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

From: Haitao Huang
Date: Fri Jun 07 2024 - 10:23:43 EST


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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