Messages in this thread | | | From | "Ming Lei" <> | Subject | can linux RT thread corrupt global variable? | Date | Mon, 5 May 2003 13:52:18 -0700 |
| |
Platform: Intel Pentium II; RedHat 7.2 with kernel version 2.4.7-10, libc 2.2.4-13 and gcc 2.96.
Problem description:
a program has a thread of priority 12, a thread of priority 10, a thread of priority 6, and the main process at priority 0. All the threads except main process is created with pthread_create, and defined SCHED_FIFO as real time scheduler policy.
There is a global variable I define as 'int cpl'. All the threads and main process may alter cpl at any time. cpl may have one of these values {0, 0xf000006e, 0xf0000068, 0xe0000000, 0xe0000060}.
<Problem=> at some point of execution which cpl should be a value say e0000060, but the actual value retained at cpl is another say e0000000; that is, the value is changed without the program actually done anything on it. The retained value I observed is kind of historic value(one of these value in the above set), not the arbituary value. The problem had occured just after context switch, also occured during a thread execution.
<Confirm> I used Intel debug register to track any writing to the cpl memory address globally, which is the way GDB use for x86 hardware watchpoint implementation. I could see all the writing from my program to change cpl, but failed to see the source from which the problem occured. So I dont know what cause the problem.
Can anyone listening give me a direction or hint on this annoying situation? Any help is thanked here.
PS. please cc to this email address. -Ming
Related questions:
Is linux kernel 2.4.10 considered strictly preemptive such as VxWorks or other RTOS? I guess 2.4.10 may simulate preemptive with running scheduler on every syscall or interrupt returns. Am I right?
Is printf() real-time priority thread safe?
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |