[PATCH 2/8] powerpc/eeh: Clear stale EEH_DEV_NO_HANDLER flag

Alexey Kardashevskiy aik at ozlabs.ru
Wed Mar 20 17:02:57 AEDT 2019

On 20/03/2019 13:58, Sam Bobroff wrote:
> The EEH_DEV_NO_HANDLER flag is used by the EEH system to prevent the
> use of driver callbacks in drivers that have been bound part way
> through the recovery process. This is necessary to prevent later stage
> handlers from being called when the earlier stage handlers haven't,
> which can be confusing for drivers.

The flag is used from eeh_pe_report()->eeh_pe_report_edev which is
called many times from eeh_handle_normal_event() (and you clear the flag
here unconditionally) and once from eeh_handle_special_event() - so this
is actually the only case now when the flag matters. Is my understanding
correct? Also is not clearing the flag correct in that case? I do not
quite understand eeh_handle_normal_event vs. eeh_handle_special_event
business though.

> However, the flag is set for all devices that are added after boot
> time and only cleared at the end of the EEH recovery process. This
> results in hot plugged devices erroneously having the flag set during
> the first recovery after they are added (causing their driver's
> handlers to be incorrectly ignored).
> To remedy this, clear the flag at the beginning of recovery
> processing. The flag is still cleared at the end of recovery
> processing, although it is no longer really necessary.

Then may be remove that redundant clearing?

> Signed-off-by: Sam Bobroff <sbobroff at linux.ibm.com>
> ---
>  arch/powerpc/kernel/eeh_driver.c | 4 ++++
>  1 file changed, 4 insertions(+)
> diff --git a/arch/powerpc/kernel/eeh_driver.c b/arch/powerpc/kernel/eeh_driver.c
> index 6f3ee30565dd..4c34b9901f15 100644
> --- a/arch/powerpc/kernel/eeh_driver.c
> +++ b/arch/powerpc/kernel/eeh_driver.c
> @@ -819,6 +819,10 @@ void eeh_handle_normal_event(struct eeh_pe *pe)
>  	}
> +	eeh_for_each_pe(pe, tmp_pe)
> +		eeh_pe_for_each_dev(tmp_pe, edev, tmp)
> +			edev->mode &= ~EEH_DEV_NO_HANDLER;
> +
>  	/* Walk the various device drivers attached to this slot through
>  	 * a reset sequence, giving each an opportunity to do what it needs
>  	 * to accomplish the reset.  Each child gets a report of the


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