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SchedSet(), SchedSet_r()

Set the scheduling policy for a thread

Synopsis:

#include <sys/neutrino.h>

int SchedSet( 
       pid_t pid,
       int tid,
       int policy,
       const struct sched_param *param );

int SchedSet_r(
       pid_t pid,
       int tid,
       int policy,
       const struct sched_param *param );

Arguments:

pid
0 or a process ID; see below.
tid
0 or a thread ID; see below.
policy
The scheduling policy; one of:

For more information, see Thread scheduling in the QNX Neutrino Microkernel chapter of the System Architecture guide.

param
A pointer to a sched_param structure where the function can store the scheduling parameters.

Library:

libc

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

Description:

The SchedSet() and SchedSet_r() kernel calls set both the scheduling policy and the associated parameters for the thread specified by tid in the process specified by pid. If pid is zero the current process is used to look up a nonzero tid. If tid is zero, then the calling thread is used and pid is ignored.

These functions are identical except in the way they indicate errors. See the Returns section for details.


Note: Instead of using these kernel calls directly, consider calling pthread_setschedparam().

Blocking states

These calls don't block.

Returns:

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

SchedSet()
If an error occurs, -1 is returned and errno is set. Any other value returned indicates success.
SchedSet_r()
EOK is returned on success. This function does NOT set errno. If an error occurs, any value in the Errors section may be returned.

Errors:

EFAULT
A fault occurred when the kernel tried to access the buffers you provided.
EINVAL
The given scheduling policy is invalid.
EPERM
The process doesn't have permission to change the scheduling of the indicated thread.
ESRCH
The process indicated by pid or thread indicated by tid doesn't exist.

Classification:

QNX Neutrino

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

See also:

pthread_setschedparam(), sched_get_priority_max(), sched_get_priority_min(), sched_param, SchedGet(), SchedInfo(), SchedYield()

Thread scheduling in the QNX Neutrino Microkernel chapter of the System Architecture guide

Scheduling algorithms in the Programming Overview chapter of the QNX Neutrino Programmer's Guide


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