Re: [PATCH v14 02/14] cgroup/misc: Add per resource callbacks for CSS events

[Haitao Huang]

On Thu, 06 Jun 2024 20:53:11 -0500, chenridong <chenridong@xxxxxxxxxx>  
wrote:

> I think it is better when _misc_cg_res_alloc fails, it just calls  
> _misc_cg_res_free(cg, index)(add index parameter, it means ending of  
> iterator), so it can avoid calling ->free() that do not call ->alloc().
>
> And in misc_cg_free, just call _misc_cg_res_free(cg, MISC_CG_RES_TYPES)   
> to free all.
That makes sense now, Will do that.
(BTW you need comment inline :-)
Thanks
Haitao

> On 2024/6/6 22:51, Haitao Huang wrote:
> > On Thu, 06 Jun 2024 08:37:31 -0500, chenridong <chenridong@xxxxxxxxxx>  
> > wrote:
> >
> > >   If _misc_cg_res_alloc fails, maybe some types do not call ->alloc(),  
> > > but all types ->free() callback >will be called, is that ok?
> > Not sure I understand. Are you suggesting we ignore failures from  
> > ->alloc() callback in _misc_cg_res_alloc() as it is per-resource, and  
> > have ->free() callback and resource provider of the failing type to  
> > handle the failure internally?
> >
> > IIUC, this failure only happens when a specific subcgroup is created  
> > (memory running out for allocation) so failing that subcgroup as a  
> > whole seems fine to me. Note the root node is static and no  
> > pre-resource callbacks invoked by misc. And resource provider handles  
> > its own allocations for root. In SGX case we too declare a static  
> > object for corresponding root sgx_cgroup struct.
> >
> > Note also misc cgroup (except for setting capacity[res] = 0 at root) is  
> > all or nothing so no mechanism to tell user "this resource does not  
> > work but others are fine in this particular cgroup."
> >
> > Thanks
> > Haitao


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