mads1980 opened a new pull request #246: OpenSSLEngine improvements to guard against multiple shutdown() calls triggered by construction exception and finalize() later URL: https://github.com/apache/tomcat/pull/246 We started getting random SIGSEGV JVM crashes on our servers after upgrading to OpenJDK 13.0.2 The crashes are always in tcnative code, on the JVM Finalizer daemon thread, at OpenSSLEngine.shutdown(). We're on Tomcat 9.0.31, tcnative 1.2.23, OpenSSL 1.1.1d and APR 1.7.0 using NIO connectors. This combination works fine with Oracle JDK 8u202 as well as OpenJDK 8u242, but crashes began immediately after upgrading to OpenJDK 13.0.2 Since the failure is related to tcnative code and finalization, we guess the new JVM is probably invoking the finalizers sooner, so this is exposing a bug in OpenSSLEngine which was already present, but was not being triggered on previous JVMs because of different timing. The crash occurs when SSL.freeSSL() is invoked, so this probably means either the pointer is zero, or a double SSL.freeSSL() is invoked. This can happen if there are uncaught exceptions within the OpenSSLEngine constructor, as finalization can execute concurrently with object construction. We adapted the solution found in OpenSSLContext.destroy() which evidently was causing similar issues. The current volatile "destroyed" checks found in OpenSSLEngine seem to be insufficient, so we replaced it with an AtomicBoolean. Also, we check whether "networkBIO" and "ssl" are zero in shutdown() to avoid attempting to free a null pointer. We found a discussing regarding these issues in the following thread: http://mail-archives.apache.org/mod_mbox/tomcat-dev/201901.mbox/%[email protected]%3E It seems the improvements made it to OpenSSLContext but not OpenSSLEngine. This pull request should fix remaining issues. See attached sample HotSpot error dumps. [hs_err_pid28766.log](https://github.com/apache/tomcat/files/4219652/hs_err_pid28766.log) [hs_err_pid32426.log](https://github.com/apache/tomcat/files/4219653/hs_err_pid32426.log)
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