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Date:   Mon, 6 Mar 2023 16:36:04 -0800
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Subject: Re: [PATCH bpf-next v3 1/8] bpf: Maintain the refcount of struct_ops
 maps directly.
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To:     Kui-Feng Lee <sinquersw@gmail.com>, Kui-Feng Lee <kuifeng@meta.com>
Cc:     bpf@vger.kernel.org, ast@kernel.org, song@kernel.org,
        kernel-team@meta.com, andrii@kernel.org, sdf@google.com
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From:   Martin KaFai Lau <martin.lau@linux.dev>
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On 3/6/23 3:54 PM, Kui-Feng Lee wrote:
>>> @@ -646,6 +679,7 @@ const struct bpf_map_ops bpf_struct_ops_map_ops = {
>>>       .map_alloc_check = bpf_struct_ops_map_alloc_check,
>>>       .map_alloc = bpf_struct_ops_map_alloc,
>>>       .map_free = bpf_struct_ops_map_free,
>>> +    .map_free_rcu = bpf_struct_ops_map_free_rcu,
>>
>> just came to my mind. Instead of having a rcu callback, synchronize_rcu() can 
>> be called in bpf_struct_ops_map_free(). Then the '.map_free_rcu' addition and 
>> its related change is not needed.
>>
> 
> synchronize_rcu() probably blocks other subsystem, right?

.map_free is called from system_unbound_wq, so it can block.