RFR: 8354523: runtime/Monitor/SyncOnValueBasedClassTest.java triggers SIGSEGV [v3]

[Roman Kennke]

> When DiagnoseSyncOnValueBasedClasses is != 0, then we can take the slow-path without having cleared the monitor cache in the BasicLock. This would later lead to a crash or other unexpected behaviour. This can happen with C1 or the interpreter, C2 has the DiagnoseSyncOnValueBasedClasses-block after clearing the cache, and the native-entry in sharedRuntime_x86_64.cpp does not have a DiagnoseSyncOnValueBasedClasses-block at all.
> 
> The proposed fix so far is a bit ugly because it repeats the clearing code in 3 places. The alternative would be to move the DiagnoseSyncOnValueBasedClasses-block into MA::lightweight_lock(), but this would bring DiagnoseSyncOnValueBasedClasses-handling into the native entry in sharedRuntime_x86_64.cpp, which is currently not the case. Also, we don't have enough regs for that, but we can probably use rscratch1 now that 32-bit is gone (as is already done in C1 and interpreter paths anyway).
> 
> I'd first settle on the structure, and then implement the same thing for aarch64.
> ping @xmas92

Roman Kennke has updated the pull request incrementally with one additional commit since the last revision:

  Move DiagnoseSyncOnValueBasedClasses handling into MA::lightweight_lock()

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/24660/files
  - new: https://git.openjdk.org/jdk/pull/24660/files/56006f3e..373a5114

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=24660&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=24660&range=01-02

  Stats: 42 lines in 5 files changed: 19 ins; 22 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/24660.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24660/head:pull/24660

PR: https://git.openjdk.org/jdk/pull/24660