DosExitCritSec

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Restores normal thread dispatching for the current process.

Syntax

DosExitCritSec ( )

Parameters

none

Return Code

ulrc (APIRET) - returns

DosExitCritSec returns one of the following values:

  • 0 NO_ERROR
  • 309 ERROR_INVALID_THREADID
  • 485 ERROR_CRITSEC_UNDERFLOW

Remarks

DosExitCritSec is used following DosEnterCritSec to restore normal thread switching to the threads of a process.

A count is maintained of the number of times DosEnterCritSec is issued without a corresponding DosExitCritSec. The count is incremented by DosEnterCritSec, and decremented by DosExitCritSec. Normal thread dispatching is not restored until the count is zero.

The outstanding count is maintained in a word. If an underflow occurs (the count is decremented below zero), the count is set to zero, no operation is performed, and the request returns with ERROR_CRITSEC_UNDERFLOW.

ERROR_INVALID_THREADID is returned when an invalid attempt is made to exit a critical section of code in a signal handler or exception handler.

ERROR_INVALID_THREADID is also returned when a dynamic link library (DLL) routine incorrectly issues DosExitCritSec.

Example Code

This example shows how a thread enters and exits a critical section of code.

#define INCL_DOSPROCESS      /* Process values */
#define INCL_DOSERRORS       /* Error values */
#include <os2.h>
#include <stdio.h>

int main(VOID)
{
  APIRET  rc = NO_ERROR;    /* Return code */

  rc = DosEnterCritSec();

  if (rc != NO_ERROR) {
      printf("DosEnterCritSec error: return code = %u\n",rc);
      return 1;
  }
    /***********************************************/
    /* Add critical section code here.  While this */
    /* code is running, all other threads are      */
    /* stopped.  CALL NO LIBRARY OR OS/2 FUNCTIONS */
    /* HERE UNLESS YOU KNOW THEY DO NOT REQUIRE    */
    /* ACTION BY ANOTHER THREAD IN THE PROCESS.    */
    /***********************************************/

  rc =  DosExitCritSec();

  if (rc != NO_ERROR) {
      printf("DosExitCritSec error: return code = %u\n",rc);
      return 1;
  }

  return NO_ERROR;
}

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