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Subject: Re: [PATCH v14 02/14] cgroup/misc: Add per resource callbacks for CSS
 events
References: <20240531222630.4634-1-haitao.huang@linux.intel.com>
 <20240531222630.4634-3-haitao.huang@linux.intel.com>
 <eeb1f936-2989-4de0-8353-b2373ce47474@huawei.com>
Date: Thu, 06 Jun 2024 09:51:55 -0500
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From: "Haitao Huang" <haitao.huang@linux.intel.com>
Organization: Intel
Message-ID: <op.2ox8wt11wjvjmi@hhuan26-mobl.amr.corp.intel.com>
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On Thu, 06 Jun 2024 08:37:31 -0500, chenridong <chenridong@huawei.com>  
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