8370715: JFR: Races are possible when dumping recordings

[roberttoyonaga]

Summary

This PR changes the JFR snapshot dumping code so that multiple JFR recordings (potentially from different processes) racing to write the same dump destination won't mix their data.

Problem

The dump destination file is created and/or wiped when a recording is started, but not wiped again before actually copying over the chunks during a dump. So in the window of time between creating/wiping and dumping chunks, another recording could write to the same dump destination and have it's chunks added to the snapshot. This can happen with either a single JVM or multiple JVMs that are racing.

Proposed fix

This PR ensures that any data previously written to the dump destination is wiped before the new recording's data is written. File locking is also done while chunks are being written.

Testing:

• new test jdk/jdk/jfr/api/recording/dump/TestDumpOverwrite.java
• Tier 1

---

Progress

• Change must be properly reviewed (1 review required, with at least 1 Reviewer)
• Change must not contain extraneous whitespace
• Commit message must refer to an issue

Issue

• JDK-8370715: JFR: Races are possible when dumping recordings (Bug - P4)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk.git pull/28460/head:pull/28460
$ git checkout pull/28460

Update a local copy of the PR:
$ git checkout pull/28460
$ git pull https://git.openjdk.org/jdk.git pull/28460/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 28460

View PR using the GUI difftool:
$ git pr show -t 28460

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk/pull/28460.diff

Using Webrev

Link to Webrev Comment

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[openjdk]

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[mlbridge]

Webrevs

• 01: Full - Incremental (b2ef365d)
• 00: Full (48ec9a7f)