RFR: 8370044: TraceBytecodes shouldn't break up lines [v2]

[Paul Hübner]

> Hi all, 
> 
> This patch addresses bytecodes being torn/mangled when printing concurrently (i.e., tracing the bytecodes of concurrently executing threads). Taking `invokeinterface` on `foo` as an example, the output could look something like the following two, ranging from mangled but legible to completely illegible:
> 
> jint[27651] [27395]   696080    64  invokeinterface,  116 <CoherentBytecodeTraceTest$Strategy.foo(I)V> 
> 
> 
> [43267]   696692    64  invokeinterface
> )
> [33283] [27395] [27907]   696694    29  fast_agetfield 116 <CoherentBytecodeTraceTest$Strategy.foo(I)V> 
> 
> 
> The solution is to buffer each bytecode print into a `stringStream` before giving it to the tty. This avoids having to take a tty lock. With this solution, the print looks as follows (note: different occurrence so surrounding bytecodes differ):
> 
> [25347]   685730    61  iconst_1
> [25091]   685717    64  invokeinterface 190 <CoherentBytecodeTraceTest$Strategy.foo(I)V> 
> [24579]   685732    20  invokestatic 125 <java/util/concurrent/ConcurrentHashMap.spread(I)I> 
> [24579]   685734    23  istore #4
> 
> 
> I introduce a test case that finds `<CoherentBytecodeTraceTest$Strategy.foo(I)V>` and ensures the bytecode preceding it is correct. This reliably failed every time previously, and does not fail after my change.
> 
> Parsing the code, I noticed that bytecode printing takes a parameter `bool buffer = true` which internally buffer to a `stringStream` before flushing to the provided `outputStream`. There were numerous places where the calling code was performing buffering itself without passing `buffer = false`, effectively double buffering. This has been addressed.
> 
> Testing: tiers 1-4. on Linux (x64, AArch64), macOS (x64, AArch64), Windows (x64).

Paul Hübner has updated the pull request incrementally with one additional commit since the last revision:

  Johan's feedback.

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/29842/files
  - new: https://git.openjdk.org/jdk/pull/29842/files/11d7f951..ebcc73b9

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=29842&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=29842&range=00-01

  Stats: 23 lines in 1 file changed: 10 ins; 6 del; 7 mod
  Patch: https://git.openjdk.org/jdk/pull/29842.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29842/head:pull/29842

PR: https://git.openjdk.org/jdk/pull/29842