Pavel Emelianov wrote:
> Balbir Singh wrote:
>> Pavel Emelianov wrote:
>>>> +static inline bool res_counter_check_under_limit(struct res_counter *cnt)
>>>> +{
>>>> + bool ret;
>>>> + unsigned long flags;
>>>> +
>>>> + spin_lock_irqsave(&cnt->lock, flags);
>>>> + ret = res_counter_limit_check_locked(cnt);
>>> We don't have to take the lock for such a check.
>>>
>>
>> This check without the lock could be racy and return incorrect
>> results -- leading to OOM.
>
> Maybe. Nevertheless, if we do not trust the return value of
> try_to_free_pages() then the code should probably look like
>
> while (1) {
> if (res_counter_charge() == 0)
> break;
>
> did_progress = try_to_free_pages();
> if (res_counter_charge() == 0)
> break;
>
> if (!did_progress)
> out_of_memory();
> }
>
Yes, this looks better.
> But in any case we must know for sure was at least one page
> freed or not...
>
> Thanks,
> Pavel
--
Warm Regards,
Balbir Singh
Linux Technology Center
IBM, ISTL
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