[PATCH 2/2] lib: sbi: Make ipi send/clear and access ipi_type non-reentrant

[Xiang W]

在 2023-11-20星期一的 17:52 +0800，Xiang W写道：
> Sending/receiving ipi messages and setting ipi_type should be
> non-reentrant. If reentrant, unexpected errors may occur.
If reentrant, the following case may occur:

                hart A             hart B
send ipi--------->|                  |
                  | clear ipi        | 
                  |                  | set ipi_type
                  |                  |
                  | xchg ipi_type    |
                  |                  |
                  |<-----------------| send ipi
                  |                  |
                  |                  |

For more discussion, please refer to
https://lists.infradead.org/pipermail/opensbi/2023-November/005817.html

Regards,
Xiang W
> 
> Signed-off-by: Xiang W <wxjstz at 126.com>
> Reported-by: Bo Gan <ganboing at gmail.com>
> ---
>  lib/sbi/sbi_ipi.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/lib/sbi/sbi_ipi.c b/lib/sbi/sbi_ipi.c
> index 30cb315..8e05d28 100644
> --- a/lib/sbi/sbi_ipi.c
> +++ b/lib/sbi/sbi_ipi.c
> @@ -11,6 +11,7 @@
>  #include <sbi/riscv_asm.h>
>  #include <sbi/riscv_atomic.h>
>  #include <sbi/riscv_barrier.h>
> +#include <sbi/riscv_locks.h>
>  #include <sbi/sbi_bitops.h>
>  #include <sbi/sbi_domain.h>
>  #include <sbi/sbi_error.h>
> @@ -25,6 +26,7 @@
>  
>  struct sbi_ipi_data {
>  	unsigned long ipi_type;
> +	spinlock_t lock;
>  };
>  
>  _Static_assert(
> @@ -66,9 +68,11 @@ 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
>  	 */
> +	spin_lock(&ipi_data->lock);
>  	atomic_raw_set_bit(event, &ipi_data->ipi_type);
>  	smp_wmb();
>  	sbi_ipi_raw_send(remote_hartindex);
> +	spin_unlock(&ipi_data->lock);
>  
>  	sbi_pmu_ctr_incr_fw(SBI_PMU_FW_IPI_SENT);
>  
> @@ -220,8 +224,12 @@ void sbi_ipi_process(void)
>  	u32 hartindex = sbi_hartid_to_hartindex(current_hartid());
>  
>  	sbi_pmu_ctr_incr_fw(SBI_PMU_FW_IPI_RECVD);
> +
> +	spin_lock(&ipi_data->lock);
>  	sbi_ipi_raw_clear(hartindex);
>  	ipi_type = atomic_raw_xchg_ulong(&ipi_data->ipi_type, 0);
> +	spin_unlock(&ipi_data->lock);
> +
>  	ipi_event = 0;
>  	while (ipi_type) {
>  		if (ipi_type & 1UL) {
> @@ -289,6 +297,7 @@ int sbi_ipi_init(struct sbi_scratch *scratch, bool cold_boot)
>  
>  	ipi_data = sbi_scratch_offset_ptr(scratch, ipi_data_off);
>  	ipi_data->ipi_type = 0x00;
> +	SPIN_LOCK_INIT(ipi_data->lock);
>  
>  	/*
>  	 * Initialize platform IPI support. This will also clear any