home *** CD-ROM | disk | FTP | other *** search
- /*
- $Id$
- $Log$
- Desc:
- Lang: english
- */
- #include "exec_intern.h"
- #include "semaphores.h"
-
- /*****************************************************************************
-
- NAME */
- #include <exec/semaphores.h>
- #include <clib/exec_protos.h>
-
- __AROS_LH1(void, ObtainSemaphore,
-
- /* SYNOPSIS */
- __AROS_LA(struct SignalSemaphore *, sigSem, A0),
-
- /* LOCATION */
- struct ExecBase *, SysBase, 94, Exec)
-
- /* FUNCTION
- Obtain an exclusive lock on a semaphore. If the semaphore is already
- in use by another task this function will wait until the semaphore
- becomes free.
-
- INPUTS
- sigSem - Pointer to semaphore structure
-
- RESULT
-
- NOTES
- This function preserves all registers.
-
- EXAMPLE
-
- BUGS
-
- SEE ALSO
- ReleaseSemaphore()
-
- INTERNALS
-
- HISTORY
- 29-10-95 digulla automatically created from
- exec_lib.fd and clib/exec_protos.h
- 21-01-96 fleischer implementation
-
- *****************************************************************************/
- {
- __AROS_FUNC_INIT
- __AROS_BASE_EXT_DECL(struct ExecBase *,SysBase)
- struct Task *me;
-
- /* Get pointer to current task */
- me=SysBase->ThisTask;
-
- /* Arbitrate for the semaphore structure */
- Forbid();
-
- /* Check if the semaphore is in use by another task */
- if(sigSem->ss_NestCount&&sigSem->ss_Owner!=me)
- {
- /*
- I wish there was some shared memory available as a semaphore node.
- Unfortunately it isn't - and I cannot rely on being able to get
- some from AllocMem() at this point either, so I have to use a part
- of the stack instead :-(.
- */
- struct SemaphoreNode sn;
-
- sn.node.ln_Pri =SN_TYPE_OBTAIN;
- sn.node.ln_Name=(char *)SM_EXCLUSIVE;
- sn.task =me;
-
- /* Add the node to the semaphore's waiting queue. */
- AddTail((struct List *)&sigSem->ss_WaitQueue,&sn.node);
-
- /* Wait until the semaphore is free */
- Wait(SEMAPHORESIGF);
-
- /* ss_NestCount and ss_Owner are already set by ReleaseSemaphore() */
- }else
- {
- /* The semaphore is free - take it over */
- sigSem->ss_NestCount++;
- sigSem->ss_Owner=me;
- }
-
- /* All done */
- Permit();
- __AROS_FUNC_EXIT
- } /* ObtainSemaphore */
-
-