Merge in the new GIL.
diff --git a/Python/ceval_gil.h b/Python/ceval_gil.h
new file mode 100644
index 0000000..2687f95
--- /dev/null
+++ b/Python/ceval_gil.h
@@ -0,0 +1,335 @@
+/*
+ * Implementation of the Global Interpreter Lock (GIL).
+ */
+
+#include <stdlib.h>
+#include <errno.h>
+
+
+/* First some general settings */
+
+/* microseconds (the Python API uses seconds, though) */
+#define DEFAULT_INTERVAL 5000
+static unsigned long gil_interval = DEFAULT_INTERVAL;
+#define INTERVAL (gil_interval >= 1 ? gil_interval : 1)
+
+/* Enable if you want to force the switching of threads at least every `gil_interval` */
+#undef FORCE_SWITCHING
+#define FORCE_SWITCHING
+
+
+/*
+ Notes about the implementation:
+
+ - The GIL is just a boolean variable (gil_locked) whose access is protected
+ by a mutex (gil_mutex), and whose changes are signalled by a condition
+ variable (gil_cond). gil_mutex is taken for short periods of time,
+ and therefore mostly uncontended.
+
+ - In the GIL-holding thread, the main loop (PyEval_EvalFrameEx) must be
+ able to release the GIL on demand by another thread. A volatile boolean
+ variable (gil_drop_request) is used for that purpose, which is checked
+ at every turn of the eval loop. That variable is set after a wait of
+ `interval` microseconds on `gil_cond` has timed out.
+
+ [Actually, another volatile boolean variable (eval_breaker) is used
+ which ORs several conditions into one. Volatile booleans are
+ sufficient as inter-thread signalling means since Python is run
+ on cache-coherent architectures only.]
+
+ - A thread wanting to take the GIL will first let pass a given amount of
+ time (`interval` microseconds) before setting gil_drop_request. This
+ encourages a defined switching period, but doesn't enforce it since
+ opcodes can take an arbitrary time to execute.
+
+ The `interval` value is available for the user to read and modify
+ using the Python API `sys.{get,set}switchinterval()`.
+
+ - When a thread releases the GIL and gil_drop_request is set, that thread
+ ensures that another GIL-awaiting thread gets scheduled.
+ It does so by waiting on a condition variable (switch_cond) until
+ the value of gil_last_holder is changed to something else than its
+ own thread state pointer, indicating that another thread was able to
+ take the GIL.
+
+ This is meant to prohibit the latency-adverse behaviour on multi-core
+ machines where one thread would speculatively release the GIL, but still
+ run and end up being the first to re-acquire it, making the "timeslices"
+ much longer than expected.
+ (Note: this mechanism is enabled with FORCE_SWITCHING above)
+*/
+
+#ifndef _POSIX_THREADS
+/* This means pthreads are not implemented in libc headers, hence the macro
+ not present in unistd.h. But they still can be implemented as an external
+ library (e.g. gnu pth in pthread emulation) */
+# ifdef HAVE_PTHREAD_H
+# include <pthread.h> /* _POSIX_THREADS */
+# endif
+#endif
+
+
+#ifdef _POSIX_THREADS
+
+/*
+ * POSIX support
+ */
+
+#include <pthread.h>
+
+#define ADD_MICROSECONDS(tv, interval) \
+do { \
+ tv.tv_usec += (long) interval; \
+ tv.tv_sec += tv.tv_usec / 1000000; \
+ tv.tv_usec %= 1000000; \
+} while (0)
+
+/* We assume all modern POSIX systems have gettimeofday() */
+#ifdef GETTIMEOFDAY_NO_TZ
+#define GETTIMEOFDAY(ptv) gettimeofday(ptv)
+#else
+#define GETTIMEOFDAY(ptv) gettimeofday(ptv, (struct timezone *)NULL)
+#endif
+
+#define MUTEX_T pthread_mutex_t
+#define MUTEX_INIT(mut) \
+ if (pthread_mutex_init(&mut, NULL)) { \
+ Py_FatalError("pthread_mutex_init(" #mut ") failed"); };
+#define MUTEX_LOCK(mut) \
+ if (pthread_mutex_lock(&mut)) { \
+ Py_FatalError("pthread_mutex_lock(" #mut ") failed"); };
+#define MUTEX_UNLOCK(mut) \
+ if (pthread_mutex_unlock(&mut)) { \
+ Py_FatalError("pthread_mutex_unlock(" #mut ") failed"); };
+
+#define COND_T pthread_cond_t
+#define COND_INIT(cond) \
+ if (pthread_cond_init(&cond, NULL)) { \
+ Py_FatalError("pthread_cond_init(" #cond ") failed"); };
+#define COND_PREPARE(cond)
+#define COND_SIGNAL(cond) \
+ if (pthread_cond_signal(&cond)) { \
+ Py_FatalError("pthread_cond_signal(" #cond ") failed"); };
+#define COND_WAIT(cond, mut) \
+ if (pthread_cond_wait(&cond, &mut)) { \
+ Py_FatalError("pthread_cond_wait(" #cond ") failed"); };
+#define COND_TIMED_WAIT(cond, mut, microseconds, timeout_result) \
+ { \
+ int r; \
+ struct timespec ts; \
+ struct timeval deadline; \
+ \
+ GETTIMEOFDAY(&deadline); \
+ ADD_MICROSECONDS(deadline, microseconds); \
+ ts.tv_sec = deadline.tv_sec; \
+ ts.tv_nsec = deadline.tv_usec * 1000; \
+ \
+ r = pthread_cond_timedwait(&cond, &mut, &ts); \
+ if (r == ETIMEDOUT) \
+ timeout_result = 1; \
+ else if (r) \
+ Py_FatalError("pthread_cond_timedwait(" #cond ") failed"); \
+ else \
+ timeout_result = 0; \
+ } \
+
+#elif defined(NT_THREADS)
+
+/*
+ * Windows (2000 and later, as well as (hopefully) CE) support
+ */
+
+#include <windows.h>
+
+#define MUTEX_T HANDLE
+#define MUTEX_INIT(mut) \
+ if (!(mut = CreateMutex(NULL, FALSE, NULL))) { \
+ Py_FatalError("CreateMutex(" #mut ") failed"); };
+#define MUTEX_LOCK(mut) \
+ if (WaitForSingleObject(mut, INFINITE) != WAIT_OBJECT_0) { \
+ Py_FatalError("WaitForSingleObject(" #mut ") failed"); };
+#define MUTEX_UNLOCK(mut) \
+ if (!ReleaseMutex(mut)) { \
+ Py_FatalError("ReleaseMutex(" #mut ") failed"); };
+
+/* We emulate condition variables with events. It is sufficient here.
+ (WaitForMultipleObjects() allows the event to be caught and the mutex
+ to be taken atomically) */
+#define COND_T HANDLE
+#define COND_INIT(cond) \
+ /* auto-reset, non-signalled */ \
+ if (!(cond = CreateEvent(NULL, FALSE, FALSE, NULL))) { \
+ Py_FatalError("CreateMutex(" #cond ") failed"); };
+#define COND_PREPARE(cond) \
+ if (!ResetEvent(cond)) { \
+ Py_FatalError("ResetEvent(" #cond ") failed"); };
+#define COND_SIGNAL(cond) \
+ if (!SetEvent(cond)) { \
+ Py_FatalError("SetEvent(" #cond ") failed"); };
+#define COND_WAIT(cond, mut) \
+ { \
+ DWORD r; \
+ HANDLE objects[2] = { cond, mut }; \
+ MUTEX_UNLOCK(mut); \
+ r = WaitForMultipleObjects(2, objects, TRUE, INFINITE); \
+ if (r != WAIT_OBJECT_0) \
+ Py_FatalError("WaitForSingleObject(" #cond ") failed"); \
+ }
+#define COND_TIMED_WAIT(cond, mut, microseconds, timeout_result) \
+ { \
+ DWORD r; \
+ HANDLE objects[2] = { cond, mut }; \
+ MUTEX_UNLOCK(mut); \
+ r = WaitForMultipleObjects(2, objects, TRUE, microseconds / 1000); \
+ if (r == WAIT_TIMEOUT) { \
+ MUTEX_LOCK(mut); \
+ timeout_result = 1; \
+ } \
+ else if (r != WAIT_OBJECT_0) \
+ Py_FatalError("WaitForSingleObject(" #cond ") failed"); \
+ else \
+ timeout_result = 0; \
+ }
+
+#else
+
+#error You need either a POSIX-compatible or a Windows system!
+
+#endif /* _POSIX_THREADS, NT_THREADS */
+
+
+/* Whether the GIL is already taken (-1 if uninitialized). This is volatile
+ because it can be read without any lock taken in ceval.c. */
+static volatile int gil_locked = -1;
+/* Number of GIL switches since the beginning. */
+static unsigned long gil_switch_number = 0;
+/* Last thread holding / having held the GIL. This helps us know whether
+ anyone else was scheduled after we dropped the GIL. */
+static PyThreadState *gil_last_holder = NULL;
+
+/* This condition variable allows one or several threads to wait until
+ the GIL is released. In addition, the mutex also protects the above
+ variables. */
+static COND_T gil_cond;
+static MUTEX_T gil_mutex;
+
+#ifdef FORCE_SWITCHING
+/* This condition variable helps the GIL-releasing thread wait for
+ a GIL-awaiting thread to be scheduled and take the GIL. */
+static COND_T switch_cond;
+static MUTEX_T switch_mutex;
+#endif
+
+
+static int gil_created(void)
+{
+ return gil_locked >= 0;
+}
+
+static void create_gil(void)
+{
+ MUTEX_INIT(gil_mutex);
+#ifdef FORCE_SWITCHING
+ MUTEX_INIT(switch_mutex);
+#endif
+ COND_INIT(gil_cond);
+#ifdef FORCE_SWITCHING
+ COND_INIT(switch_cond);
+#endif
+ gil_locked = 0;
+ gil_last_holder = NULL;
+}
+
+static void recreate_gil(void)
+{
+ create_gil();
+}
+
+static void drop_gil(PyThreadState *tstate)
+{
+ /* NOTE: tstate is allowed to be NULL. */
+ if (!gil_locked)
+ Py_FatalError("drop_gil: GIL is not locked");
+ if (tstate != NULL && tstate != gil_last_holder)
+ Py_FatalError("drop_gil: wrong thread state");
+
+ MUTEX_LOCK(gil_mutex);
+ gil_locked = 0;
+ COND_SIGNAL(gil_cond);
+#ifdef FORCE_SWITCHING
+ COND_PREPARE(switch_cond);
+#endif
+ MUTEX_UNLOCK(gil_mutex);
+
+#ifdef FORCE_SWITCHING
+ if (gil_drop_request) {
+ MUTEX_LOCK(switch_mutex);
+ /* Not switched yet => wait */
+ if (gil_last_holder == tstate)
+ COND_WAIT(switch_cond, switch_mutex);
+ MUTEX_UNLOCK(switch_mutex);
+ }
+#endif
+}
+
+static void take_gil(PyThreadState *tstate)
+{
+ int err;
+ if (tstate == NULL)
+ Py_FatalError("take_gil: NULL tstate");
+
+ err = errno;
+ MUTEX_LOCK(gil_mutex);
+
+ if (!gil_locked)
+ goto _ready;
+
+ COND_PREPARE(gil_cond);
+ while (gil_locked) {
+ int timed_out = 0;
+ unsigned long saved_switchnum;
+
+ saved_switchnum = gil_switch_number;
+ COND_TIMED_WAIT(gil_cond, gil_mutex, INTERVAL, timed_out);
+ /* If we timed out and no switch occurred in the meantime, it is time
+ to ask the GIL-holding thread to drop it. */
+ if (timed_out && gil_locked && gil_switch_number == saved_switchnum) {
+ SET_GIL_DROP_REQUEST();
+ }
+ }
+_ready:
+#ifdef FORCE_SWITCHING
+ /* This mutex must be taken before modifying gil_last_holder (see drop_gil()). */
+ MUTEX_LOCK(switch_mutex);
+#endif
+ /* We now hold the GIL */
+ gil_locked = 1;
+
+ if (tstate != gil_last_holder) {
+ gil_last_holder = tstate;
+ ++gil_switch_number;
+ }
+#ifdef FORCE_SWITCHING
+ COND_SIGNAL(switch_cond);
+ MUTEX_UNLOCK(switch_mutex);
+#endif
+ if (gil_drop_request) {
+ RESET_GIL_DROP_REQUEST();
+ }
+ if (tstate->async_exc != NULL) {
+ _PyEval_SignalAsyncExc();
+ }
+
+ MUTEX_UNLOCK(gil_mutex);
+ errno = err;
+}
+
+void _PyEval_SetSwitchInterval(unsigned long microseconds)
+{
+ gil_interval = microseconds;
+}
+
+unsigned long _PyEval_GetSwitchInterval()
+{
+ return gil_interval;
+}