Re: [PATCH v3 2/4] membarrier: Add an actual barrier before rseq_preempt()

[Andy Lutomirski]

On Thu, Dec 3, 2020 at 9:07 PM Andy Lutomirski <luto@xxxxxxxxxx> wrote:
>
> It seems to me that most RSEQ membarrier users will expect any
> stores done before the membarrier() syscall to be visible to the
> target task(s).  While this is extremely likely to be true in
> practice, nothing actually guarantees it by a strict reading of the
> x86 manuals.  Rather than providing this guarantee by accident and
> potentially causing a problem down the road, just add an explicit
> barrier.
>
> Cc: stable@xxxxxxxxxxxxxxx

Fixes: 2a36ab717e8f ("rseq/membarrier: Add
MEMBARRIER_CMD_PRIVATE_EXPEDITED_RSEQ")

which is new in 5.10, so it doesn't need cc:stable if it makes 5.10.