[jdk8u-dev] RFR: 8235211: serviceability/attach/RemovingUnixDomainSocketTest.java fails with AttachNotSupportedException: Unable to open socket file [v3]

[Xin Liu]

> Hi, 
> 
> Could you review this backport of 8235211? This is a follow up of JDK-8225690.
> 
> 
> This patch can't be applied to jdk8u cleanly. We replace os::naked_yield with os::yield(), which is available in jdk8u and have same implementations on Linux/BSD/AIX.  Except for that, all other changes are just path adjustment. 
> 
> There's a deadlock in the original backport. Both Signal dispatcher(refer to S for short) and AttachListener(A) are Java Threads.  Therefore, they are subject to safepoint synchronization.
> 
> A sets `_state` to AL_INITIALIZED and then get blocked at a safepoint(maybe AttachListener::dequeue).
> If the socket file is deleted and JVM receive SIGQUIT the, S realizes that the socket file has gone in `check_socket_file` and start to reinitialize it. It falls into this loop and prevent itself from reaching the safepoint.
> 
>      while (AttachListener::transit_state(AL_INITIALIZING,
>                                            AL_NOT_INITIALIZED) != AL_NOT_INITIALIZED) {
>         os::naked_yield();
>       }
> 
> 
> If A waked up and realized that the socket has gone,  it would set `_state` to AL_NOT_INITIALIZED. Current code is adeadlock.  A can’t wake up because S hasn’t reached the safepoint yet. S can’t reach the safepoint because A hasn’t set _state to AL_NOT_INITIALIZED.  This patch avoids the deadlock by trapping into blocked state before the loop.

Xin Liu has updated the pull request incrementally with one additional commit since the last revision:

  fix typo when we manually edited the two test files.
  
  Currently, RemovingUnixDomainSocketTest.java isn't running because @test
  is taken away when we backport JDK-8225690. we try to keep the patch
  intact in case we enable it in the future.

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

Changes:
  - all: https://git.openjdk.java.net/jdk8u-dev/pull/32/files
  - new: https://git.openjdk.java.net/jdk8u-dev/pull/32/files/c9df0828..6f86e099

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk8u-dev&pr=32&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk8u-dev&pr=32&range=01-02

  Stats: 3 lines in 2 files changed: 3 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk8u-dev/pull/32.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk8u-dev pull/32/head:pull/32

PR: https://git.openjdk.java.net/jdk8u-dev/pull/32