RFR: 8292695: SIGQUIT and jcmd attaching mechanism does not work with signal chaining library [v4]

[Man Cao]

On Mon, 24 Oct 2022 07:38:17 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:

> SIGQUIT is semantically a VM signal, owned by the VM, but initialized outside the libjsig-VM-signal-initialization window. The solution proposed by me makes SIGQUIT initialize like any other VM signal, ...

Yes, this is main reason we installed BREAK_SIGNAL handler inside `install_signal_handlers` and reordered `jdk_misc_signal_init` and `install_signal_handlers`.

There was a concern that with libjsig present and without `-Xrs`, user could still install a custom BREAK_SIGNAL handler that overrides JVM's handler, see https://github.com/openjdk/jdk/pull/9955#discussion_r956623350. This change avoids this problem.

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PR: https://git.openjdk.org/jdk/pull/9955