Re: [PATCH 08/12] powerpc: Annotate accesses to ipi message flags

[Nicholas Piggin]

On Mon May 8, 2023 at 12:01 PM AEST, Rohan McLure wrote:
> IPI message flags are observed and consequently consumed in the
> smp_ipi_demux_relaxed function, which handles these message sources
> until it observes none more arriving. Mark the checked loop guard with
> READ_ONCE, to signal to KCSAN that the read is known to be volatile, and
> that non-determinism is expected.

smp_muxed_ipi_set_message() doesn't need a WRITE_ONCE()?

Thanks,
Nick

>
> Signed-off-by: Rohan McLure 
> ---
>  arch/powerpc/kernel/smp.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
> index 6b90f10a6c81..00b74d66b771 100644
> --- a/arch/powerpc/kernel/smp.c
> +++ b/arch/powerpc/kernel/smp.c
> @@ -348,7 +348,7 @@ irqreturn_t smp_ipi_demux_relaxed(void)
>   if (all & IPI_MESSAGE(PPC_MSG_NMI_IPI))
>   nmi_ipi_action(0, NULL);
>  #endif
> - } while (info->messages);
> + } while (READ_ONCE(info->messages));
>  
>   return IRQ_HANDLED;
>  }
> -- 
> 2.37.2

[PATCH 08/12] powerpc: Annotate accesses to ipi message flags

[Rohan McLure]

IPI message flags are observed and consequently consumed in the
smp_ipi_demux_relaxed function, which handles these message sources
until it observes none more arriving. Mark the checked loop guard with
READ_ONCE, to signal to KCSAN that the read is known to be volatile, and
that non-determinism is expected.

Signed-off-by: Rohan McLure 
---
 arch/powerpc/kernel/smp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
index 6b90f10a6c81..00b74d66b771 100644
--- a/arch/powerpc/kernel/smp.c
+++ b/arch/powerpc/kernel/smp.c
@@ -348,7 +348,7 @@ irqreturn_t smp_ipi_demux_relaxed(void)
if (all & IPI_MESSAGE(PPC_MSG_NMI_IPI))
nmi_ipi_action(0, NULL);
 #endif
-   } while (info->messages);
+   } while (READ_ONCE(info->messages));
 
return IRQ_HANDLED;
 }
-- 
2.37.2