RFR: 8292695: SIGQUIT and jcmd attaching mechanism does not work with signal chaining library [v3]

[Man Cao]

On Thu, 8 Sep 2022 08:47:40 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:

>> Man Cao has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Move jdk_misc_signal_init() earlier and clarify its comment
>
> src/hotspot/os/posix/signals_posix.cpp line 1319:
> 
>> 1317:     // Also note that HotSpot does NOT support signal chaining for BREAK_SIGNAL.
>> 1318:     // Applications that require a custom BREAK_SIGNAL handler should run with
>> 1319:     // -XX:+ReduceSignalUsage. Otherwise if libjsig is used together with
> 
> Maybe also mention "AllowUserSignalHandlers"

The SIGBREAK handler does not seem to honor `-XX:+AllowUserSignalHandlers`. It is still installed even with `-XX:+AllowUserSignalHandlers`.

Perhaps it can be addressed separately later? As commented in https://bugs.openjdk.org/browse/JDK-8293466, I haven't seen a real use case for +AllowUserSignalHandlers, so I'd vote for deprecating `AllowUserSignalHandlers` for removal in the future.

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