RFR: 8368089: G1: G1PeriodicGCTask::should_start_periodic_gc may use uninitialised value if os::loadavg is unsupported [v5]

[Thomas Schatzl]

On Wed, 24 Sep 2025 14:50:23 GMT, Guanqiang Han <ghan at openjdk.org> wrote:

>> Please review this change. Thanks!
>> 
>> **Description:**
>> 
>> Previously the check combined loadavg() failure and threshold comparison in a single condition. When os::loadavg() returned -1, `recent_load` contained an undefined value but was still logged as if it was a real load average, leading to misleading log output.
>> 
>> **Fix:**
>> 
>> This change separates the failure case from the combined check:
>> - If os::loadavg() returns -1, log "System loadavg not supported" and skip.
>> - Only compare `recent_load` to the threshold when loadavg() succeeds.
>> 
>> **Test:**
>> 
>> GHA
>
> Guanqiang Han has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Update g1PeriodicGCTask.cpp
>   
>   The periodic gc would be started the first time after detecting that loadavg is not supported.

Marked as reviewed by tschatzl (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/27413#pullrequestreview-3266502208