[PATCH 2/3] lib: sbi_ipi: Process self-IPIs in sbi_ipi_send()

[Anup Patel]

On Sat, Dec 9, 2023 at 2:53 AM Samuel Holland <samuel.holland at sifive.com> wrote:
>
> An IPI sent to the local hart can be processed directly instead of
> triggering the IPI device. This is more efficient, and it avoids a
> deadlock when the .sync callback is defined. Since interrupts are
> disabled while handling an ecall, the IPI would not get delivered
> until the next mret, but sbi_ipi_sync() is called before then.
>
> Signed-off-by: Samuel Holland <samuel.holland at sifive.com>

Looks good to me.

Reviewed-by: Anup Patel <anup at brainfault.org>

Regards,
Anup

> ---
>
>  lib/sbi/sbi_ipi.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
>
> diff --git a/lib/sbi/sbi_ipi.c b/lib/sbi/sbi_ipi.c
> index 1fd24228..ac31cd94 100644
> --- a/lib/sbi/sbi_ipi.c
> +++ b/lib/sbi/sbi_ipi.c
> @@ -60,6 +60,14 @@ static int sbi_ipi_send(struct sbi_scratch *scratch, u32 remote_hartindex,
>                                       remote_hartindex, data);
>                 if (ret != SBI_IPI_UPDATE_SUCCESS)
>                         return ret;
> +       } else if (scratch == remote_scratch) {
> +               /*
> +                * IPI events with an update() callback are expected to return
> +                * SBI_IPI_UPDATE_BREAK for self-IPIs. For other events, check
> +                * for self-IPI and execute the callback directly here.
> +                */
> +               ipi_ops->process(scratch);
> +               return 0;
>         }
>
>         /*
> --
> 2.42.0
>
>
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