Messages in this thread | | | Date | Mon, 28 Mar 2011 15:13:27 -0700 | From | Darren Hart <> | Subject | Re: PROBLEM:a bug about pi-futex maybe let the program going to hang |
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On 03/28/2011 01:26 AM, Peter Zijlstra wrote: > On Mon, 2011-03-28 at 15:25 +0800, xby wrote: >> hi, all. > > Works better if you also CC people who actually work on that code. > >> Maybe, there is a bug about pi-futex, it would let the program in user-space going to hang. >> >> We have a board: CPU is powerpc 8572, two core. after ran one month, the state of pi-futex in user-space got bad: mutex->__data.__lock is 0x8000023e, mutex->__data.__count is 0, mutex->__data.__owner is 0. >> >> then, I review file "kernel/funtex.c"(the version is linux 2.6.38), found a case: >> >> if there are 3 thread, named threadA, threadB, threadC。thread A hold mutexM, threadB and threadC is waiting mutexM. They run as fllow steps: >> >> 1. threadB and threadC sleep at line 1984. >> 2. threadB receive a signal, then it will be wake up. >> 3. threadA unlock mutexM, and give mutexM to threadB. >> 4. threadB call fixup_owner, try to give mutex to threadC. >> 5. at line 1580, threadB trigger a addr-fault, then goto handle_fault. >> 6. at line 1617, threadB release spinlock, then handle fault. >> 7. threadC got spinlock, and call fixup_owner, and got mutexM. >> 8. threadC give mutexM to threadB. >> 9. threadB re-got spinlock, it will found "pi_state->owner == oldowner" and retry to fixup. >> 10. threadB give mutexM to threadC, that's a bad thing. >> >> we have wrote a program, this program can prove all above. > > It would have been ever so much more useful if you'd have included that.
Please reply with the testcase and your glibc version please. If this is a custom kernel, please make your .config as well.
-- Darren Hart Intel Open Source Technology Center Yocto Project - Linux Kernel -- 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/
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