threadCritical_windows.cpp revision 1472
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0N/A
0N/A# include "incls/_precompiled.incl"
0N/A# include "incls/_threadCritical_windows.cpp.incl"
0N/A
0N/A// OS-includes here
0N/A# include <windows.h>
0N/A# include <winbase.h>
0N/A
0N/A//
0N/A// See threadCritical.hpp for details of this class.
0N/A//
0N/A
0N/Astatic bool initialized = false;
0N/Astatic volatile jint lock_count = -1;
0N/Astatic HANDLE lock_event;
0N/Astatic DWORD lock_owner = -1;
0N/A
0N/A//
0N/A// Note that Microsoft's critical region code contains a race
0N/A// condition, and is not suitable for use. A thread holding the
0N/A// critical section cannot safely suspend a thread attempting
0N/A// to enter the critical region. The failure mode is that both
0N/A// threads are permanently suspended.
0N/A//
0N/A// I experiemented with the use of ordinary windows mutex objects
0N/A// and found them ~30 times slower than the critical region code.
0N/A//
0N/A
0N/Avoid ThreadCritical::initialize() {
0N/A}
0N/A
0N/Avoid ThreadCritical::release() {
0N/A assert(lock_owner == -1, "Mutex being deleted while owned.");
0N/A assert(lock_count == -1, "Mutex being deleted while recursively locked");
0N/A assert(lock_event != NULL, "Sanity check");
0N/A CloseHandle(lock_event);
0N/A}
0N/A
0N/AThreadCritical::ThreadCritical() {
0N/A DWORD current_thread = GetCurrentThreadId();
0N/A
0N/A if (lock_owner != current_thread) {
0N/A // Grab the lock before doing anything.
0N/A while (Atomic::cmpxchg(0, &lock_count, -1) != -1) {
0N/A if (initialized) {
0N/A DWORD ret = WaitForSingleObject(lock_event, INFINITE);
0N/A assert(ret == WAIT_OBJECT_0, "unexpected return value from WaitForSingleObject");
0N/A }
0N/A }
0N/A
0N/A // Make sure the event object is allocated.
0N/A if (!initialized) {
0N/A // Locking will not work correctly unless this is autoreset.
0N/A lock_event = CreateEvent(NULL, false, false, NULL);
0N/A initialized = true;
0N/A }
0N/A
0N/A assert(lock_owner == -1, "Lock acquired illegally.");
0N/A lock_owner = current_thread;
0N/A } else {
0N/A // Atomicity isn't required. Bump the recursion count.
0N/A lock_count++;
0N/A }
0N/A
0N/A assert(lock_owner == GetCurrentThreadId(), "Lock acquired illegally.");
0N/A}
0N/A
0N/AThreadCritical::~ThreadCritical() {
0N/A assert(lock_owner == GetCurrentThreadId(), "unlock attempt by wrong thread");
0N/A assert(lock_count >= 0, "Attempt to unlock when already unlocked");
0N/A
0N/A if (lock_count == 0) {
0N/A // We're going to unlock
0N/A lock_owner = -1;
0N/A lock_count = -1;
0N/A // No lost wakeups, lock_event stays signaled until reset.
0N/A DWORD ret = SetEvent(lock_event);
0N/A assert(ret != 0, "unexpected return value from SetEvent");
0N/A } else {
0N/A // Just unwinding a recursive lock;
0N/A lock_count--;
0N/A }
0N/A}