Re: [PATCH] scsi: ata: Fix a race condition between scsi error handler and ahci interrupt

[Li Nan]

Thanks for your reply, Niklas.

在 2023/8/21 21:51, Niklas Cassel 写道:
> On Thu, Aug 10, 2023 at 09:48:48AM +0800, linan666@xxxxxxxxxxxxxxx wrote:

[snip]

> Hello Li Nan,
>
> I do not understand why the code in:
> https://github.com/torvalds/linux/blob/v6.5-rc7/drivers/ata/libata-eh.c#L722-L731
>
> does not kick in, and repeats EH.
>
>
> EH_PENDING is cleared before ->error_handler() is called:
> https://github.com/torvalds/linux/blob/v6.5-rc7/drivers/ata/libata-eh.c#L697
>
> So ahci_error_intr() from the second error interrupt, which is called after
> thawing the port, should have called ata_std_sched_eh(), which calls
> ata_eh_set_pending(), which should have set EH_PENDING:
> https://github.com/torvalds/linux/blob/v6.5-rc7/drivers/ata/libata-eh.c#L884
>
>
>
> My only guess is that after thawing the port:
> https://github.com/torvalds/linux/blob/v6.5-rc7/drivers/ata/libata-eh.c#L2807
>
> The second error irq comes, and sets EH_PENDING,
> but then this silly code might clear it:
> https://github.com/torvalds/linux/blob/v6.5-rc7/drivers/ata/libata-eh.c#L2825-L2837

Yeah, I think so.

> I think the best way would be if we could improve this "spurious error
> condition check"... because if this is indeed the code that clears EH_PENDING
> for you, then this code basically makes the "goto repeat" code in
> ata_scsi_port_error_handler() useless...
>
>
> An alternative to improving the "spurious error condition check" might be for
> you to try something like:

We have used this solution before, but it will case WARN_ON in
ata_eh_finish() as below:

  WARNING: CPU: 1 PID: 118 at ../drivers/ata/libata-eh.c:4016 
ata_eh_finish+0x15a/0x170

  ata_do_eh+0x70/0xf0
  ata_sff_error_handler+0xde/0x170
  ata_bmdma_error_handler+0x5b/0x1e0
  ata_scsi_port_error_handler+0x5b1/0xae0
  ata_scsi_error+0xb9/0x110
  scsi_error_handler+0x137/0x8d0

> diff --git a/drivers/ata/libata-eh.c b/drivers/ata/libata-eh.c
> index 35e03679b0bf..82f032934ae1 100644
> --- a/drivers/ata/libata-eh.c
> +++ b/drivers/ata/libata-eh.c
> @@ -962,7 +962,7 @@ void ata_std_end_eh(struct ata_port *ap)
>   {
>          struct Scsi_Host *host = ap->scsi_host;
>   
> -       host->host_eh_scheduled = 0;
> +       host->host_eh_scheduled--;
>   }
>   EXPORT_SYMBOL(ata_std_end_eh);
>
>
>
> ...and see if that improves things for you.
>
>
>
> Kind regards,
> Niklas.

--
Thanks,
Nan