On Mon May 8, 2023 at 12:01 PM AEST, Rohan McLure wrote:
> The kopald thread handles opal events as they appear, but by polling a
> static bit-vector in last_outstanding_events. Annotate these data races
> accordingly. We are not at risk of missing events, but use of READ_ONCE,
> WRITE_ONCE will assist readers in seeing that kopald only consumes the
> events it is aware of when it is scheduled. Also removes extraneous
> KCSAN warnings.
This code is fairly crap, which I can say because I wrote it :(
But this at least is an improvement. Thanks.
Reviewed-by: Nicholas Piggin <npig...@gmail.com>
>
> Signed-off-by: Rohan McLure <rmcl...@linux.ibm.com>
> ---
> arch/powerpc/platforms/powernv/opal-irqchip.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/arch/powerpc/platforms/powernv/opal-irqchip.c
> b/arch/powerpc/platforms/powernv/opal-irqchip.c
> index d55652b5f6fa..f9a7001dacb7 100644
> --- a/arch/powerpc/platforms/powernv/opal-irqchip.c
> +++ b/arch/powerpc/platforms/powernv/opal-irqchip.c
> @@ -59,7 +59,7 @@ void opal_handle_events(void)
>
> cond_resched();
> }
> - last_outstanding_events = 0;
> + WRITE_ONCE(last_outstanding_events, 0);
> if (opal_poll_events(&events) != OPAL_SUCCESS)
> return;
> e = be64_to_cpu(events) & opal_event_irqchip.mask;
> @@ -69,7 +69,7 @@ void opal_handle_events(void)
>
> bool opal_have_pending_events(void)
> {
> - if (last_outstanding_events & opal_event_irqchip.mask)
> + if (READ_ONCE(last_outstanding_events) & opal_event_irqchip.mask)
> return true;
> return false;
> }
> @@ -124,7 +124,7 @@ static irqreturn_t opal_interrupt(int irq, void *data)
> __be64 events;
>
> opal_handle_interrupt(virq_to_hw(irq), &events);
> - last_outstanding_events = be64_to_cpu(events);
> + WRITE_ONCE(last_outstanding_events, be64_to_cpu(events));
> if (opal_have_pending_events())
> opal_wake_poller();
>
> --
> 2.37.2
