RFR: 8271353: PerfDataManager::destroy crashes in VM_Exit

[Yumin Qi]

On Tue, 27 Jul 2021 23:37:58 GMT, Xin Liu <xliu at openjdk.org> wrote:

> This patch check PerfDataManager::_sampled and _constants is NULL. if it is,
> return -1. 
> 
> When the user enables UL `-Xlog:perf+datacreation=debug`, it may crash in
> PerfDataManager::destroy(). The following line will crash when _sampled is NULL.
> 
> 
>   log_debug(perf, datacreation)("Total = %d, Sampled = %d, Constants = %d",
>                                 _all->length(), _sampled->length(), _constants->length());
> 
> 
> This only happens when UsePerfData is on and PerfDataManager::destroy() is invoked before
> StatSampler::initialize() which initializes PerfDataManager::_sampled.
> PerfDataManager::destroy() is called by VM_Exit which can be triggered by SIGINT on Linux anytime.
> 
> A reproducible: invoke the following command and keep pressing Ctrl-c.
> $perf stat -r 100 java -Xlog:perf+datacreation=debug --version

Hi, Xin
  The copyright year needs updated. 
  Maybe '0' is more meaningful than '-1'?

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PR: https://git.openjdk.java.net/jdk/pull/4913