SIGSEGV (0xb) at [libc.so.6+0x90e1d] pthread_cancel+0x1f

[HanyzPAPU]

Version

2.11.4, Linux/POSIX backend (src/main/c/Posix/SerialPort_Posix.c)

Crash

Top of call stack:

C  [libc.so.6+0x90e1d]  pthread_cancel+0x1f
j  com.fazecast.jSerialComm.SerialPort$SerialPortEventListener.stopListening()V+63
j  com.fazecast.jSerialComm.SerialPort.closePort()Z+18

Triggered by calling closePort() after a USB-serial device is unplugged during an active event listener (e.g. reacting to LISTENING_EVENT_PORT_DISCONNECTED).

Possible cause

eventReadingThread1 and eventReadingThread2 are pthread_detach'd after creation. eventReadingThread1's loop exits on its own when the device disappears, because TIOCMIWAIT starts returning an error and isSupported flips to 0:

isSupported = !ioctl(port->handle, TIOCMIWAIT, mask) && !ioctl(port->handle, TIOCGICOUNT, ...); 

Once that thread returns, its detached pthread_t is invalid, but port->eventsThread1 still holds a dangling reference. eventReadingThread2 stays alive, detects POLLHUP, fires LISTENING_EVENT_PORT_DISCONNECTED. The caller reacts by calling closePort() → stopListening() → setEventListeningStatus(..., false), which does:

if (port->eventsThread1)                                                                                                                                                                                                                                                                                                                              
      pthread_cancel(port->eventsThread1);   // stale detached ref → SIGSEGV inside libc

Per POSIX, using a pthread_t of an already-terminated detached thread is undefined behavior.

Proposed fix

Zero the thread IDs from inside the threads immediately before they return, so the if (port->eventsThreadN) guard in setEventListeningStatus actually means "thread is still alive":

// at the end of eventReadingThread1, just before `return NULL;`                                                                                                                                                                                                                                                                                      
port->eventsThread1 = 0;                                                                                                                                                                                                                                                                                                                              
return NULL;

and likewise in eventReadingThread2. There will still be a race though, completely avoiding it would require not detaching and joining the thread to free up resources.