On Tue, Dec 17, 2024 at 02:22:29PM -0800, Daniel Xu wrote:
> WRITE_ONCE() is needed here to prevent store tears and other unwanted
> compiler optimizations.
>
> Signed-off-by: Daniel Xu <dxu@xxxxxxxxx>
I am pulling this in despite the misgivings on this thread. If the kernel
gets an INC_ONCE(), maybe perfbook should too. But in the meantime...
Thanx, Paul
> ---
> CodeSamples/defer/seqlock.h | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/CodeSamples/defer/seqlock.h b/CodeSamples/defer/seqlock.h
> index ec00177b..842d10a6 100644
> --- a/CodeSamples/defer/seqlock.h
> +++ b/CodeSamples/defer/seqlock.h
> @@ -60,14 +60,14 @@ static inline int read_seqretry(seqlock_t *slp, //\lnlbl{read_seqretry:b}
> static inline void write_seqlock(seqlock_t *slp) //\lnlbl{write_seqlock:b}
> {
> spin_lock(&slp->lock);
> - ++slp->seq;
> + WRITE_ONCE(slp->seq, READ_ONCE(slp->seq) + 1);
> smp_mb();
> } //\lnlbl{write_seqlock:e}
>
> static inline void write_sequnlock(seqlock_t *slp) //\lnlbl{write_sequnlock:b}
> {
> smp_mb(); //\lnlbl{write_sequnlock:mb}
> - ++slp->seq; //\lnlbl{write_sequnlock:inc}
> + WRITE_ONCE(slp->seq, READ_ONCE(slp->seq) + 1); //\lnlbl{write_sequnlock:inc}
> spin_unlock(&slp->lock);
> } //\lnlbl{write_sequnlock:e}
> //\end{snippet}
> --
> 2.47.0
>
