IY45273: GETLINE() BLOCKING ALL OTHER THREADS

APAR status

• Closed as fixed if next.

Error description

• PROBLEM DESCRIPTION:
  .
  The customer's testcase contains several threads, a main thread
  that asks for input from the user, and several other threads
  that act independently of the main thread.  The secondary
  threads go through a loop 1000 times printing to the screen and
  sleeping the thread. The secondary threads are simulating
  a server, performing tasks in the background, completely
  independent of what is going on in the main thread.
  .
  The problem is that with C++ V5 and V6 on both AIX 4.3.3 and 5,
  the thread that asks the user for input is locking all of the
  other threads while it waits for input from the user. This
  prevents all of the other threads from executing.
  .
  If the method of getting input from the user is changed from
  getline() to scanf(), the problem goes away; The secondary
  threads continue to execute while the main thread waits for
  input from the user.
  .
  This problem is not present on Linux using our VAC++ 6.0 for
  Linux compiler.
  .
  TESTCASE:
  .
  ******************************* t.C *************************
  #include <sstream>
  #include <pthread.h>
  #include <stdio.h>
  #include <unistd.h>
  #include <syslog.h>
  #include <iostream>
  .
  extern "C" void* func(void* iValue)
  {
    int lID = (int) iValue;
    for(int i = 0; i < 1000; i ++)
      {
        // this line will be blocked by the std::cin.getline()
        std::wstringstream lStream;
  .
        printf("Thread %d >>>  before sleeping...\n", lID);
        sleep(1);
        printf("Thread %d <<< after sleeping...\n", lID);
        sleep(1);
      }
    pthread_exit(0);
    return (void*) 0;
  .
  }
  .
  main()
  {
  .
     pthread_t thread[5];
  .
      for(int i =0; i < 5 ; i ++)
        pthread_create(&thread[i], NULL, func,(void*) i);
  .
      for(int i = 0; i< 100; i ++)
        {
          sleep(1);
          char lString[200];
          printf("Read:\n");
          // this function will wait for user input,
          // AND block other ios constructors
  //        scanf("%s\n",&lString);
          std::cin.getline(lString, 200);
          printf("Got %s\n", lString);
        }
  .
      sleep(100);
  }
  ******************************* t.C ***********************
  .
  COMPILE COMMAND:
  .
  xlC_r t.C
  .
  ACTUAL OUTPUT:
  .
  on AIX:
  .
  $ aix.out
  Thread 0 >>>  before sleeping...
  Thread 1 >>>  before sleeping...
  Thread 2 >>>  before sleeping...
  Thread 3 >>>  before sleeping...
  Thread 4 >>>  before sleeping...
  Thread 0 <<< after sleeping...
  Thread 1 <<< after sleeping...
  Thread 2 <<< after sleeping...
  Thread 3 <<< after sleeping...
  Thread 4 <<< after sleeping...
  Read:
  .
  on Linux:
  .
  jromano@speeder:/home/jromano/pmr/91517> linux.out
  Thread 0 >>>  before sleeping...
  Thread 1 >>>  before sleeping...
  Thread 2 >>>  before sleeping...
  Thread 3 >>>  before sleeping...
  Thread 4 >>>  before sleeping...
  Read:
  Thread 0 <<< after sleeping...
  Thread 1 <<< after sleeping...
  Thread 2 <<< after sleeping...
  Thread 3 <<< after sleeping...
  Thread 4 <<< after sleeping...
  Thread 0 >>>  before sleeping...
  Thread 1 >>>  before sleeping...
  Thread 2 >>>  before sleeping...
  Thread 3 >>>  before sleeping...
  Thread 4 >>>  before sleeping...
  <CTRL-C to kill application>
  .
  EXPECTED OUTPUT:
  .
  The customer expects to see the getline() not to stop all
  threads while it waits for input. The expected output is seen on
  out Linux compiler, as well as on AIX when the getline() is
  changed to scanf().
  

Local fix

Problem summary

• same as submitter's text
  

Problem conclusion

Temporary fix

• no temp fix.
  

Comments

APAR Information

• APAR is sysrouted FROM one or more of the following:

• APAR is sysrouted TO one or more of the following:

Modules/Macros

•    DEFSRXXX
  

Fix information

Applicable component levels