OpenJDK: Do not block signals - #19
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JamVM blocks SIGQUIT, SIGINT and SIGPIPE in all threads. In the GNU Classpath port, a dedicated signal thread consumes SIGQUIT and SIGINT via sigwait(). SIGPIPE is blocked so that writes to broken pipes fail with EPIPE. The OpenJDK backend uses asynchronous signal handlers: JamVM itself handles SIGQUIT for thread dumps, while SIGHUP, SIGINT and SIGTERM are registered by the class library through sun.misc.Signal. Because SIGQUIT and SIGINT are blocked, their handlers are never invoked. As a result, Ctrl-C neither terminates the VM nor runs shutdown hooks, and SIGQUIT does not produce a thread dump. The signal mask also survives exec() and is inherited by processes launched through Runtime.exec() or ProcessBuilder. OpenJDK did not reset it in the posix_spawn() path until OpenJDK 20 (JDK-8234262). Make the signal-mask policy class-library specific: - GNU Classpath keeps blocking SIGQUIT, SIGINT and SIGPIPE as before. - OpenJDK instead ensures that SIGQUIT, SIGHUP, SIGINT, SIGTERM and SIGPIPE are unblocked, and installs a no-op handler for SIGPIPE so that writes to broken pipes remain nonfatal. Unlike a blocked or ignored signal, the SIGPIPE handler is reset to the default across exec() and therefore does not leak into spawned children. Signed-off-by: Guillermo Rodríguez <grodriguez@ingelabs.com>
phvega
approved these changes
Aug 12, 2026
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JamVM blocks SIGQUIT, SIGINT and SIGPIPE in all threads. In the GNU Classpath port, a dedicated signal thread consumes SIGQUIT and SIGINT via sigwait(). SIGPIPE is blocked so that writes to broken pipes fail with EPIPE.
The OpenJDK backend uses asynchronous signal handlers: JamVM itself handles SIGQUIT for thread dumps, while SIGHUP, SIGINT and SIGTERM are registered by the class library through sun.misc.Signal. Because SIGQUIT and SIGINT are blocked, their handlers are never invoked. As a result, Ctrl-C neither terminates the VM nor runs shutdown hooks, and SIGQUIT does not produce a thread dump.
The signal mask also survives exec() and is inherited by processes launched through Runtime.exec() or ProcessBuilder. OpenJDK did not reset it in the posix_spawn() path until OpenJDK 20 (JDK-8234262).
Make the signal-mask policy class-library specific: