c - PCRE pcre_exec 线程安全吗？

Question

我有一个 C 程序，它使用 PCRE 正则表达式来确定 cgroup 中的进程是否应添加到一个变量或另一个变量。我生成一个线程来读取每个正在运行的 cgroup 中的 cpuacct.stat 文件，其中线程数从未超过核心数。然后将这些样本和结果组合成两个变量之一。

相关代码片段是:

    pcreExecRet = pcre_exec(reCompiled,
                        pcreExtra,
                        queue,
                        strlen(queue),          // length of string
                        0,                      // Start looking at this point
                        0,                      // OPTIONS
                        subStrVec,
                        30);                    // Length of subStrVec

    //CRITICAL SECTION?
    pthread_mutex_lock(&t_lock); //lock mutex
    while (sumFlag == 0) {
        pthread_cond_wait(&ok_add, &t_lock); //wait on ok signal
    }

    if(pcreExecRet > 0) {
        sumOne += loadavg;
    } else if (pcreExecRet == PCRE_ERROR_NOMATCH){
        sumTwo += loadavg;
    } else {
        perror("Could not determine sum!\n"); //if this fails

    }

    sumFlag = 1;

    pthread_cond_signal(&ok_add); //signal that it is ok to add
    pthread_mutex_unlock(&t_lock); //unlock mutex

我的问题是 pcre_exec() 调用是否是线程安全的？是否应该将其移至临界区？我知道编译的正则表达式是线程安全的，但我不确定 pcreExtra (const pcre_extra) 或 subStrVec (int *ovector)。这些变量目前是全局的。

Answer 1

是的，它是线程安全的，所有PCRE函数都是线程安全的，但在某些情况下你应该小心

以下内容来自manual pages for PCRE

MULTITHREADING

   The PCRE functions can be used in  multi-threading  applications,  with
   the  proviso  that  the  memory  management  functions  pointed  to  by
   pcre_malloc, pcre_free, pcre_stack_malloc, and pcre_stack_free, and the
   callout  and  stack-checking  functions  pointed to by pcre_callout and
   pcre_stack_guard, are shared by all threads.

   The compiled form of a regular expression is not altered during  match-
   ing, so the same compiled pattern can safely be used by several threads
   at once.

   If the just-in-time optimization feature is being used, it needs  sepa-
   rate  memory stack areas for each thread. See the pcrejit documentation
   for more details.