RFR: 8339648: ZGC: Division by zero in rule_major_allocation_rate [v3]

[Matthias Baesken]

> The HS jtreg test gc/stringdedup/TestStringDeduplicationAgeThreshold_ZGenerational
> shows this error when running with ubsan enabled 
> 
> src/hotspot/share/gc/z/zDirector.cpp:491:74: runtime error: division by zero
>     #0 0x7f09886401d4 in rule_major_allocation_rate src/hotspot/share/gc/z/zDirector.cpp:491
>     #1 0x7f09886401d4 in start_gc src/hotspot/share/gc/z/zDirector.cpp:822
>     #2 0x7f09886401d4 in ZDirector::run_thread() src/hotspot/share/gc/z/zDirector.cpp:912
>     #3 0x7f098c1404e8 in ZThread::run_service() src/hotspot/share/gc/z/zThread.cpp:29
>     #4 0x7f09897cac19 in ConcurrentGCThread::run() src/hotspot/share/gc/shared/concurrentGCThread.cpp:48
>     #5 0x7f098bb46b0a in Thread::call_run() src/hotspot/share/runtime/thread.cpp:225
>     #6 0x7f098b1a9881 in thread_native_entry src/hotspot/os/linux/os_linux.cpp:858

Matthias Baesken has updated the pull request incrementally with one additional commit since the last revision:

  add parentheses

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/20888/files
  - new: https://git.openjdk.org/jdk/pull/20888/files/21fe3ca7..6902026f

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=20888&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=20888&range=01-02

  Stats: 2 lines in 1 file changed: 1 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/20888.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20888/head:pull/20888

PR: https://git.openjdk.org/jdk/pull/20888