[PATCH] lib: sbi: Prevent redundant sbi_ipi_process

[Xiang W]

在 2023-11-22星期三的 20:54 +0800，Xiang W写道：
> sbi_ipi_process reads ipi_type through xchg. This may occur between
> set ipi_type and send_ipi, which will result in redundant interrupt
> processing.
> 
> The specific case is as follows:
> 
>                 hart A             hart B
> send ipi--------->|                  |
>                   | clear ipi        |
>                   |                  | set ipi_type
>                   |                  |
>                   | xchg ipi_type    |
>                   |                  |
>                   |<-----------------| send ipi
>                   |                  |
>                   |                  |
> 
> This patch fixes this issue.

This patch base on
https://github.com/avpatel/opensbi/tree/sbi_ipi_barrier_imp_v1

Regards,
Xiang W
> 
> Signed-off-by: Xiang W <wxjstz at 126.com>
> ---
>  lib/sbi/sbi_ipi.c | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
> 
> diff --git a/lib/sbi/sbi_ipi.c b/lib/sbi/sbi_ipi.c
> index 0bf446a..6f25a7e 100644
> --- a/lib/sbi/sbi_ipi.c
> +++ b/lib/sbi/sbi_ipi.c
> @@ -39,7 +39,7 @@ static const struct sbi_ipi_event_ops *ipi_ops_array[SBI_IPI_EVENT_MAX];
>  static int sbi_ipi_send(struct sbi_scratch *scratch, u32 remote_hartindex,
>  			u32 event, void *data)
>  {
> -	int ret;
> +	int ret = 0;
>  	struct sbi_scratch *remote_scratch = NULL;
>  	struct sbi_ipi_data *ipi_data;
>  	const struct sbi_ipi_event_ops *ipi_ops;
> @@ -66,9 +66,8 @@ static int sbi_ipi_send(struct sbi_scratch *scratch, u32 remote_hartindex,
>  	 * Set IPI type on remote hart's scratch area and
>  	 * trigger the interrupt
>  	 */
> -	atomic_raw_set_bit(event, &ipi_data->ipi_type);
> -
> -	ret = sbi_ipi_raw_send(remote_hartindex);
> +	if (__atomic_fetch_or(&ipi_data->ipi_type, BIT(event), __ATOMIC_ACQ_REL) == 0)
> +		ret = sbi_ipi_raw_send(remote_hartindex);
>  
>  	sbi_pmu_ctr_incr_fw(SBI_PMU_FW_IPI_SENT);
>