Hello everyone, Thank you Fabian and Friedrich, your comments are highly appreciated, I am following them. Now I have done with eCos thread extension for EDF support. I can build my eCos library and link it to my application successfully. But there is one problem, when I run my application in x86 Advantech board, it "hangs up" without any output after thread creation (with an extended properties). In my void cyg_user_start(void) function I have these lines: printf("Now thread extended with tree more properties\n"); printf("Running with EDF scheduler\n"); cyg_mutex_init(&cliblock); cyg_thread_create(4, simple_program, (cyg_addrword_t) 0, "Thread A", (void *) stack[0], 4096, &simple_threadA, &thread_s[0], 11, 12, 13); cyg_thread_create(4, simple_program, (cyg_addrword_t) 1, "Thread B", (void *) stack[1], 4096, &simple_threadB, &thread_s[1], 21, 22, 23); printf("Created threads with extended properties\n"); cyg_thread_resume(simple_threadA); cyg_thread_resume(simple_threadB); Here 11,12,13 (and 21,22,23) are deadline, wcet, period of the first (second) thread respectively. In my application output I have > Now thread extended with tree more properties; > Running with EDF scheduler only. Application does not output "Created threads with extended properties", which I think to be error. Actually, I am recording each of my modification to eCos repository in PPT file (which I have enclosed here http://rapidshare.com/files/338010937/eCos_EDF_implementation_-_2.pdf.html ) and I have my application code also attached. Can anyone have a look and give me idea, why it is hanging up. One more question is, there are kernel tests in eCos repository, are they to check eCos kernel after such a modification? Thank you in advance! Regards, Nodir.