tcgetattr() hangs

Kustaa Nyholm Kustaa.Nyholm at
Tue May 29 08:02:51 UTC 2012


this maybe wrong list but I gotta start somewhere.

I'm the developer of PureJavaComm (PJC) , a pure Java serial port access
library that runs on Mac OS X, Linux, Windows and soon I hope on
FreeBSD. I'm co-operating with someone to port the library to
FreeBSD but we have run into mysterious problem that has defeated
all our debugging efforts.

PJC can be found at:

Some background. PJC uses JNA which is a library to access C-code
APIs from Java by writing Java classes that JNA automatically
turns in to standard C calls.

The C functions we are using are very simple and few, here is the complete
list to put you into the picture (btw, this is Java):

 int errno();
 int fcntl(int fd, int cmd, int arg); int cfgetispeed(Termios termios);
 int cfgetospeed(Termios termios);
 int setspeed(int fd, int speed);
 int cfsetispeed(Termios termios, int speed);
 int cfsetospeed(Termios termios, int speed)
 int tcflush(int fd, int b);
 int tcdrain(int fd);
 void cfmakeraw(Termios termios);
 int tcgetattr(int fd, Termios termios);
 int tcsetattr(int fd, int cmd, Termios termios); int tcsendbreak(int fd,
int duration);
 int open(String s, int t); int close(int fd);
 int write(int fd, byte[] buffer, int len);
 int read(int fd, byte[] buffer, int len);
 int ioctl(int fd, int cmd, int[] data);
 int select(int n, FDSet read, FDSet write, FDSet error, TimeVal timeout);

So far we have been able to run PJC testsuite in FreeBSD 32 bit Intel with
no problems. 

Now however, on FreeBSD 64 bit AMD our test set hangs in a call to
in the third test case in our test suite.

The first test opens a port and wiggles some control lines, then closes
the port.
The second test sends and receives a some hundreds of messages using a
thread and select(). This is the test that is causing problem further down
the line.
After this test the next test (regardless what it is) hangs in a call to
after successfully opening the port.

So how can tcgetattr() hang???

I found one reference to a similar problem but no solution:

Here is a piece of our debug log that shows the calls from Java to the
API showing the end of the successful Test2 and the hang at the beginning
of Test3:

log: > select(9,[8],[],[],jtermios.TimeVal at 6f507fb2)
.................................. OK average speed log: <
select(9,[],[],[],jtermios.TimeVal at 6f507fb2) => 0
log: > select(9,[8],[],[],jtermios.TimeVal at 6f507fb2)
18241 b/sec at baud rate 19200
log: > fcntl(8, 3, 0)
log: < fcntl(8, 3, 0) => 2
log: > fcntl(8, 4, 6)
log: < fcntl(8, 4, 6) => 0
log: > close(8)
log: < close(8) => 0
Test3 - transmit all characters     log: <
select(9,[8],[],[],jtermios.TimeVal at 6f507fb2) => -1
log: > open('cuau0',00008006)
log: < open('cuau0',00008006) => 8
log: > close(8)
log: < close(8) => 0
log: > open('cuau0',00008006)
log: < open('cuau0',00008006) => 8
log: > fcntl(8, 3, 0)
log: < fcntl(8, 3, 0) => 6
log: > fcntl(8, 4, 2)
log: < fcntl(8, 4, 2) => 0
log: > tcgetattr(8,jtermios.Termios at 5a77a7f9)

All comments welcome.

be Kusti

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