The scope of an NSPR thread, specified as a parameter to PR_CreateThread or returned by PR_GetThreadScope.
#include <prthread.h>
typedef enum PRThreadScope {
PR_LOCAL_THREAD,
PR_GLOBAL_THREAD
PR_GLOBAL_BOUND_THREAD
} PRThreadScope;
PR_LOCAL_THREADPR_GLOBAL_THREADPR_GLOBAL_BOUND_THREADAn enumerator of type PRThreadScope specifies how a thread is scheduled: either locally by NSPR within the process (a local thread) or globally by the host (a global thread).
Global threads are scheduled by the host OS and compete with all other threads on the host OS for resources. They are subject to fairly sophisticated scheduling techniques.
Local threads are scheduled by NSPR within the process. The process is assumed to be globally scheduled, but NSPR can manipulate local threads without system intervention. In most cases, this leads to a significant performance benefit.
However, on systems that require NSPR to make a distinction between global and local threads, global threads are invariably required to do any form of I/O. If a thread is likely to do a lot of I/O, making it a global thread early is probably warranted.
On systems that don't make a distinction between local and global threads, NSPR silently ignores the scheduling request. To find the scope of the thread, call PR_GetThreadScope.