Uploaded image for project: 'WiredTiger'
  1. WiredTiger
  2. WT-7899

WT_SESSION::strerror is not thread-safe

    XMLWordPrintable

    Details

    • Type: Bug
    • Status: Needs Scheduling
    • Priority: Minor - P4
    • Resolution: Unresolved
    • Affects Version/s: WT3.2.1, WT10.0.0
    • Fix Version/s: None
    • Component/s: None
    • Labels:
      None

      Description

      We would like to ask clarification about the "thread-safe" property of WT_SESSION::strerror function.

       

      In the documentation of wiredtiger_strerror there is a note about that the WT_SESSION::strerror maybe thread-safe (both for 3.2.1 and 10.0.1):
      (see WT_SESSION::strerror for a thread-safe API).
      https://source.wiredtiger.com/develop/group__wt.html#gae8bf720ddb4a7a7390b70424594c40fd
      https://source.wiredtiger.com/3.2.1/group__wt.html#gae8bf720ddb4a7a7390b70424594c40fd

       

      In the implementation of WT_SESSION::strerror there is a direct call of wiredtiger_strerror. Because of that the WT_SESSION::strerror seems to be not thread-safe.

       

      In os_errno.c:

      const char *
      __wt_strerror(WT_SESSION_IMPL *session, int error, char *errbuf, size_t errlen)
      {
          const char *p;
       
          /*
           * Check for a WiredTiger or POSIX constant string, no buffer needed.
           */
          if ((p = __wt_wiredtiger_error(error)) != NULL)
              return (p);
      

       

      An example code that demonstrates the problem is the following:

       
      #include <stdio.h>
      #include <pthread.h>
      #include <string.h>
      #include "wiredtiger.h"
       
      WT_CONNECTION *conn = NULL;
       
      void *thread(void *args) {
          int r = 0;
          WT_SESSION *thread_session = NULL;
          r = conn->open_session(conn, NULL, NULL, &thread_session);
          printf("thread wiredtiger_session: %d\n", r);
       
          const char *s = thread_session->strerror(thread_session, 2000);
          printf("thread s: %p : %s\n", s, s);
          return NULL;
      }
       
      int main() {
          WT_SESSION *main_session = NULL;
       
          int r = 0;
          r = wiredtiger_open("WT_HOME", NULL, "create", &conn);
          printf("wiredtiger_open: %d\n", r);
       
          r = conn->open_session(conn, NULL, NULL, &main_session);
          printf("main wiredtiger_session: %d\n", r);
       
          const char *s = main_session->strerror(main_session, 3000);
       
          pthread_t t;
          pthread_create(&t, NULL, thread, NULL);
          pthread_join(t, NULL);
       
          printf("main   s: %p : %s\n", s, s);
       
          conn->close(conn, NULL);
          return 0;
      }
      
      

      Output:

      wiredtiger_open: 0
      main wiredtiger_session: 0
      thread wiredtiger_session: 0
      thread s: 0xa0f460 : Unknown error 2000
      main   s: 0xa0f460 : Unknown error 2000
      
      

      Note that both error strings are the same. If the WT_SESSION::strerror is thread-safe then the expected behavior would be to get the two different error strings ( "Unknown error 2000" and " Unknown error 3000").

        Attachments

          Activity

            People

            Assignee:
            keith.bostic Keith Bostic
            Reporter:
            akristo.jetapps@gmail.com akos kristo
            Votes:
            0 Vote for this issue
            Watchers:
            3 Start watching this issue

              Dates

              Created:
              Updated: