取消pthread_cond_wait（）与PRIO_INHERIT互斥体挂起 [英] Cancelling pthread_cond_wait() hangs with PRIO_INHERIT mutex

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问题描述

更新，2012年4月4日：
修复了libc补丁





我在取消 pthread_cond_wait ，它们使用具有 PTHREAD_PRIO_INHERIT 属性集的互斥体。



以下最小示例演示了这一点：（使用 g ++< filename>。编译.cpp -lpthread ）

  #include< pthread.h> 
 #include< iostream> 
 
 pthread_mutex_t mutex; 
 pthread_cond_t cond 
 
 void clean（void * arg）{
 std :: cout< clean：Unlocking mutex ...< std :: endl; 
 pthread_mutex_unlock（（pthread_mutex_t *）arg）; 
 std :: cout<< clean：Mutex unlocked ...< std :: endl; 
} 
 
 void * threadFunc（void * arg）{
 int ret = 0; 
 pthread_mutexattr_t mutexAttr; 
 ret = pthread_mutexattr_init（& mutexAttr）; std :: cout<< ret =< ret<< std :: endl; 
 
 //注释掉以下行，一切正常。
 ret = pthread_mutexattr_setprotocol（& mutexAttr，PTHREAD_PRIO_INHERIT）; std :: cout<< ret =< ret<< std :: endl; 
 
 ret = pthread_mutex_init（& mutex，& mutexAttr）; std :: cout<< ret =< ret<< std :: endl; 
 ret = pthread_cond_init（& cond，0）; std :: cout<< ret =< ret<< std :: endl; 
 
 std :: cout<< threadFunc：Init done，entering wait ...< std :: endl; 
 
 pthread_cleanup_push（clean，（void *）& mutex）; 
 ret = pthread_mutex_lock（& mutex）; std :: cout<< ret =< ret<< std :: endl; 
 while（1）{
 ret = pthread_cond_wait（& cond，& mutex）; std :: cout<< ret =< ret<< std :: endl; 
} 
 pthread_cleanup_pop（1）; 
 
 return 0; 
} 
 
 int main（）{
 pthread_t thread; 
 int ret = 0; 
 ret = pthread_create（& thread，0，threadFunc，0）; std :: cout<< ret =< ret<< std :: endl; 
 
 std :: cout<< main：Thread created，waiting a bit ...< std :: endl; 
 sleep（2）; 
 
 std :: cout<< main：Canceling threadFunc ...< std :: endl; 
 ret = pthread_cancel（thread）; std :: cout<< ret =< ret<< std :: endl; 
 
 std :: cout<< main：Joining threadFunc ...< std :: endl; 
 ret = pthread_join（thread，NULL）; std :: cout<< ret =< ret<< std :: endl; 
 
 std :: cout<< main：JoinlineFunc，done！ << std :: endl; 
 return 0; 
}



每次运行时， main / code>挂起在 pthread_join（）。 gdb backtrace显示以下内容：

 线程2（线程0xb7d15b70（LWP 257））：
＃0 0xb7fde430 __kernel_vsyscall（）
＃1 0xb7fcf362在__lll_lock_wait（）at ../nptl/sysdeps/unix/sysv/linux/i386/i686/../i486/lowlevellock.S:142 
＃2 0xb7fcc9f9 __condvar_w_cleanup（）at ../nptl/sysdeps/unix/sysv/linux/i386/i686/../i486/pthread_cond_wait.S:434 
＃3 0x08048fbe在threadFunc（arg = 0x0）at / home / pthread_cond_wait .cpp：22 
＃4 0xb7fc8ca0在pthread_create.c中的start_thread（arg = 0xb7d15b70）：301 
＃5 0xb7de73ae在clone（）at ../sysdeps/unix/sysv/linux/i386/clone .S：130 
 
线程1（线程0xb7d166d0（LWP 254））：
＃0 0xb7fde430在__kernel_vsyscall（）
＃1 0xb7fc9d64在pthread_join（threadid = 3083950960，thread_return = 0x0）at pthread_join.c：89 
＃2 0x0804914a在main（）at /home/pthread_cond_wait.cpp:41

如果在互斥体上没有设置 PTHREAD_PRIO_INHERIT ，一切都会正常工作，程序会完全退出。



有问题的平台：




  • 嵌入式AMD融合板，运行基于PTXDist 的32位Linux 3.2.9-rt16（带有 RTpatch 16）。我们正在使用最新的 OSELAS i686交叉工具链（2011.11.1），使用gcc

  • 与2011.03.1工具链同样的板子（gcc 4.5.2 / glibc 2.13 / binutils 2.18 / kernel 2.6.36）。



没有问题的平台：




  • 我们自己的ARM板，也运行一个PTXDist Linux（32位2.6.29.6-rt23），使用OSELAS arm-v4t交叉工具链（1.99.3）与gcc 4.3.2 / glibc 2.8 / binutils 2.18 / kernel 2.6.27。

  • 我的笔记本电脑（Intel Core i7）运行64位Ubuntu 11.04（虚拟化/内核2.6.38.15通用），gcc 4.5.2 / eglibc 2.13-0ubuntu13.1 / binutils 2.21 .0.20110327。



我一直在寻找解决方案的网络，并遇到了一些我试过的补丁，没有任何效果：





我们做错了在我们的代码中，这恰恰是在某些平台上工作，或者是底层系统中的一个错误？如果有人知道在哪里看，或知道任何补丁或类似的尝试，我很高兴听到这个。



谢谢！ p>

更新：




解决方案

这已由 libc patch 。
我已经确认它在我自己有问题的平台（我们的定制的AMD融合板）上工作，修补到glibc-2.14.1。



给Siddhesh Poyarekar修复！


Update, 4/10 2012: Fixed by libc patch

I have a problem canceling threads in pthread_cond_wait, that use mutexes with the PTHREAD_PRIO_INHERIT attribute set. This only happens on certain platforms though.

The following minimal example demonstrates this: (compile with g++ <filename>.cpp -lpthread)

#include <pthread.h>
#include <iostream>

pthread_mutex_t mutex;
pthread_cond_t cond;

void clean(void *arg) {
    std::cout << "clean: Unlocking mutex..." << std::endl;
    pthread_mutex_unlock((pthread_mutex_t*)arg);
    std::cout << "clean: Mutex unlocked..." << std::endl;
}

void *threadFunc(void *arg) {
    int ret = 0;
    pthread_mutexattr_t mutexAttr;
    ret = pthread_mutexattr_init(&mutexAttr); std::cout << "ret = " << ret << std::endl;

    //Comment out the following line, and everything works
    ret = pthread_mutexattr_setprotocol(&mutexAttr, PTHREAD_PRIO_INHERIT); std::cout << "ret = " << ret << std::endl;

    ret = pthread_mutex_init(&mutex, &mutexAttr); std::cout << "ret = " << ret << std::endl;
    ret = pthread_cond_init(&cond, 0); std::cout << "ret = " << ret << std::endl;

    std::cout << "threadFunc: Init done, entering wait..." << std::endl;

    pthread_cleanup_push(clean, (void *) &mutex);
    ret = pthread_mutex_lock(&mutex); std::cout << "ret = " << ret << std::endl;
    while(1) {
        ret = pthread_cond_wait(&cond, &mutex); std::cout << "ret = " << ret << std::endl;
    }
    pthread_cleanup_pop(1);

    return 0;
}

int main() {
    pthread_t thread;
    int ret = 0;
    ret = pthread_create(&thread, 0, threadFunc, 0); std::cout << "ret = " << ret << std::endl;

    std::cout << "main: Thread created, waiting a bit..." << std::endl;
    sleep(2);

    std::cout << "main: Cancelling threadFunc..." << std::endl;
    ret = pthread_cancel(thread); std::cout << "ret = " << ret << std::endl;

    std::cout << "main: Joining threadFunc..." << std::endl;
    ret = pthread_join(thread, NULL); std::cout << "ret = " << ret << std::endl;

    std::cout << "main: Joined threadFunc, done!" << std::endl;
    return 0;
}

Every time I run it, main() hangs on pthread_join(). A gdb backtrace shows the following:

Thread 2 (Thread 0xb7d15b70 (LWP 257)):
#0  0xb7fde430 in __kernel_vsyscall ()
#1  0xb7fcf362 in __lll_lock_wait () at ../nptl/sysdeps/unix/sysv/linux/i386/i686/../i486/lowlevellock.S:142
#2  0xb7fcc9f9 in __condvar_w_cleanup () at ../nptl/sysdeps/unix/sysv/linux/i386/i686/../i486/pthread_cond_wait.S:434
#3  0x08048fbe in threadFunc (arg=0x0) at /home/pthread_cond_wait.cpp:22
#4  0xb7fc8ca0 in start_thread (arg=0xb7d15b70) at pthread_create.c:301
#5  0xb7de73ae in clone () at ../sysdeps/unix/sysv/linux/i386/clone.S:130

Thread 1 (Thread 0xb7d166d0 (LWP 254)):
#0  0xb7fde430 in __kernel_vsyscall ()
#1  0xb7fc9d64 in pthread_join (threadid=3083950960, thread_return=0x0) at pthread_join.c:89
#2  0x0804914a in main () at /home/pthread_cond_wait.cpp:41

If PTHREAD_PRIO_INHERIT isn't set on the mutex, everything works as it should, and the program exits cleanly.

Platforms with problems:

  • Embedded AMD Fusion board, running a PTXDist based 32-bit Linux 3.2.9-rt16 (with RTpatch 16). We are using the newest OSELAS i686 cross toolchain (2011.11.1), using gcc 4.6.2, glibc 2.14.1, binutils 2.21.1a, kernel 2.6.39.
  • Same board with the 2011.03.1 toolchain also (gcc 4.5.2 / glibc 2.13 / binutils 2.18 / kernel 2.6.36).

Platforms with no problems:

  • Our own ARM-board, also running a PTXDist Linux (32-bit 2.6.29.6-rt23), using OSELAS arm-v4t cross toolchain (1.99.3) with gcc 4.3.2 / glibc 2.8 / binutils 2.18 / kernel 2.6.27.
  • My laptop (Intel Core i7), running 64-bit Ubuntu 11.04 (virtualized / kernel 2.6.38.15-generic), gcc 4.5.2 / eglibc 2.13-0ubuntu13.1 / binutils 2.21.0.20110327.

I have been looking around the net for solutions, and have come across a few patches that I've tried, but without any effect:

Are we doing something wrong in our code, which just happens to work on certain platforms, or is this a bug in the underlying systems? If anyone has any idea about where to look, or knows of any patches or similar to try out, I'd be happy to hear about it.

Thanks!

Updates:

解决方案

This has been fixed by a libc patch. I've confirmed it to work on my own problematic platform (our custom AMD Fusion board), patched onto glibc-2.14.1.

Thanks go out to Siddhesh Poyarekar for the fix!

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