Replace synchronized block with ReentrantLock to avoid possible thread pinning with virtual threads (Java 21)

[ofaizulin]

It's recommended to avoid using synchronized block with VirtualThreads. Spring Boot starting from 3.2 and other frameworks now allow to run using virtual threads, so it's small, but valuable change for such scenarios.

[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
No data about Duplication

See analysis details on SonarCloud

[mweirauch]

Just for the record:

i7-6820HQ, Fedora 40, 8.0.422-tem; JMX 1.33:

(11.0.24-tem, 17.0.12-tem and 21.0.4-tem with pretty much identical results)

# before

Benchmark                                                          Mode  Cnt        Score         Error   Units
ProcfsStatusBenchmark.collectAverage                               avgt    5       21,530 ±       0,330   ns/op
ProcfsStatusBenchmark.collectAverageContended                      avgt    5       22,660 ±       0,151   ns/op
ProcfsStatusBenchmark.collectSingle                                  ss    5  6020898,400 ± 4289315,078   ns/op

# after

Benchmark                                                          Mode  Cnt        Score         Error   Units
ProcfsStatusBenchmark.collectAverage                               avgt    5       21,517 ±       0,192   ns/op
ProcfsStatusBenchmark.collectAverageContended                      avgt    5       22,576 ±       0,224   ns/op
ProcfsStatusBenchmark.collectSingle                                  ss    5  5290317,400 ± 2752044,273   ns/op

[mweirauch]

Thanks for the contribution @ofaizulin! Sorry it took me so long.