RFR: 8268361: Fix the infinite loop in next_line [v3]

[UncleNine]

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

UncleNine has updated the pull request incrementally with one additional 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/c055e977..3d50b052

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=4378&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=4378&range=01-02

  Stats: 11 lines in 1 file changed: 8 ins; 0 del; 3 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