> On Mar 23, 2016, at 7:39 PM, Yan, Zheng <zyan@xxxxxxxxxx> wrote:
>
>
>> On Mar 23, 2016, at 23:39, Douglas Fuller <dfuller@xxxxxxxxxx> wrote:
>>
>>
>>> +#define ceph_try_get_string(x) \
>>> +({ \
>>> + struct ceph_string *___str; \
>>> + rcu_read_lock(); \
>>> + ___str = rcu_dereference(x); \
>>> + if (___str && !kref_get_unless_zero(&___str->kref)) \
>>> + ___str = NULL; \
>>> + rcu_read_unlock(); \
>>> + (___str); \
>>
>> Isn’t this an unsafe use of __str? As I understand it, it could be updated after rcu_read_unlock().
>
> where does it get updated?
By a later RCU update. As I understand it, an rcu_dereference()d pointer is only guaranteed stable inside rcu_read_lock()/rcu_read_unlock().
>
> Regards
> Yan, Zheng
>
>>
>>> +})
>>
>
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