RFR: 8268361: Fix the infinite loop in next_line [v4]

[UncleNine]

> If the /proc/stat mount point is changed in container environment, the while loop may lead to 100% cpu usage.

UncleNine has refreshed the contents of this pull request, and previous commits have been removed. The incremental views will show differences compared to the previous content of the PR. The pull request contains one new commit since the last revision:

  8268361: Fix the infinite loop in next_line

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/4378/files
  - new: https://git.openjdk.java.net/jdk/pull/4378/files/3d50b052..e4f90ebd

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=4378&range=03
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=4378&range=02-03

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4378.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4378/head:pull/4378

PR: https://git.openjdk.java.net/jdk/pull/4378