T-Kernel Specification (1.B0.02)

4.8. INTERRUPT MANAGEMENT FUNCTIONS 189
[Additional Notes]
tk ret int is a system call that does not return to the context from which it was called. Even if an
error code is returned when an error of some kind is detected, normally no error checking is performed
in the context from which the system call was invoked, leaving the possibility that the program will
hang. For this reason these system calls do not return even if error is detected.
Using an assembly-language return (REIT) instruction instead of tk ret int to exit the interrupt handler
is possible if it is clear no dispatching will take place on return from the handler (the same task is
guaranteed to continue executing), or if there is no need for dispatching to take place.
Depending on the CPU architecture and method of configuring the OS, it may be possible to perform
delayed dispatching even when an interrupt handler exits using an assembly-language REIT instruction.
In such cases it is allowable for the assembly-language REIT instruction to be interpreted as if it were a
tk ret int system call.
Performing of E CTX error checking when tk ret int is called from a time event handler is implementationdependent.
Depending on the implementation, control may return from a different type of handler.
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T-Kernel 1.B0.02