RFR: 8305819: LogConfigurationTest intermittently fails on AArch64

[David Holmes]

On Thu, 4 May 2023 03:04:40 GMT, gaogao-mem <duke at openjdk.org> wrote:

>>> > if we replace the current solution with read/write lock, I guess we won't lose much in terms of performance. but this seems a separated task.
>>> 
>>> Let's do that. Then we'll have code that's known to be correct, and we can all do other things. grin
>> 
>> https://github.com/openjdk/jdk/pull/9838
>> 
>> Here's my old PR for a read-write lock that was meant to replace this RCU mechanism :-). It's a simple counter based one, which I borrowed from ZGC. If anyone wants to pick up this code then feel free to do so (with me as contributor and Oracle copyright notice).
>
> @jdksjolen Could you please integrate #9838 to master and then we can apply the read-write lock in the UL?

The PR was never approved and was somewhat contentious. I would want to see how UL uses the proposed RWL before considering the integration of both changes. This is not a trivial amount of work I know.

Buried on the other PR was a suggestion to switch the broken UL RCU mechanism for one of the other VM RCU-like mechanisms, but I'm not familiar enough with those other mechanisms to say if that is viable. But perhaps the UL RCU mechanism can be examined against those other ones to see if any more bugs are evident?

Or we just proceed with a suitably commented storeStore barrier and hope that this is the last RCU bug.

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PR Review Comment: https://git.openjdk.org/jdk/pull/13421#discussion_r1184627702