pSOSystem System Calls - Read

t_create pSOS+ System Calls
Target
flags Specifies the task’s attributes. flags is formed by OR-ing the
following symbolic constants (one from each pair), which are defined
in . For instance, to specify that a task is global, you place
the symbolic constant T_GLOBAL in flags. To specify that the task is
global and uses the FPU processor, you place both T_GLOBAL and
T_FPU in flags, using the following syntax:
T_GLOBAL | T_FPU
T_GLOBAL /
T_LOCAL
T_FPU /
T_NOFPU
Using sstack and ustack
Makes the task global: external tasks on other nodes
can address it / restricts the task to the local node.
The T_GLOBAL attribute is ignored by the singleprocessor
kernel.
Informs the pSOS+ kernel that the task uses /does
not use the FPU coprocessor (see “Using the T_FPU
Flag” under “Target.”)
tid Points to the variable where t_create() stores the task ID assigned
to the task.
On most processors, a task can execute only in supervisor mode. Thus, a task can
have only a supervisor stack. On these processors ustack is added to sstack to
create a supervisor stack of the combined sizes. Exceptions to this usage are shown
below.
68K
CF
PPC
On 68K processors, a task can execute in either user mode or supervisor
mode. A user stack is not needed if the task never executes in the user
mode, in which case ustack should be set to 0. If the task starts in the
user mode, then ustack must be greater than 20 bytes. The supervisor/
user mode is set in the t_start() system call.
On ColdFire and PowerPC processors, a task can execute in either user
mode or supervisor mode, but there are not separately defined stacks
depending on this mode. t_create() simply adds sstack and ustack
together and allocates a stack of that resultant size.
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