[jdk17] RFR: 8269865: Async UL needs to handle ERANGE on exceeding SEM_VALUE_MAX [v2]

[David Holmes]

On Tue, 6 Jul 2021 08:06:17 GMT, Xin Liu <xliu at openjdk.org> wrote:

>> This patch solved the sempahore overflow issue with errno ERANGE or EOVERFLOW.
>> Previously, we have asymmetric p/v operations for semaphore _sem. Each iteration
>> only decrements _sem 1 but dequeues N messages. If logging threads keep preempting
>> async logging thread, it may cause the value of _sem accumulates until overflow! 
>> 
>> The patch corrects the value of _sem after write(). n messages are dequeued/processed.
>> We need to invoke _sem.wait() max(n-1, 1) time. This ensures that each iteration
>> decrements n instead of 1.
>
> Xin Liu has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Fix build issue on Windows and simplify the loop.

I don't like the idea of trying to limit the log size based on a platform specific private implementation detail - and you'd have to check that against any user supplied buffer size and reject a too large buffer.

The other option is revert these changes and expose a way to ignore the ERANGE error in Semaphore.

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PR: https://git.openjdk.java.net/jdk17/pull/216