lkml.org 
[lkml]   [2022]   [Jan]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [PATCH] ice: Don't use GFP_KERNEL in atomic context
From
Le 16/01/2022 à 22:42, Andrew Lunn a écrit :
> On Sun, Jan 16, 2022 at 07:46:20PM +0100, Christophe JAILLET wrote:
>> ice_misc_intr() is an irq handler. It should not sleep.
>>
>> Use GFP_ATOMIC instead of GFP_KERNEL when allocating some memory.
>>
>> Fixes: 348048e724a0 ("ice: Implement iidc operations")
>> Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
>> ---
>> I've never played a lot with irq handler. My understanding is that they
>> should never sleep.
>
> Hi Christophe
>
> Threaded interrupt handlers are allowed to sleep. However, this
> handler is not being used in such a way. So your are probably correct
> about GFP_KERNEL vs GFP_ATOMIC.
>
>> ---
>> drivers/net/ethernet/intel/ice/ice_main.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/net/ethernet/intel/ice/ice_main.c b/drivers/net/ethernet/intel/ice/ice_main.c
>> index 30814435f779..65de01f3a504 100644
>> --- a/drivers/net/ethernet/intel/ice/ice_main.c
>> +++ b/drivers/net/ethernet/intel/ice/ice_main.c
>> @@ -3018,7 +3018,7 @@ static irqreturn_t ice_misc_intr(int __always_unused irq, void *data)
>> struct iidc_event *event;
>>
>> ena_mask &= ~ICE_AUX_CRIT_ERR;
>> - event = kzalloc(sizeof(*event), GFP_KERNEL);
>> + event = kzalloc(sizeof(*event), GFP_ATOMIC);
>> if (event) {
>> set_bit(IIDC_EVENT_CRIT_ERR, event->type);
>> /* report the entire OICR value to AUX driver */
>
> What happens next is interesting...
>
>
> event->reg = oicr;
> ice_send_event_to_aux(pf, event);
>
> where:
>
> void ice_send_event_to_aux(struct ice_pf *pf, struct iidc_event *event)
> {
> struct iidc_auxiliary_drv *iadrv;
>
> if (!pf->adev)
> return;
>
> device_lock(&pf->adev->dev);
> iadrv = ice_get_auxiliary_drv(pf);
> if (iadrv && iadrv->event_handler)
> iadrv->event_handler(pf, event);
> device_unlock(&pf->adev->dev);
> }
>
> device_lock() takes a mutex, not something you should be doing in
> atomic context.
>
> So it looks to me, this handler really should be running in thread
> context...
>
> Andrew
>

Ok, thanks for the explanation.

ice_misc_intr() is registered with devm_request_irq(), so it is a
handler that can't sleep.

I guess that more consideration should be taken into account than only:
s/devm_request_irq(handler)/devm_request_threaded_irq(NULL, handler)/

So I'll leave this one to people with the expected know-how.

If my s/GFP_KERNEL/GFP_ATOMIC/ makes enough sense as-is, that's fine for
me, but it looks that another solution is needed to fix the 2nd issue.


CJ

\
 
 \ /
  Last update: 2022-01-18 21:02    [W:0.104 / U:0.168 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site