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https://github.com/python/cpython
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![Mark Shannon](/assets/img/avatar_default.png)
* Check eval-breaker in ENTER_EXECUTOR. * Make sure that frame->prev_instr is set before entering executor.
1184 lines
37 KiB
C
1184 lines
37 KiB
C
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#include "Python.h"
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#include "pycore_atomic.h" // _Py_atomic_int
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#include "pycore_ceval.h" // _PyEval_SignalReceived()
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#include "pycore_pyerrors.h" // _PyErr_GetRaisedException()
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#include "pycore_pylifecycle.h" // _PyErr_Print()
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#include "pycore_initconfig.h" // _PyStatus_OK()
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#include "pycore_interp.h" // _Py_RunGC()
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#include "pycore_pymem.h" // _PyMem_IsPtrFreed()
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/*
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Notes about the implementation:
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- The GIL is just a boolean variable (locked) whose access is protected
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by a mutex (gil_mutex), and whose changes are signalled by a condition
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variable (gil_cond). gil_mutex is taken for short periods of time,
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and therefore mostly uncontended.
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- In the GIL-holding thread, the main loop (PyEval_EvalFrameEx) must be
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able to release the GIL on demand by another thread. A volatile boolean
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variable (gil_drop_request) is used for that purpose, which is checked
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at every turn of the eval loop. That variable is set after a wait of
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`interval` microseconds on `gil_cond` has timed out.
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[Actually, another volatile boolean variable (eval_breaker) is used
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which ORs several conditions into one. Volatile booleans are
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sufficient as inter-thread signalling means since Python is run
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on cache-coherent architectures only.]
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- A thread wanting to take the GIL will first let pass a given amount of
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time (`interval` microseconds) before setting gil_drop_request. This
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encourages a defined switching period, but doesn't enforce it since
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opcodes can take an arbitrary time to execute.
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The `interval` value is available for the user to read and modify
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using the Python API `sys.{get,set}switchinterval()`.
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- When a thread releases the GIL and gil_drop_request is set, that thread
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ensures that another GIL-awaiting thread gets scheduled.
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It does so by waiting on a condition variable (switch_cond) until
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the value of last_holder is changed to something else than its
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own thread state pointer, indicating that another thread was able to
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take the GIL.
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This is meant to prohibit the latency-adverse behaviour on multi-core
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machines where one thread would speculatively release the GIL, but still
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run and end up being the first to re-acquire it, making the "timeslices"
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much longer than expected.
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(Note: this mechanism is enabled with FORCE_SWITCHING above)
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*/
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// GH-89279: Force inlining by using a macro.
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#if defined(_MSC_VER) && SIZEOF_INT == 4
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#define _Py_atomic_load_relaxed_int32(ATOMIC_VAL) (assert(sizeof((ATOMIC_VAL)->_value) == 4), *((volatile int*)&((ATOMIC_VAL)->_value)))
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#else
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#define _Py_atomic_load_relaxed_int32(ATOMIC_VAL) _Py_atomic_load_relaxed(ATOMIC_VAL)
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#endif
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/* This can set eval_breaker to 0 even though gil_drop_request became
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1. We believe this is all right because the eval loop will release
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the GIL eventually anyway. */
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static inline void
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COMPUTE_EVAL_BREAKER(PyInterpreterState *interp,
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struct _ceval_runtime_state *ceval,
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struct _ceval_state *ceval2)
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{
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_Py_atomic_store_relaxed(&ceval2->eval_breaker,
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_Py_atomic_load_relaxed_int32(&ceval2->gil_drop_request)
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| (_Py_atomic_load_relaxed_int32(&ceval->signals_pending)
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&& _Py_ThreadCanHandleSignals(interp))
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| (_Py_atomic_load_relaxed_int32(&ceval2->pending.calls_to_do))
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| (_Py_IsMainThread() && _Py_IsMainInterpreter(interp)
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&&_Py_atomic_load_relaxed_int32(&ceval->pending_mainthread.calls_to_do))
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| ceval2->pending.async_exc
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| _Py_atomic_load_relaxed_int32(&ceval2->gc_scheduled));
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}
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static inline void
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SET_GIL_DROP_REQUEST(PyInterpreterState *interp)
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{
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struct _ceval_state *ceval2 = &interp->ceval;
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_Py_atomic_store_relaxed(&ceval2->gil_drop_request, 1);
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_Py_atomic_store_relaxed(&ceval2->eval_breaker, 1);
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}
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static inline void
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RESET_GIL_DROP_REQUEST(PyInterpreterState *interp)
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{
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struct _ceval_runtime_state *ceval = &interp->runtime->ceval;
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struct _ceval_state *ceval2 = &interp->ceval;
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_Py_atomic_store_relaxed(&ceval2->gil_drop_request, 0);
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COMPUTE_EVAL_BREAKER(interp, ceval, ceval2);
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}
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static inline void
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SIGNAL_PENDING_CALLS(struct _pending_calls *pending, PyInterpreterState *interp)
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{
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struct _ceval_runtime_state *ceval = &interp->runtime->ceval;
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struct _ceval_state *ceval2 = &interp->ceval;
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_Py_atomic_store_relaxed(&pending->calls_to_do, 1);
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COMPUTE_EVAL_BREAKER(interp, ceval, ceval2);
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}
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static inline void
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UNSIGNAL_PENDING_CALLS(PyInterpreterState *interp)
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{
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struct _ceval_runtime_state *ceval = &interp->runtime->ceval;
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struct _ceval_state *ceval2 = &interp->ceval;
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if (_Py_IsMainThread() && _Py_IsMainInterpreter(interp)) {
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_Py_atomic_store_relaxed(&ceval->pending_mainthread.calls_to_do, 0);
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}
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_Py_atomic_store_relaxed(&ceval2->pending.calls_to_do, 0);
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COMPUTE_EVAL_BREAKER(interp, ceval, ceval2);
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}
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static inline void
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SIGNAL_PENDING_SIGNALS(PyInterpreterState *interp, int force)
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{
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struct _ceval_runtime_state *ceval = &interp->runtime->ceval;
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struct _ceval_state *ceval2 = &interp->ceval;
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_Py_atomic_store_relaxed(&ceval->signals_pending, 1);
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if (force) {
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_Py_atomic_store_relaxed(&ceval2->eval_breaker, 1);
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}
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else {
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/* eval_breaker is not set to 1 if thread_can_handle_signals() is false */
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COMPUTE_EVAL_BREAKER(interp, ceval, ceval2);
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}
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}
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static inline void
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UNSIGNAL_PENDING_SIGNALS(PyInterpreterState *interp)
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{
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struct _ceval_runtime_state *ceval = &interp->runtime->ceval;
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struct _ceval_state *ceval2 = &interp->ceval;
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_Py_atomic_store_relaxed(&ceval->signals_pending, 0);
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COMPUTE_EVAL_BREAKER(interp, ceval, ceval2);
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}
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static inline void
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SIGNAL_ASYNC_EXC(PyInterpreterState *interp)
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{
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struct _ceval_state *ceval2 = &interp->ceval;
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ceval2->pending.async_exc = 1;
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_Py_atomic_store_relaxed(&ceval2->eval_breaker, 1);
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}
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static inline void
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UNSIGNAL_ASYNC_EXC(PyInterpreterState *interp)
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{
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struct _ceval_runtime_state *ceval = &interp->runtime->ceval;
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struct _ceval_state *ceval2 = &interp->ceval;
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ceval2->pending.async_exc = 0;
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COMPUTE_EVAL_BREAKER(interp, ceval, ceval2);
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}
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#ifndef NDEBUG
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/* Ensure that tstate is valid */
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static int
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is_tstate_valid(PyThreadState *tstate)
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{
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assert(!_PyMem_IsPtrFreed(tstate));
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assert(!_PyMem_IsPtrFreed(tstate->interp));
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return 1;
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}
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#endif
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/*
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* Implementation of the Global Interpreter Lock (GIL).
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*/
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#include <stdlib.h>
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#include <errno.h>
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#include "pycore_atomic.h"
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#include "condvar.h"
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#define MUTEX_INIT(mut) \
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if (PyMUTEX_INIT(&(mut))) { \
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Py_FatalError("PyMUTEX_INIT(" #mut ") failed"); };
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#define MUTEX_FINI(mut) \
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if (PyMUTEX_FINI(&(mut))) { \
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Py_FatalError("PyMUTEX_FINI(" #mut ") failed"); };
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#define MUTEX_LOCK(mut) \
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if (PyMUTEX_LOCK(&(mut))) { \
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Py_FatalError("PyMUTEX_LOCK(" #mut ") failed"); };
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#define MUTEX_UNLOCK(mut) \
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if (PyMUTEX_UNLOCK(&(mut))) { \
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Py_FatalError("PyMUTEX_UNLOCK(" #mut ") failed"); };
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#define COND_INIT(cond) \
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if (PyCOND_INIT(&(cond))) { \
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Py_FatalError("PyCOND_INIT(" #cond ") failed"); };
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#define COND_FINI(cond) \
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if (PyCOND_FINI(&(cond))) { \
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Py_FatalError("PyCOND_FINI(" #cond ") failed"); };
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#define COND_SIGNAL(cond) \
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if (PyCOND_SIGNAL(&(cond))) { \
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Py_FatalError("PyCOND_SIGNAL(" #cond ") failed"); };
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#define COND_WAIT(cond, mut) \
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if (PyCOND_WAIT(&(cond), &(mut))) { \
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Py_FatalError("PyCOND_WAIT(" #cond ") failed"); };
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#define COND_TIMED_WAIT(cond, mut, microseconds, timeout_result) \
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{ \
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int r = PyCOND_TIMEDWAIT(&(cond), &(mut), (microseconds)); \
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if (r < 0) \
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Py_FatalError("PyCOND_WAIT(" #cond ") failed"); \
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if (r) /* 1 == timeout, 2 == impl. can't say, so assume timeout */ \
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timeout_result = 1; \
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else \
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timeout_result = 0; \
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} \
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#define DEFAULT_INTERVAL 5000
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static void _gil_initialize(struct _gil_runtime_state *gil)
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{
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_Py_atomic_int uninitialized = {-1};
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gil->locked = uninitialized;
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gil->interval = DEFAULT_INTERVAL;
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}
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static int gil_created(struct _gil_runtime_state *gil)
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{
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if (gil == NULL) {
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return 0;
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}
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return (_Py_atomic_load_explicit(&gil->locked, _Py_memory_order_acquire) >= 0);
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}
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static void create_gil(struct _gil_runtime_state *gil)
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{
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MUTEX_INIT(gil->mutex);
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#ifdef FORCE_SWITCHING
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MUTEX_INIT(gil->switch_mutex);
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#endif
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COND_INIT(gil->cond);
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#ifdef FORCE_SWITCHING
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COND_INIT(gil->switch_cond);
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#endif
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_Py_atomic_store_relaxed(&gil->last_holder, 0);
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_Py_ANNOTATE_RWLOCK_CREATE(&gil->locked);
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_Py_atomic_store_explicit(&gil->locked, 0, _Py_memory_order_release);
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}
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static void destroy_gil(struct _gil_runtime_state *gil)
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{
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/* some pthread-like implementations tie the mutex to the cond
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* and must have the cond destroyed first.
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*/
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COND_FINI(gil->cond);
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MUTEX_FINI(gil->mutex);
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#ifdef FORCE_SWITCHING
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COND_FINI(gil->switch_cond);
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MUTEX_FINI(gil->switch_mutex);
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#endif
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_Py_atomic_store_explicit(&gil->locked, -1,
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_Py_memory_order_release);
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_Py_ANNOTATE_RWLOCK_DESTROY(&gil->locked);
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}
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#ifdef HAVE_FORK
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static void recreate_gil(struct _gil_runtime_state *gil)
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{
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_Py_ANNOTATE_RWLOCK_DESTROY(&gil->locked);
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/* XXX should we destroy the old OS resources here? */
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create_gil(gil);
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}
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#endif
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static void
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drop_gil(struct _ceval_state *ceval, PyThreadState *tstate)
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{
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/* If tstate is NULL, the caller is indicating that we're releasing
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the GIL for the last time in this thread. This is particularly
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relevant when the current thread state is finalizing or its
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interpreter is finalizing (either may be in an inconsistent
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state). In that case the current thread will definitely
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never try to acquire the GIL again. */
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// XXX It may be more correct to check tstate->_status.finalizing.
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// XXX assert(tstate == NULL || !tstate->_status.cleared);
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struct _gil_runtime_state *gil = ceval->gil;
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if (!_Py_atomic_load_relaxed(&gil->locked)) {
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Py_FatalError("drop_gil: GIL is not locked");
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}
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/* tstate is allowed to be NULL (early interpreter init) */
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if (tstate != NULL) {
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/* Sub-interpreter support: threads might have been switched
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under our feet using PyThreadState_Swap(). Fix the GIL last
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holder variable so that our heuristics work. */
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_Py_atomic_store_relaxed(&gil->last_holder, (uintptr_t)tstate);
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}
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MUTEX_LOCK(gil->mutex);
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_Py_ANNOTATE_RWLOCK_RELEASED(&gil->locked, /*is_write=*/1);
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_Py_atomic_store_relaxed(&gil->locked, 0);
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COND_SIGNAL(gil->cond);
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MUTEX_UNLOCK(gil->mutex);
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#ifdef FORCE_SWITCHING
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/* We check tstate first in case we might be releasing the GIL for
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the last time in this thread. In that case there's a possible
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race with tstate->interp getting deleted after gil->mutex is
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unlocked and before the following code runs, leading to a crash.
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We can use (tstate == NULL) to indicate the thread is done with
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the GIL, and that's the only time we might delete the
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interpreter, so checking tstate first prevents the crash.
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See https://github.com/python/cpython/issues/104341. */
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if (tstate != NULL && _Py_atomic_load_relaxed(&ceval->gil_drop_request)) {
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MUTEX_LOCK(gil->switch_mutex);
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/* Not switched yet => wait */
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if (((PyThreadState*)_Py_atomic_load_relaxed(&gil->last_holder)) == tstate)
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{
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assert(is_tstate_valid(tstate));
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RESET_GIL_DROP_REQUEST(tstate->interp);
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/* NOTE: if COND_WAIT does not atomically start waiting when
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releasing the mutex, another thread can run through, take
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the GIL and drop it again, and reset the condition
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before we even had a chance to wait for it. */
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COND_WAIT(gil->switch_cond, gil->switch_mutex);
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}
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MUTEX_UNLOCK(gil->switch_mutex);
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}
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#endif
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}
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/* Check if a Python thread must exit immediately, rather than taking the GIL
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if Py_Finalize() has been called.
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When this function is called by a daemon thread after Py_Finalize() has been
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called, the GIL does no longer exist.
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tstate must be non-NULL. */
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static inline int
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tstate_must_exit(PyThreadState *tstate)
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{
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/* bpo-39877: Access _PyRuntime directly rather than using
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tstate->interp->runtime to support calls from Python daemon threads.
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After Py_Finalize() has been called, tstate can be a dangling pointer:
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point to PyThreadState freed memory. */
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PyThreadState *finalizing = _PyRuntimeState_GetFinalizing(&_PyRuntime);
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if (finalizing == NULL) {
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finalizing = _PyInterpreterState_GetFinalizing(tstate->interp);
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}
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return (finalizing != NULL && finalizing != tstate);
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}
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|
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/* Take the GIL.
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The function saves errno at entry and restores its value at exit.
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tstate must be non-NULL. */
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static void
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take_gil(PyThreadState *tstate)
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{
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int err = errno;
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assert(tstate != NULL);
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/* We shouldn't be using a thread state that isn't viable any more. */
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// XXX It may be more correct to check tstate->_status.finalizing.
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// XXX assert(!tstate->_status.cleared);
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if (tstate_must_exit(tstate)) {
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/* bpo-39877: If Py_Finalize() has been called and tstate is not the
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thread which called Py_Finalize(), exit immediately the thread.
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This code path can be reached by a daemon thread after Py_Finalize()
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completes. In this case, tstate is a dangling pointer: points to
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PyThreadState freed memory. */
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PyThread_exit_thread();
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}
|
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assert(is_tstate_valid(tstate));
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PyInterpreterState *interp = tstate->interp;
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struct _ceval_state *ceval = &interp->ceval;
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struct _gil_runtime_state *gil = ceval->gil;
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/* Check that _PyEval_InitThreads() was called to create the lock */
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assert(gil_created(gil));
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MUTEX_LOCK(gil->mutex);
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if (!_Py_atomic_load_relaxed(&gil->locked)) {
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goto _ready;
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}
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int drop_requested = 0;
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while (_Py_atomic_load_relaxed(&gil->locked)) {
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unsigned long saved_switchnum = gil->switch_number;
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unsigned long interval = (gil->interval >= 1 ? gil->interval : 1);
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int timed_out = 0;
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COND_TIMED_WAIT(gil->cond, gil->mutex, interval, timed_out);
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/* If we timed out and no switch occurred in the meantime, it is time
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to ask the GIL-holding thread to drop it. */
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if (timed_out &&
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_Py_atomic_load_relaxed(&gil->locked) &&
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gil->switch_number == saved_switchnum)
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{
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if (tstate_must_exit(tstate)) {
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MUTEX_UNLOCK(gil->mutex);
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// gh-96387: If the loop requested a drop request in a previous
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// iteration, reset the request. Otherwise, drop_gil() can
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// block forever waiting for the thread which exited. Drop
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// requests made by other threads are also reset: these threads
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// may have to request again a drop request (iterate one more
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// time).
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if (drop_requested) {
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RESET_GIL_DROP_REQUEST(interp);
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}
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PyThread_exit_thread();
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}
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assert(is_tstate_valid(tstate));
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SET_GIL_DROP_REQUEST(interp);
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drop_requested = 1;
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}
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}
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_ready:
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#ifdef FORCE_SWITCHING
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/* This mutex must be taken before modifying gil->last_holder:
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see drop_gil(). */
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MUTEX_LOCK(gil->switch_mutex);
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#endif
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/* We now hold the GIL */
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_Py_atomic_store_relaxed(&gil->locked, 1);
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_Py_ANNOTATE_RWLOCK_ACQUIRED(&gil->locked, /*is_write=*/1);
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|
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if (tstate != (PyThreadState*)_Py_atomic_load_relaxed(&gil->last_holder)) {
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_Py_atomic_store_relaxed(&gil->last_holder, (uintptr_t)tstate);
|
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++gil->switch_number;
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}
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#ifdef FORCE_SWITCHING
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COND_SIGNAL(gil->switch_cond);
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MUTEX_UNLOCK(gil->switch_mutex);
|
|
#endif
|
|
|
|
if (tstate_must_exit(tstate)) {
|
|
/* bpo-36475: If Py_Finalize() has been called and tstate is not
|
|
the thread which called Py_Finalize(), exit immediately the
|
|
thread.
|
|
|
|
This code path can be reached by a daemon thread which was waiting
|
|
in take_gil() while the main thread called
|
|
wait_for_thread_shutdown() from Py_Finalize(). */
|
|
MUTEX_UNLOCK(gil->mutex);
|
|
drop_gil(ceval, tstate);
|
|
PyThread_exit_thread();
|
|
}
|
|
assert(is_tstate_valid(tstate));
|
|
|
|
if (_Py_atomic_load_relaxed(&ceval->gil_drop_request)) {
|
|
RESET_GIL_DROP_REQUEST(interp);
|
|
}
|
|
else {
|
|
/* bpo-40010: eval_breaker should be recomputed to be set to 1 if there
|
|
is a pending signal: signal received by another thread which cannot
|
|
handle signals.
|
|
|
|
Note: RESET_GIL_DROP_REQUEST() calls COMPUTE_EVAL_BREAKER(). */
|
|
COMPUTE_EVAL_BREAKER(interp, &_PyRuntime.ceval, ceval);
|
|
}
|
|
|
|
/* Don't access tstate if the thread must exit */
|
|
if (tstate->async_exc != NULL) {
|
|
_PyEval_SignalAsyncExc(tstate->interp);
|
|
}
|
|
|
|
MUTEX_UNLOCK(gil->mutex);
|
|
|
|
errno = err;
|
|
}
|
|
|
|
void _PyEval_SetSwitchInterval(unsigned long microseconds)
|
|
{
|
|
PyInterpreterState *interp = _PyInterpreterState_GET();
|
|
struct _gil_runtime_state *gil = interp->ceval.gil;
|
|
assert(gil != NULL);
|
|
gil->interval = microseconds;
|
|
}
|
|
|
|
unsigned long _PyEval_GetSwitchInterval(void)
|
|
{
|
|
PyInterpreterState *interp = _PyInterpreterState_GET();
|
|
struct _gil_runtime_state *gil = interp->ceval.gil;
|
|
assert(gil != NULL);
|
|
return gil->interval;
|
|
}
|
|
|
|
|
|
int
|
|
_PyEval_ThreadsInitialized(void)
|
|
{
|
|
/* XXX This is only needed for an assert in PyGILState_Ensure(),
|
|
* which currently does not work with subinterpreters.
|
|
* Thus we only use the main interpreter. */
|
|
PyInterpreterState *interp = _PyInterpreterState_Main();
|
|
if (interp == NULL) {
|
|
return 0;
|
|
}
|
|
struct _gil_runtime_state *gil = interp->ceval.gil;
|
|
return gil_created(gil);
|
|
}
|
|
|
|
// Function removed in the Python 3.13 API but kept in the stable ABI.
|
|
PyAPI_FUNC(int)
|
|
PyEval_ThreadsInitialized(void)
|
|
{
|
|
return _PyEval_ThreadsInitialized();
|
|
}
|
|
|
|
static inline int
|
|
current_thread_holds_gil(struct _gil_runtime_state *gil, PyThreadState *tstate)
|
|
{
|
|
if (((PyThreadState*)_Py_atomic_load_relaxed(&gil->last_holder)) != tstate) {
|
|
return 0;
|
|
}
|
|
return _Py_atomic_load_relaxed(&gil->locked);
|
|
}
|
|
|
|
static void
|
|
init_shared_gil(PyInterpreterState *interp, struct _gil_runtime_state *gil)
|
|
{
|
|
assert(gil_created(gil));
|
|
interp->ceval.gil = gil;
|
|
interp->ceval.own_gil = 0;
|
|
}
|
|
|
|
static void
|
|
init_own_gil(PyInterpreterState *interp, struct _gil_runtime_state *gil)
|
|
{
|
|
assert(!gil_created(gil));
|
|
create_gil(gil);
|
|
assert(gil_created(gil));
|
|
interp->ceval.gil = gil;
|
|
interp->ceval.own_gil = 1;
|
|
}
|
|
|
|
PyStatus
|
|
_PyEval_InitGIL(PyThreadState *tstate, int own_gil)
|
|
{
|
|
assert(tstate->interp->ceval.gil == NULL);
|
|
int locked;
|
|
if (!own_gil) {
|
|
/* The interpreter will share the main interpreter's instead. */
|
|
PyInterpreterState *main_interp = _PyInterpreterState_Main();
|
|
assert(tstate->interp != main_interp);
|
|
struct _gil_runtime_state *gil = main_interp->ceval.gil;
|
|
init_shared_gil(tstate->interp, gil);
|
|
locked = current_thread_holds_gil(gil, tstate);
|
|
}
|
|
else {
|
|
PyThread_init_thread();
|
|
init_own_gil(tstate->interp, &tstate->interp->_gil);
|
|
locked = 0;
|
|
}
|
|
if (!locked) {
|
|
take_gil(tstate);
|
|
}
|
|
|
|
return _PyStatus_OK();
|
|
}
|
|
|
|
void
|
|
_PyEval_FiniGIL(PyInterpreterState *interp)
|
|
{
|
|
struct _gil_runtime_state *gil = interp->ceval.gil;
|
|
if (gil == NULL) {
|
|
/* It was already finalized (or hasn't been initialized yet). */
|
|
assert(!interp->ceval.own_gil);
|
|
return;
|
|
}
|
|
else if (!interp->ceval.own_gil) {
|
|
#ifdef Py_DEBUG
|
|
PyInterpreterState *main_interp = _PyInterpreterState_Main();
|
|
assert(main_interp != NULL && interp != main_interp);
|
|
assert(interp->ceval.gil == main_interp->ceval.gil);
|
|
#endif
|
|
interp->ceval.gil = NULL;
|
|
return;
|
|
}
|
|
|
|
if (!gil_created(gil)) {
|
|
/* First Py_InitializeFromConfig() call: the GIL doesn't exist
|
|
yet: do nothing. */
|
|
return;
|
|
}
|
|
|
|
destroy_gil(gil);
|
|
assert(!gil_created(gil));
|
|
interp->ceval.gil = NULL;
|
|
}
|
|
|
|
// Function removed in the Python 3.13 API but kept in the stable ABI.
|
|
PyAPI_FUNC(void)
|
|
PyEval_InitThreads(void)
|
|
{
|
|
/* Do nothing: kept for backward compatibility */
|
|
}
|
|
|
|
void
|
|
_PyEval_Fini(void)
|
|
{
|
|
#ifdef Py_STATS
|
|
_Py_PrintSpecializationStats(1);
|
|
#endif
|
|
}
|
|
|
|
// Function removed in the Python 3.13 API but kept in the stable ABI.
|
|
PyAPI_FUNC(void)
|
|
PyEval_AcquireLock(void)
|
|
{
|
|
PyThreadState *tstate = _PyThreadState_GET();
|
|
_Py_EnsureTstateNotNULL(tstate);
|
|
|
|
take_gil(tstate);
|
|
}
|
|
|
|
// Function removed in the Python 3.13 API but kept in the stable ABI.
|
|
PyAPI_FUNC(void)
|
|
PyEval_ReleaseLock(void)
|
|
{
|
|
PyThreadState *tstate = _PyThreadState_GET();
|
|
/* This function must succeed when the current thread state is NULL.
|
|
We therefore avoid PyThreadState_Get() which dumps a fatal error
|
|
in debug mode. */
|
|
struct _ceval_state *ceval = &tstate->interp->ceval;
|
|
drop_gil(ceval, tstate);
|
|
}
|
|
|
|
void
|
|
_PyEval_AcquireLock(PyThreadState *tstate)
|
|
{
|
|
_Py_EnsureTstateNotNULL(tstate);
|
|
take_gil(tstate);
|
|
}
|
|
|
|
void
|
|
_PyEval_ReleaseLock(PyInterpreterState *interp, PyThreadState *tstate)
|
|
{
|
|
/* If tstate is NULL then we do not expect the current thread
|
|
to acquire the GIL ever again. */
|
|
assert(tstate == NULL || tstate->interp == interp);
|
|
struct _ceval_state *ceval = &interp->ceval;
|
|
drop_gil(ceval, tstate);
|
|
}
|
|
|
|
void
|
|
PyEval_AcquireThread(PyThreadState *tstate)
|
|
{
|
|
_Py_EnsureTstateNotNULL(tstate);
|
|
|
|
take_gil(tstate);
|
|
|
|
if (_PyThreadState_SwapNoGIL(tstate) != NULL) {
|
|
Py_FatalError("non-NULL old thread state");
|
|
}
|
|
}
|
|
|
|
void
|
|
PyEval_ReleaseThread(PyThreadState *tstate)
|
|
{
|
|
assert(is_tstate_valid(tstate));
|
|
|
|
PyThreadState *new_tstate = _PyThreadState_SwapNoGIL(NULL);
|
|
if (new_tstate != tstate) {
|
|
Py_FatalError("wrong thread state");
|
|
}
|
|
struct _ceval_state *ceval = &tstate->interp->ceval;
|
|
drop_gil(ceval, tstate);
|
|
}
|
|
|
|
#ifdef HAVE_FORK
|
|
/* This function is called from PyOS_AfterFork_Child to destroy all threads
|
|
which are not running in the child process, and clear internal locks
|
|
which might be held by those threads. */
|
|
PyStatus
|
|
_PyEval_ReInitThreads(PyThreadState *tstate)
|
|
{
|
|
assert(tstate->interp == _PyInterpreterState_Main());
|
|
|
|
struct _gil_runtime_state *gil = tstate->interp->ceval.gil;
|
|
if (!gil_created(gil)) {
|
|
return _PyStatus_OK();
|
|
}
|
|
recreate_gil(gil);
|
|
|
|
take_gil(tstate);
|
|
|
|
struct _pending_calls *pending = &tstate->interp->ceval.pending;
|
|
if (_PyThread_at_fork_reinit(&pending->lock) < 0) {
|
|
return _PyStatus_ERR("Can't reinitialize pending calls lock");
|
|
}
|
|
|
|
/* Destroy all threads except the current one */
|
|
_PyThreadState_DeleteExcept(tstate);
|
|
return _PyStatus_OK();
|
|
}
|
|
#endif
|
|
|
|
/* This function is used to signal that async exceptions are waiting to be
|
|
raised. */
|
|
|
|
void
|
|
_PyEval_SignalAsyncExc(PyInterpreterState *interp)
|
|
{
|
|
SIGNAL_ASYNC_EXC(interp);
|
|
}
|
|
|
|
PyThreadState *
|
|
PyEval_SaveThread(void)
|
|
{
|
|
PyThreadState *tstate = _PyThreadState_SwapNoGIL(NULL);
|
|
_Py_EnsureTstateNotNULL(tstate);
|
|
|
|
struct _ceval_state *ceval = &tstate->interp->ceval;
|
|
assert(gil_created(ceval->gil));
|
|
drop_gil(ceval, tstate);
|
|
return tstate;
|
|
}
|
|
|
|
void
|
|
PyEval_RestoreThread(PyThreadState *tstate)
|
|
{
|
|
_Py_EnsureTstateNotNULL(tstate);
|
|
|
|
take_gil(tstate);
|
|
|
|
_PyThreadState_SwapNoGIL(tstate);
|
|
}
|
|
|
|
|
|
/* Mechanism whereby asynchronously executing callbacks (e.g. UNIX
|
|
signal handlers or Mac I/O completion routines) can schedule calls
|
|
to a function to be called synchronously.
|
|
The synchronous function is called with one void* argument.
|
|
It should return 0 for success or -1 for failure -- failure should
|
|
be accompanied by an exception.
|
|
|
|
If registry succeeds, the registry function returns 0; if it fails
|
|
(e.g. due to too many pending calls) it returns -1 (without setting
|
|
an exception condition).
|
|
|
|
Note that because registry may occur from within signal handlers,
|
|
or other asynchronous events, calling malloc() is unsafe!
|
|
|
|
Any thread can schedule pending calls, but only the main thread
|
|
will execute them.
|
|
There is no facility to schedule calls to a particular thread, but
|
|
that should be easy to change, should that ever be required. In
|
|
that case, the static variables here should go into the python
|
|
threadstate.
|
|
*/
|
|
|
|
void
|
|
_PyEval_SignalReceived(PyInterpreterState *interp)
|
|
{
|
|
#ifdef MS_WINDOWS
|
|
// bpo-42296: On Windows, _PyEval_SignalReceived() is called from a signal
|
|
// handler which can run in a thread different than the Python thread, in
|
|
// which case _Py_ThreadCanHandleSignals() is wrong. Ignore
|
|
// _Py_ThreadCanHandleSignals() and always set eval_breaker to 1.
|
|
//
|
|
// The next eval_frame_handle_pending() call will call
|
|
// _Py_ThreadCanHandleSignals() to recompute eval_breaker.
|
|
int force = 1;
|
|
#else
|
|
int force = 0;
|
|
#endif
|
|
/* bpo-30703: Function called when the C signal handler of Python gets a
|
|
signal. We cannot queue a callback using _PyEval_AddPendingCall() since
|
|
that function is not async-signal-safe. */
|
|
SIGNAL_PENDING_SIGNALS(interp, force);
|
|
}
|
|
|
|
/* Push one item onto the queue while holding the lock. */
|
|
static int
|
|
_push_pending_call(struct _pending_calls *pending,
|
|
int (*func)(void *), void *arg)
|
|
{
|
|
int i = pending->last;
|
|
int j = (i + 1) % NPENDINGCALLS;
|
|
if (j == pending->first) {
|
|
return -1; /* Queue full */
|
|
}
|
|
pending->calls[i].func = func;
|
|
pending->calls[i].arg = arg;
|
|
pending->last = j;
|
|
return 0;
|
|
}
|
|
|
|
static int
|
|
_next_pending_call(struct _pending_calls *pending,
|
|
int (**func)(void *), void **arg)
|
|
{
|
|
int i = pending->first;
|
|
if (i == pending->last) {
|
|
/* Queue empty */
|
|
assert(pending->calls[i].func == NULL);
|
|
return -1;
|
|
}
|
|
*func = pending->calls[i].func;
|
|
*arg = pending->calls[i].arg;
|
|
return i;
|
|
}
|
|
|
|
/* Pop one item off the queue while holding the lock. */
|
|
static void
|
|
_pop_pending_call(struct _pending_calls *pending,
|
|
int (**func)(void *), void **arg)
|
|
{
|
|
int i = _next_pending_call(pending, func, arg);
|
|
if (i >= 0) {
|
|
pending->calls[i] = (struct _pending_call){0};
|
|
pending->first = (i + 1) % NPENDINGCALLS;
|
|
}
|
|
}
|
|
|
|
/* This implementation is thread-safe. It allows
|
|
scheduling to be made from any thread, and even from an executing
|
|
callback.
|
|
*/
|
|
|
|
int
|
|
_PyEval_AddPendingCall(PyInterpreterState *interp,
|
|
int (*func)(void *), void *arg,
|
|
int mainthreadonly)
|
|
{
|
|
assert(!mainthreadonly || _Py_IsMainInterpreter(interp));
|
|
struct _pending_calls *pending = &interp->ceval.pending;
|
|
if (mainthreadonly) {
|
|
/* The main thread only exists in the main interpreter. */
|
|
assert(_Py_IsMainInterpreter(interp));
|
|
pending = &_PyRuntime.ceval.pending_mainthread;
|
|
}
|
|
/* Ensure that _PyEval_InitState() was called
|
|
and that _PyEval_FiniState() is not called yet. */
|
|
assert(pending->lock != NULL);
|
|
|
|
PyThread_acquire_lock(pending->lock, WAIT_LOCK);
|
|
int result = _push_pending_call(pending, func, arg);
|
|
PyThread_release_lock(pending->lock);
|
|
|
|
/* signal main loop */
|
|
SIGNAL_PENDING_CALLS(pending, interp);
|
|
return result;
|
|
}
|
|
|
|
int
|
|
Py_AddPendingCall(int (*func)(void *), void *arg)
|
|
{
|
|
/* Legacy users of this API will continue to target the main thread
|
|
(of the main interpreter). */
|
|
PyInterpreterState *interp = _PyInterpreterState_Main();
|
|
return _PyEval_AddPendingCall(interp, func, arg, 1);
|
|
}
|
|
|
|
static int
|
|
handle_signals(PyThreadState *tstate)
|
|
{
|
|
assert(is_tstate_valid(tstate));
|
|
if (!_Py_ThreadCanHandleSignals(tstate->interp)) {
|
|
return 0;
|
|
}
|
|
|
|
UNSIGNAL_PENDING_SIGNALS(tstate->interp);
|
|
if (_PyErr_CheckSignalsTstate(tstate) < 0) {
|
|
/* On failure, re-schedule a call to handle_signals(). */
|
|
SIGNAL_PENDING_SIGNALS(tstate->interp, 0);
|
|
return -1;
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
static inline int
|
|
maybe_has_pending_calls(PyInterpreterState *interp)
|
|
{
|
|
struct _pending_calls *pending = &interp->ceval.pending;
|
|
if (_Py_atomic_load_relaxed_int32(&pending->calls_to_do)) {
|
|
return 1;
|
|
}
|
|
if (!_Py_IsMainThread() || !_Py_IsMainInterpreter(interp)) {
|
|
return 0;
|
|
}
|
|
pending = &_PyRuntime.ceval.pending_mainthread;
|
|
return _Py_atomic_load_relaxed_int32(&pending->calls_to_do);
|
|
}
|
|
|
|
static int
|
|
_make_pending_calls(struct _pending_calls *pending)
|
|
{
|
|
/* perform a bounded number of calls, in case of recursion */
|
|
for (int i=0; i<NPENDINGCALLS; i++) {
|
|
int (*func)(void *) = NULL;
|
|
void *arg = NULL;
|
|
|
|
/* pop one item off the queue while holding the lock */
|
|
PyThread_acquire_lock(pending->lock, WAIT_LOCK);
|
|
_pop_pending_call(pending, &func, &arg);
|
|
PyThread_release_lock(pending->lock);
|
|
|
|
/* having released the lock, perform the callback */
|
|
if (func == NULL) {
|
|
break;
|
|
}
|
|
if (func(arg) != 0) {
|
|
return -1;
|
|
}
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
static int
|
|
make_pending_calls(PyInterpreterState *interp)
|
|
{
|
|
struct _pending_calls *pending = &interp->ceval.pending;
|
|
struct _pending_calls *pending_main = &_PyRuntime.ceval.pending_mainthread;
|
|
|
|
/* Only one thread (per interpreter) may run the pending calls
|
|
at once. In the same way, we don't do recursive pending calls. */
|
|
PyThread_acquire_lock(pending->lock, WAIT_LOCK);
|
|
if (pending->busy) {
|
|
/* A pending call was added after another thread was already
|
|
handling the pending calls (and had already "unsignaled").
|
|
Once that thread is done, it may have taken care of all the
|
|
pending calls, or there might be some still waiting.
|
|
Regardless, this interpreter's pending calls will stay
|
|
"signaled" until that first thread has finished. At that
|
|
point the next thread to trip the eval breaker will take
|
|
care of any remaining pending calls. Until then, though,
|
|
all the interpreter's threads will be tripping the eval
|
|
breaker every time it's checked. */
|
|
PyThread_release_lock(pending->lock);
|
|
return 0;
|
|
}
|
|
pending->busy = 1;
|
|
PyThread_release_lock(pending->lock);
|
|
|
|
/* unsignal before starting to call callbacks, so that any callback
|
|
added in-between re-signals */
|
|
UNSIGNAL_PENDING_CALLS(interp);
|
|
|
|
if (_make_pending_calls(pending) != 0) {
|
|
pending->busy = 0;
|
|
/* There might not be more calls to make, but we play it safe. */
|
|
SIGNAL_PENDING_CALLS(pending, interp);
|
|
return -1;
|
|
}
|
|
|
|
if (_Py_IsMainThread() && _Py_IsMainInterpreter(interp)) {
|
|
if (_make_pending_calls(pending_main) != 0) {
|
|
pending->busy = 0;
|
|
/* There might not be more calls to make, but we play it safe. */
|
|
SIGNAL_PENDING_CALLS(pending_main, interp);
|
|
return -1;
|
|
}
|
|
}
|
|
|
|
pending->busy = 0;
|
|
return 0;
|
|
}
|
|
|
|
void
|
|
_Py_FinishPendingCalls(PyThreadState *tstate)
|
|
{
|
|
assert(PyGILState_Check());
|
|
assert(is_tstate_valid(tstate));
|
|
|
|
if (make_pending_calls(tstate->interp) < 0) {
|
|
PyObject *exc = _PyErr_GetRaisedException(tstate);
|
|
PyErr_BadInternalCall();
|
|
_PyErr_ChainExceptions1(exc);
|
|
_PyErr_Print(tstate);
|
|
}
|
|
}
|
|
|
|
int
|
|
_PyEval_MakePendingCalls(PyThreadState *tstate)
|
|
{
|
|
int res;
|
|
|
|
if (_Py_IsMainThread() && _Py_IsMainInterpreter(tstate->interp)) {
|
|
/* Python signal handler doesn't really queue a callback:
|
|
it only signals that a signal was received,
|
|
see _PyEval_SignalReceived(). */
|
|
res = handle_signals(tstate);
|
|
if (res != 0) {
|
|
return res;
|
|
}
|
|
}
|
|
|
|
res = make_pending_calls(tstate->interp);
|
|
if (res != 0) {
|
|
return res;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
/* Py_MakePendingCalls() is a simple wrapper for the sake
|
|
of backward-compatibility. */
|
|
int
|
|
Py_MakePendingCalls(void)
|
|
{
|
|
assert(PyGILState_Check());
|
|
|
|
PyThreadState *tstate = _PyThreadState_GET();
|
|
assert(is_tstate_valid(tstate));
|
|
|
|
/* Only execute pending calls on the main thread. */
|
|
if (!_Py_IsMainThread() || !_Py_IsMainInterpreter(tstate->interp)) {
|
|
return 0;
|
|
}
|
|
return _PyEval_MakePendingCalls(tstate);
|
|
}
|
|
|
|
void
|
|
_PyEval_InitState(PyInterpreterState *interp, PyThread_type_lock pending_lock)
|
|
{
|
|
_gil_initialize(&interp->_gil);
|
|
|
|
struct _pending_calls *pending = &interp->ceval.pending;
|
|
assert(pending->lock == NULL);
|
|
pending->lock = pending_lock;
|
|
}
|
|
|
|
void
|
|
_PyEval_FiniState(struct _ceval_state *ceval)
|
|
{
|
|
struct _pending_calls *pending = &ceval->pending;
|
|
if (pending->lock != NULL) {
|
|
PyThread_free_lock(pending->lock);
|
|
pending->lock = NULL;
|
|
}
|
|
}
|
|
|
|
|
|
/* Do periodic things, like check for signals and async I/0.
|
|
* We need to do reasonably frequently, but not too frequently.
|
|
* All loops should include a check of the eval breaker.
|
|
* We also check on return from any builtin function.
|
|
*
|
|
* ## More Details ###
|
|
*
|
|
* The eval loop (this function) normally executes the instructions
|
|
* of a code object sequentially. However, the runtime supports a
|
|
* number of out-of-band execution scenarios that may pause that
|
|
* sequential execution long enough to do that out-of-band work
|
|
* in the current thread using the current PyThreadState.
|
|
*
|
|
* The scenarios include:
|
|
*
|
|
* - cyclic garbage collection
|
|
* - GIL drop requests
|
|
* - "async" exceptions
|
|
* - "pending calls" (some only in the main thread)
|
|
* - signal handling (only in the main thread)
|
|
*
|
|
* When the need for one of the above is detected, the eval loop
|
|
* pauses long enough to handle the detected case. Then, if doing
|
|
* so didn't trigger an exception, the eval loop resumes executing
|
|
* the sequential instructions.
|
|
*
|
|
* To make this work, the eval loop periodically checks if any
|
|
* of the above needs to happen. The individual checks can be
|
|
* expensive if computed each time, so a while back we switched
|
|
* to using pre-computed, per-interpreter variables for the checks,
|
|
* and later consolidated that to a single "eval breaker" variable
|
|
* (now a PyInterpreterState field).
|
|
*
|
|
* For the longest time, the eval breaker check would happen
|
|
* frequently, every 5 or so times through the loop, regardless
|
|
* of what instruction ran last or what would run next. Then, in
|
|
* early 2021 (gh-18334, commit 4958f5d), we switched to checking
|
|
* the eval breaker less frequently, by hard-coding the check to
|
|
* specific places in the eval loop (e.g. certain instructions).
|
|
* The intent then was to check after returning from calls
|
|
* and on the back edges of loops.
|
|
*
|
|
* In addition to being more efficient, that approach keeps
|
|
* the eval loop from running arbitrary code between instructions
|
|
* that don't handle that well. (See gh-74174.)
|
|
*
|
|
* Currently, the eval breaker check happens on back edges in
|
|
* the control flow graph, which pretty much applies to all loops,
|
|
* and most calls.
|
|
* (See bytecodes.c for exact information.)
|
|
*
|
|
* One consequence of this approach is that it might not be obvious
|
|
* how to force any specific thread to pick up the eval breaker,
|
|
* or for any specific thread to not pick it up. Mostly this
|
|
* involves judicious uses of locks and careful ordering of code,
|
|
* while avoiding code that might trigger the eval breaker
|
|
* until so desired.
|
|
*/
|
|
int
|
|
_Py_HandlePending(PyThreadState *tstate)
|
|
{
|
|
_PyRuntimeState * const runtime = &_PyRuntime;
|
|
struct _ceval_runtime_state *ceval = &runtime->ceval;
|
|
struct _ceval_state *interp_ceval_state = &tstate->interp->ceval;
|
|
|
|
/* Pending signals */
|
|
if (_Py_atomic_load_relaxed_int32(&ceval->signals_pending)) {
|
|
if (handle_signals(tstate) != 0) {
|
|
return -1;
|
|
}
|
|
}
|
|
|
|
/* Pending calls */
|
|
if (maybe_has_pending_calls(tstate->interp)) {
|
|
if (make_pending_calls(tstate->interp) != 0) {
|
|
return -1;
|
|
}
|
|
}
|
|
|
|
/* GC scheduled to run */
|
|
if (_Py_atomic_load_relaxed_int32(&interp_ceval_state->gc_scheduled)) {
|
|
_Py_atomic_store_relaxed(&interp_ceval_state->gc_scheduled, 0);
|
|
COMPUTE_EVAL_BREAKER(tstate->interp, ceval, interp_ceval_state);
|
|
_Py_RunGC(tstate);
|
|
}
|
|
|
|
/* GIL drop request */
|
|
if (_Py_atomic_load_relaxed_int32(&interp_ceval_state->gil_drop_request)) {
|
|
/* Give another thread a chance */
|
|
if (_PyThreadState_SwapNoGIL(NULL) != tstate) {
|
|
Py_FatalError("tstate mix-up");
|
|
}
|
|
drop_gil(interp_ceval_state, tstate);
|
|
|
|
/* Other threads may run now */
|
|
|
|
take_gil(tstate);
|
|
|
|
if (_PyThreadState_SwapNoGIL(tstate) != NULL) {
|
|
Py_FatalError("orphan tstate");
|
|
}
|
|
}
|
|
|
|
/* Check for asynchronous exception. */
|
|
if (tstate->async_exc != NULL) {
|
|
PyObject *exc = tstate->async_exc;
|
|
tstate->async_exc = NULL;
|
|
UNSIGNAL_ASYNC_EXC(tstate->interp);
|
|
_PyErr_SetNone(tstate, exc);
|
|
Py_DECREF(exc);
|
|
return -1;
|
|
}
|
|
|
|
|
|
// It is possible that some of the conditions that trigger the eval breaker
|
|
// are called in a different thread than the Python thread. An example of
|
|
// this is bpo-42296: On Windows, _PyEval_SignalReceived() can be called in
|
|
// a different thread than the Python thread, in which case
|
|
// _Py_ThreadCanHandleSignals() is wrong. Recompute eval_breaker in the
|
|
// current Python thread with the correct _Py_ThreadCanHandleSignals()
|
|
// value. It prevents to interrupt the eval loop at every instruction if
|
|
// the current Python thread cannot handle signals (if
|
|
// _Py_ThreadCanHandleSignals() is false).
|
|
COMPUTE_EVAL_BREAKER(tstate->interp, ceval, interp_ceval_state);
|
|
|
|
return 0;
|
|
}
|
|
|