RFR: 8292695: SIGQUIT and jcmd attaching mechanism does not work with signal chaining library [v2]

[Xin Liu]

On Thu, 8 Sep 2022 02:41:56 GMT, Man Cao <manc at openjdk.org> wrote:

>> Hi all,
>> 
>> Could anyone review this bug fix? See https://bugs.openjdk.org/browse/JDK-8292695 for details.
>> 
>> I changed the temporary handler for SIGQUIT to use a dummy function, and use `os::signal()` to set it up, just as `os::initialize_jdk_signal_support()` does.
>> It is possible that just moving the `set_signal_handler(BREAK_SIGNAL, false);` in `install_signal_handlers()` outside of the window bounded by `JVM_{begin|end}_signal_setting()` could also fix this bug. However, `set_signal_handler()` and `JVM_HANDLE_XXX_SIGNAL()` are currently used for signals that support chaining and periodically check, which do not apply to SIGQUIT. I think it is cleaner to use different functions for SIGQUIT.
>> 
>> I also added a test to check that sending SIGQUIT should produce a thread dump on stdout, with and without using libjsig.so.
>> 
>> -Man
>
> Man Cao has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains four additional commits since the last revision:
> 
>  - Merge branch 'master' into JDK-8292695
>  - Install SIGBREAK handler only once
>  - Fix whitespace
>  - 8292695: SIGQUIT and jcmd attaching mechanism does not work with signal chaining library

I try it out. yeah, it works! One installation but it will remember early SIGBREAK.

Why do you insist to move jdk_misc_signal_init() before install_signal_handlers()? Is there any difference before and after it?

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