SyncCtl(), SyncCtl_r()

Perform an operation on a synchronization object

Don't use the SyncCtl() or SyncCtl_r() kernel call directly; instead, call one of the following:
Instead of this cmd: Call:
_NTO_SCTL_GETPRIOCEILING pthread_mutex_getprioceiling()
_NTO_SCTL_SETPRIOCEILING pthread_mutex_setprioceiling()
_NTO_SCTL_SETEVENT SyncMutexEvent()
_NTO_SCTL_MUTEX_WAKEUP pthread_mutex_wakeup_np()

Synopsis:

#include <sys/neutrino.h>

int SyncCtl( int cmd,
             sync_t * sync,
             void * data );

int SyncCtl_r( int cmd,
               sync_t * sync,
               void * data );

Arguments:

cmd
The operation type; one of:
  • _NTO_SCTL_GETPRIOCEILING — get the ceiling priority of the mutex pointed to by sync and put it in the variable pointed to by data.
  • _NTO_SCTL_SETPRIOCEILING — return the original ceiling priority. Set the ceiling priority of the mutex pointed to by sync to the value pointed to by data.
  • _NTO_SCTL_SETEVENT — attach an event, pointed to by data, to the mutex pointed to by sync.
  • _NTO_SCTL_MUTEX_WAKEUP — wake up threads that are blocked on a mutex. The data argument points to a structure that specifies the process and thread IDs.
sync
A pointer to the synchronization object that you want to manipulate.
data
A pointer to data associated with the command, or a place where the function can store the requested information, depending on the operation.

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

Description:

The SyncCtl() and SyncCtl_r() kernel calls let you:

  • set or get a ceiling priority for a mutex
  • attach an event to a mutex so you'll be notified when the mutex changes to the DEAD state
  • wake up threads that are blocked on a mutex

These functions are similar, except for the way they indicate errors. See the Returns section for details.

  • In order to change the priority ceiling to a value above the maximum permitted for unprivileged processes, your process must have the PROCMGR_AID_PRIORITY ability enabled.
  • In order to attach to a mutex an event that sends a pulse, your process must have the PROCMGR_AID_CONNECTION ability enabled.

For more information, see procmgr_ability() .

Returns:

The only difference between these functions is the way they indicate errors:

SyncCtl()
If an error occurs, the function returns -1 and sets errno . Any other value returned indicates success.
SyncCtl_r()
Returns EOK on success. This function does NOT set errno. If an error occurs, the function returns any value listed in the Errors section.

Errors:

EAGAIN
All kernel synchronization event objects are in use.
EFAULT
A fault occurred when the kernel tried to access sync or data.
EINVAL
The synchronization object pointed to by sync doesn't exist, or the ceiling priority value pointed to by data is out of range.
ENOSYS
The SyncCtl() and SyncCtl_r() functions aren't currently supported.
EPERM
The calling process doesn't have the required permission; see procmgr_ability() .

Classification:

QNX Neutrino

Safety:
Cancellation point No
Interrupt handler No
Signal handler Yes
Thread Yes

Related links