RFR: 8271348: Add stronger sanity check of thread state when polling for safepoint/handshakes [v2]

Fri Jul 30 00:08:56 UTC 2021

On Thu, 29 Jul 2021 23:42:33 GMT, Daniel D. Daugherty <dcubed at openjdk.org> wrote:

>> src/hotspot/share/runtime/safepoint.cpp line 716:
>> 
>>> 714:   // So we can miss this poll, but stop at next.
>>> 715: 
>>> 716:   // Load dependent store, it must not pass loading of safepoint_id.
>> 
>> Existing: I struggle to understand what this comment means - we are storing the value of safepoint_id so I don't see how the loading of safepoint_id can be reordered. ???
>
> I'll have to check to see who added that comment.

It was added here:

commit bec8431683a36ad552a15cd7c4d5ca48058249a7
Author: Robbin Ehn <rehn at openjdk.org>
Date:   Fri Feb 15 14:15:10 2019 +0100

    8203469: Faster safepoints

    Reviewed-by: dcubed, pchilanomate, dholmes, acorn, coleenp, eosterlund

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PR: https://git.openjdk.java.net/jdk/pull/4936