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

[Thomas Stuefe]

On Thu, 8 Sep 2022 21:38:14 GMT, Man Cao <manc at openjdk.org> wrote:

>> 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.

Okay for separate addressing. Deprecating may not be an option though, depending on how seriously we take backward compatibility.

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