DosExitCritSec
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 can enter and exit 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;
}
