RFR: Fixed two string dedup issues

[Zhengyu Gu]

Okay, will add to comments.

-Zhengyu


On 10/10/2017 01:43 PM, Aleksey Shipilev wrote:
> On 10/10/2017 07:35 PM, Zhengyu Gu wrote:
>> safepoint test does not tell us if we are evacuating objects in parallel phase or concurrent phase,
>> where we have to deal with differently. For shenandoah specific safepoints, we know dedup thread is
>> suspended, can safely queue strings.
> 
> Ah! So here is the most important bit which deserves to be in the comment!
> 
>     // SafepointSynchronize::is_at_safepoint() is not sufficient, because generic safepoints
>     // that might happen during concurrent evacuation are not suspending the deduplication thread,
>     // and pushes to the dedup queue are unsafe.
> 
> -Aleksey
>