread has acquired the
> lock. Also, right after that defer_lock, std::condition_variable calls
> wait() with a unique lock, not in a locked state.
> 
> In such a situation, the correct construction is using std::adopt_lock.
> However, using std::adopt_lock leads to another issue. The issue is the
> lock will be released upon return in the cond_wait(). To solve the
> problem, introduce a new helper function, __cond_wait() which will
> release the lock with std::adopt_lock and then call it from cond_wait().
> The cond_wait() then acquires the lock again before it returns. The
> result is that we correctly fulfill the __must_hold() semantic while
> conforming to the C++ mutex implementation.
> 
> [...]

Applied, thanks!

[1/3] MAINTAINERS: Add myself as the thread maintainer
      commit: 5be6c427164522be650985c93595615c4f5c00e2
[2/3] core/thread: Fix undefined behavior in the C++ mutex implementation
      commit: bd84193e908c455c7c0c7f94a914d46b75557815
[3/3] configure: Introduce `--cpp-thread` option
      commit: 45b140357906d810f023ed1735a2b6585f4a5dce

Best regards,
-- 
Ammar Faizi