Re: [PATCH] ata: disable port while unloading ATA controller driver

[Tejun Heo <tj@kernel.org>]

Hello, Vladimir.

On Tue, Nov 29, 2016 at 08:54:11PM +0200, Vladimir Zapolskiy wrote:
> tracing on the board shows a race between driver initialization and
> deinitialization, when async_port_probe() is scheduled after driver
> removal, this causes the reported problem.
> 
> Since it is a race, it should be possible to fuzz the kernel by
> introducing a delay (e.g. in ata_port_probe()) to get enough time
> to reproduce the problem reliably and to verify a fix.
> 
> imx_ahci_probe()
>   ahci_platform_init_host()
>     ata_host_alloc_pinfo()
>       ata_host_alloc()
>         ata_port_alloc()    ---> sets ATA_PFLAG_INITIALIZING flag
>           ata_link_init()
>           ....
>     ahci_host_activate()
>       ata_host_activate()
>         ata_host_start()
>           ata_eh_freeze_port()
>         ata_port_desc()
>         ata_host_register() ---> schedules async_port_probe()
>   ....
> 
> *** at this point the driver probe is completed, thus it can be removed ***

Not really.  Is this from the unloading test config?  Control doesn't
get passed to userland until async probings are flushed, so this
shouldn't normally be possible.

Thanks.

-- 
tejun