[ Home | Alpha index | Topic index | Tutorials | Download | Feedback ]

The OS/2 API Project


[ Syntax | Params | Returns | Include | Usage | Structs | Gotchas | Code | Also ]


rc = DosWaitEventSem( hevSemaphore, ulTimeOut );


HEV hevSemaphore (input)
The handle of the semaphore wait on.

ULONG ulTimeout (input)
The number of milliseconds the function will wait before returning.


The following values can be returned
0NO_ERRORSuccessfully waited for the event semaphore to be posted to
6ERROR_INVALID_HANDLEError, The value in phevSemaphore does not point to a valid semaphore, The calling process must first have access to the semaphore in question
8ERROR_NOT_ENOUGH_MEMORYError, The system memory limit has been exhausted
95ERROR_INTERRUPTError, The thread has become unblocked by an external event such as an exception, ownership has not been obtained
640ERROR_TIMEOUTError, The caller was blocked for ulTimeout milliseconds but no post was issued within this time limit, Time has expired

Include Info

#include <os2.h>

Usage Explanation

DosWaitEventSem blocks until the specified event semaphore is posted.

Event semaphores are edge-triggered. This means that if the semaphore is posted and reset before a waiting thread has a chance to run, the waiting thread will still act as though the semaphore is posted.

Relevant Structures


The process calling DosWaitEventSem must first obtain access to the semaphore in question or ERROR_INVALID_HANDLE will be returned.

If the thread to be blocked, waiting on an event semaphore, is a PM thread, WinWaitEventSem should be used instead of DosWaitEventSem. This will allow the message queue thread to continue processing.

Sample Code

#define INCL_DOSSEMAPHORES #include <os2.h> HEV hevMySemaphore; /* MySemaphore handle */ ULONG TimeOut= -1; /* the number of milliseconds the */ /* the caller will block for the sem */ /* this example will block forever */ /* access is gained to the semaphore in question */ /* either by DosCreateEventSem ... */ /* ... or by DosOpenEventSem */ /* its handle is placed in hevMySemaphore */ rc = DosWaitEventSem(hevMySemaphore, TimeOut); if (rc != 0) { /* We got an error to take care of. */ }

See Also

DosCloseEventSem, DosCreateEventSem, DosOpenEventSem, DosPostEventSem DosQueryEventSem, DosResetEventSem, WinWaitEventSem


Joe Phillips - jaiger@eng2.uconn.edu


Last modified June 19/1996
Please send all errors, comments, and suggestions to: timur@vnet.ibm.com

The OS/2 API Project