Fix process-wide signal handler override in JNI_OnLoad#632
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rfcom wants to merge 1 commit intoFazecast:masterfrom
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Fix process-wide signal handler override in JNI_OnLoad#632rfcom wants to merge 1 commit intoFazecast:masterfrom
rfcom wants to merge 1 commit intoFazecast:masterfrom
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JNI_OnLoad called sigaction() to set SIGUSR1 and SIGUSR2 to SIG_IGN, overwriting the JVM's signal chain process-wide without saving the previous handler (third argument NULL instead of &oldAction). On Linux, JavaScriptCore (WebKit) uses SIGUSR1 to suspend threads during garbage collection: the GC thread sends SIGUSR1 via pthread_kill to all threads, and each thread's handler calls sem_post to acknowledge. With SIG_IGN, the acknowledgement never arrives and the GC thread waits indefinitely, causing a permanent hang in any JavaFX WebView application that uses jSerialComm. Remove all sigaction() calls from JNI_OnLoad. Replace with per-thread pthread_sigmask() calls in the two event reader threads, which blocks only the signals that could interrupt serial port I/O in those specific threads without affecting the rest of the process. SIGUSR1 and SIGUSR2 are intentionally NOT blocked. These threads must remain suspendable by the JVM GC — blocking them would prevent garbage collection from working on those threads. The other signals (SIGHUP, SIGTTOU, SIGTTIN) are also unnecessary process-wide because serial ports are opened with O_NOCTTY, which prevents them from becoming the controlling terminal. Fixes Fazecast#631
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JNI_OnLoad called sigaction() to set SIGUSR1 and SIGUSR2 to SIG_IGN, overwriting the JVM's signal chain process-wide without saving the previous handler (third argument NULL instead of &oldAction).
On Linux, JavaScriptCore (WebKit) uses SIGUSR1 to suspend threads during garbage collection: the GC thread sends SIGUSR1 via pthread_kill to all threads, and each thread's handler calls sem_post to acknowledge. With SIG_IGN, the acknowledgement never arrives and the GC thread waits indefinitely, causing a permanent hang in any JavaFX WebView application that uses jSerialComm.
Remove all sigaction() calls from JNI_OnLoad. Replace with per-thread pthread_sigmask() calls in the two event reader threads, which blocks only the signals that could interrupt serial port I/O in those specific threads without affecting the rest of the process.
SIGUSR1 and SIGUSR2 are intentionally NOT blocked. These threads must remain suspendable by the JVM GC — blocking them would prevent garbage collection from working on those threads.
The other signals (SIGHUP, SIGTTOU, SIGTTIN) are also unnecessary process-wide because serial ports are opened with O_NOCTTY, which prevents them from becoming the controlling terminal.
Fixes #631