User-Level Native Thread Primitives (GThread) Library White Paper (G06.26+)

User-Level Native Thread Primitives (GThread Library) 03/31/2005
Hewlett-Packard Company--540065-001 Page 26 of 46
2.10. Saving and Restoring Stacks
GTH_STACK_SAVE_( GThread_CB cb )
Description:
Performs a copy (save) of the current thread’s runtime stack as part of suspending current thread
execution (dispatching another thread). Callable only for a swapped thread. This replaces accessing
the thread control block elements SwapArea, StackStart, StackUsed, and performing the copy of
the stack to the save area from the runtime stack area.
Input:
cb - The address of the current thread control block.
Return: int16
Returns zero if save completed successfully. nonzero indicates the copy failed due to a static thread
model, a discontiguous swap area, or insufficient swap space.
Considerations:
This routine must be called after GTHREAD_SETJMP_ or by a function passed to be called by
GTHREAD_SETJMP_. See sections 3.2 and 3.6.3.1. The routine does not validate whether the
thread control block supplied belongs to the currently executing thread. If the control block of a
suspended thread is provided, corruption of the specified thread’s runtime environment occurs.
GTH_STACK_RESTORE_( GThread_CB cb )
Description:
Performs a restore of the target thread’s runtime stack as part of dispatching that thread. Callable
only for a swapped thread. This replaces accessing the thread control block elements SwapArea,
StackStart, StackUsed, and performing the copy of the stack from the save area back to the runtime
stack area.
Input:
cb - The address of the target thread control block whose stack needs to be restored.
Return: int16
Returns zero if restore completed successfully. nonzero indicates the restore failed due to a static
thread model or a discontiguous swap area.
Considerations:
The routine does not validate that the thread control block supplied belongs to the currently
executing thread. If the control block of a suspended thread is provided, corruption of the specified
thread’s runtime environment occurs. This interface has the same requirements as the original
approach where the client performed the restoration function manually – the interface must be called
within the target routine specified in a call to GTHREAD_SWAPIN_SETUP_.