One of the primary difficulties that result from using static variables in multi-threaded
computer programs is that changes to a static variable made by one thread will
be seen by all other threads operating within the same process. Multiple threads
cannot use static variables separately because other threads within the process
can overwrite the values stored at the variable memory location. Thus, the development
of multi-threaded programs using static variables often requires explicit thread
harmonization by the programmer. Another problem is that threads within the same
process must use unique static variable IDs to avoid reading or writing to the
location of another static variable. This also requires thread harmonization by
the programmer. Accordingly, in view of the shortcomings associated with existing
thread-static data implementations, there remains a need for an efficient thread-static
data implementation that can be used on most modern operating systems. The present
invention provides embodiments of a method, data processing system, and computer
program product that efficiently implements thread-static data without registering
pointers. The present invention efficiently implements static thread data in a
multi-threaded program. The static thread data of each thread is allocated to the
top of the virtual memory block belonging to the corresponding stack of each thread.
An address mask is created for each thread so as to extract the base address of
the static thread data region of the stack for each thread from the corresponding
stack pointer. When a thread in execution needs to access its static thread data,
it accesses the static thread data variable according to the virtual memory address
extracted from the stack pointer using the address mask.
