Hi Sebastian, > > In all the successful loops the lines in the trace look like the lines in the successful > (2nd) example below. > > In the error case there is an additional sched_waking and sched_wakeup in the > trace. > > Also there is always "prev_state=S" within the forked process. > > In the error case, there is "prev_state=T|K". > > That T|K is probably some kind of debug state the program remains until the > debugger puts it back on track. I think the interesting part ist figure out what decided > to send this signal or put the program into stop-state. Usually a breakpoint, invalid > opcode, … causes this kind of action but my understanding is that you use none of > those. Perhaps I was not precise enough in my previous mail. The effect that I described in there was not a SIGSTOP but a hanging thread. I had to press CTRL-C to interrupt the execution and to enter the gdb prompt. This hanging occurs in 10-20% of the runs. Also here, this hang always occurs when one of the threads does a kind of "clone". And this effect only appears it the kernel is configured for "full preemptible". So there are two effects I have noticed: - The strange SIGSTOP where I cannot provide a simple test executable - The strange issue with the hanging thread (please use the example from my previous mail) In both issues, a "clone" is executed in one of the threads. Regards Mathias ��.n��������+%������w��{.n�����{�����ǫ���ܨ}���Ơz�j:+v�����w����ޙ��&�)ߡ�a����z�ޗ���ݢj��w�f