Re: [PATCH v2 0/9] thread_info: use helpers to snapshot thread flags

[Will Deacon]

On Mon, Jun 21, 2021 at 10:05:52AM +0100, Mark Rutland wrote:
> As thread_info::flags scan be manipulated by remote threads, it is
> necessary to use atomics or READ_ONCE() to ensure that code manipulates
> a consistent snapshot, but we open-code plain accesses to
> thread_info::flags across the kernel tree.
> 
> Generally we get away with this, but tools like KCSAN legitimately warn
> that there is a data-race, and this is potentially fragile with compiler
> optimizations, LTO, etc.
> 
> These patches introduce new helpers to snahpshot the thread flags, with
> the intent being that these should replace all plain accesses.
> 
> Since v1 [1]:
> * Drop RFC
> * Make read_ti_thread_flags() __always_inline
> * Clarify commit messages
> * Fix typo in arm64 patch
> * Accumulate Reviewed-by / Acked-by tags
> * Drop powerpc patch to avoid potential conflicts (per [2])
> 
> [1] https://lore.kernel.org/r/20210609122001.18277-1-mark.rutland@xxxxxxx
> [2] https://lore.kernel.org/r/87k0mvtgeb.fsf@xxxxxxxxxxxxxxxxxx
> 
> Thanks,
> Mark.
> 
> Mark Rutland (9):
>   thread_info: add helpers to snapshot thread flags
>   entry: snapshot thread flags
>   sched: snapshot thread flags
>   alpha: snapshot thread flags
>   arm: snapshot thread flags
>   arm64: snapshot thread flags

FWIW, you have two identical arm64 patches in this series, just with a
different subject. For the one you decide to keep:

Acked-by: Will Deacon <will@xxxxxxxxxx>

Will