RFR: JDK-8288556: VM crashes if it gets sent SIGUSR2 from outside

[Thomas Stuefe]

On Mon, 20 Jun 2022 08:02:36 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:

> Another issue, I tried the patch with redefining SR_SIGNUM and found that I could not use SIGUSR1 on Linux because its numerical value (10) is below SIGSEGV(11) on my box and we have this code:
> 
> https://urldefense.com/v3/__https://github.com/openjdk/jdk/blob/0a5f5770612cd8523ff0c16b240faf8498b94043/src/hotspot/os/posix/signals_posix.cpp*L1684-L1689__;Iw!!ACWV5N9M2RV99hQ!Ndl79VsW_OfatocPfBl3W4JtFwX05nUiQiF5X9ovSXN8OcN9CYDFM0WV-Zv-BZ6FWbQeLgffH2UKn8FQefxdsk3QCjmw$ 
> 
> Do you think this is fix-worthy? SIGUSR1 seems an obvious choice for an alternate SR signal, but OTOH nobody complained in 20+ years.

I read up on this in the very good analysis at: https://bugs.openjdk.org/browse/JDK-4355769?focusedCommentId=12425929&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#comment-12425929 . This was a wild read :) I continue to be impressed by the quality of bug reports in JBS.

Seems more complicated than I thought. I am not sure how much of this is till valid today. This was 21 years ago. I'm surprised by the described behaviour though, that SIGUSR2 can interrupt delivery of error signals; I would have naively thought that signal delivery is on a strict first come first deliver base.

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PR: https://git.openjdk.org/jdk/pull/9181