Question

我使用“ valgrind --tool = drd…”在C语言中调试了基于POSIX pthread的程序。Valgrind检测到错误，并使用以下错误消息终止了线程：

drd: drd_vc.c:96 (vgDrd_vc_increment): Assertion 'oldcount < vc->vc[i].count' failed.

host stacktrace:
==27993==    at 0x38025C68: ??? (in /usr/lib64/valgrind/drd-amd64-linux)
==27993==    by 0x38025D94: ??? (in /usr/lib64/valgrind/drd-amd64-linux)
==27993==    by 0x38025F21: ??? (in /usr/lib64/valgrind/drd-amd64-linux)
==27993==    by 0x38018317: ??? (in /usr/lib64/valgrind/drd-amd64-linux)
==27993==    by 0x380183EC: ??? (in /usr/lib64/valgrind/drd-amd64-linux)
==27993==    by 0x380187FC: ??? (in /usr/lib64/valgrind/drd-amd64-linux)
==27993==    by 0x3801D87E: ??? (in /usr/lib64/valgrind/drd-amd64-linux)
==27993==    by 0x3800967A: ??? (in /usr/lib64/valgrind/drd-amd64-linux)
==27993==    by 0x3803DB80: ??? (in /usr/lib64/valgrind/drd-amd64-linux)
==27993==    by 0x38078BDF: ??? (in /usr/lib64/valgrind/drd-amd64-linux)
==27993==    by 0x3808742A: ??? (in /usr/lib64/valgrind/drd-amd64-linux)

sched status:
  running_tid=1

Thread 1: status = VgTs_Runnable (lwpid 27993)
==27993==    at 0x4C339D3: pthread_mutex_unlock (in /usr/lib64/valgrind/vgpreload_drd-amd64-linux.so)
==27993==    by 0x47F671: lf_pthread_mutex_unlock (htab2.c:192)
==27993==    by 0x405194: prepare_to_read_n_go (ep3.c:805)
==27993==    by 0x4053C4: reading_begin (ep3.c:847)
==27993==    by 0x405CFF: start_file_loader (ep3.c:1062)
==27993==    by 0x405D4E: start_services (ep3.c:1076)
==27993==    by 0x406743: init_procs (ep3.c:1295)
==27993==    by 0x40336B: main (ep.c:89)

在程序源代码中，“ lf_pthread_mutex_unlock”中的系统调用“ pthread_mutex_unlock”是终止之前执行的最后一条语句。我正在使用包装有``Linux linux 4.4.76-1-default＃1 SMP Fri Jul 14 08:48:13 UTC 2017（9a2885c）x86_64 x86_64 x86_64 GNU / Linux''的OpenSuse。编译器为gcc-4.8。

我在drd_vc.c中找到了源代码：

/** Increment the clock of thread 'tid' in vector clock 'vc'. */
void DRD_(vc_increment)(VectorClock* const vc, DrdThreadId const tid)
{
   unsigned i;
   for (i = 0; i < vc->size; i++)
   {
      if (vc->vc[i].threadid == tid)
      {
         typeof(vc->vc[i].count) const oldcount = vc->vc[i].count;
         vc->vc[i].count++;
         // Check for integer overflow.
         tl_assert(oldcount < vc->vc[i].count);
         return;
      }
   }
   …
}

其中的语句“ tl_assert（oldcount vc [i] .count）;”是转折点。

我不明白线程计数器“ count”的含义是什么，以及它如何在程序中溢出。我的程序正在运行大量数据（数百万条记录）。我用不同数量的变量更改了程序，并注意到错误始终发生。因此，我猜该错误不是由内存覆盖引起的。

有关源代码drd_vc.c的性质的任何信息将不胜感激。谢谢。

valgrind drd_vc.c中的POSIX pthread计数器（整数）溢出

0 个答案: