lkml.org 
[lkml]   [2021]   [Jan]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: rpc_xprt_debugfs_register() - atomic_inc_return() usage
From
Date
On 1/21/21 10:56 AM, Trond Myklebust wrote:
> On Wed, 2021-01-20 at 16:52 -0700, Shuah Khan wrote:
>> Hi Anna and Trond,
>>
>> I came across the following while reviewing atomic_inc_return()
>> usages
>> that cast return value to unsigned
>>
>> rpc_xprt_debugfs_register()'s atomic_inc_return() usage looks a bit
>> odd.
>>
>> - cur_id isn't initialized
>> - id = (unsigned int)atomic_inc_return(&cur_id);
>>
>> Please note that id is int. Is it expected that cur_id could
>> overflow?
>> Is there a maximum limit for this value?
>>
>
> Yes, we do expect cur_id to eventually overflow (once you have created
> 2 billion RPC client instances), however the atomic increment
> operations are expected to handle this correctly according to the
> maintainers (I already asked them in a different context). Furthermore,
> the code itself doesn't care about strict sequentiality. All it wants
> from the counter is uniqueness, with that uniqueness condition actually
> being enforced by the subsequent debugfs_create_file() call.
>
> IOW: I don't think this is a real problem.
>

Great. Thank you for a detailed explanation.

-- Shuah

\
 
 \ /
  Last update: 2021-01-21 19:03    [W:0.032 / U:0.160 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site