Re: [PATCH v1] ALSA: memalloc: Fix indefinite hang in non-iommu case

[Takashi Iwai <tiwai@xxxxxxx>]

On Fri, 16 Feb 2024 05:34:24 +0100,
Hillf Danton wrote:
> 
> On Thu, 15 Feb 2024 18:03:01 +0100 Takashi Iwai <tiwai@xxxxxxx> wrote:
> > 
> > So it sounds like that we should go back for __GFP_NORETRY in general
> > for non-zero order allocations, not only the call you changed, as
> > __GFP_RETRY_MAYFAIL doesn't guarantee the stuck.
> > 
> > How about the changes like below?
> > 
> > +/* default GFP bits for our allocations */
> > +static gfp_t default_gfp(size_t size)
> > +{
> > +	/* don't allocate intensively for high-order pages */
> > +	if (size > PAGE_SIZE)
> > +		return GFP_KERNEL | __GFP_NOWARN | __GFP_NORETRY;
> > +	else
> > +		return GFP_KERNEL | __GFP_NOWARN | __GFP_RETRY_MAYFAIL;
> > +}
> 
> Looks like an overdose because both __GFP_NORETRY and __GFP_RETRY_MAYFAIL
> are checked in __alloc_pages_slowpath().

If the check there worked as expected, this shouldn't have been a
problem, no?

The fact that we have to drop __GFP_RETRY_MAYFAIL indicates that the
handling there doesn't suffice -- at least for the audio operation.


thanks,

Takashi