githubmirror/cpython

Python/tracemalloc.c
1 489 строк37 KB
Victor Stinner
[3.14] gh-144763: Fix race conditions in tracemalloc (#144779) (#144965)
18 фев 2026, 22:55
18 фев 2026, 22:55f67cf83
#include "Python.h"
#include "pycore_fileutils.h"     // _Py_write_noraise()
#include "pycore_gc.h"            // PyGC_Head
#include "pycore_hashtable.h"     // _Py_hashtable_t
#include "pycore_initconfig.h"    // _PyStatus_NO_MEMORY()
#include "pycore_interpframe.h"   // _PyInterpreterFrame
#include "pycore_lock.h"          // PyMutex_LockFlags()
#include "pycore_object.h"        // _PyType_PreHeaderSize()
#include "pycore_pymem.h"         // _Py_tracemalloc_config
#include "pycore_runtime.h"       // _Py_ID()
#include "pycore_traceback.h"     // _Py_DumpASCII()

#include <stdlib.h>               // malloc()

#define tracemalloc_config _PyRuntime.tracemalloc.config

_Py_DECLARE_STR(anon_unknown, "<unknown>");

/* Forward declaration */
static void* raw_malloc(size_t size);
static void raw_free(void *ptr);
static int _PyTraceMalloc_TraceRef(PyObject *op, PyRefTracerEvent event,
                                   void* Py_UNUSED(ignore));

#ifdef Py_DEBUG
#  define TRACE_DEBUG
#endif

#define TO_PTR(key) ((const void *)(uintptr_t)(key))
#define FROM_PTR(key) ((uintptr_t)(key))

#define allocators _PyRuntime.tracemalloc.allocators


/* This lock is needed because tracemalloc_free() is called without
   the GIL held from PyMem_RawFree(). It cannot acquire the lock because it
   would introduce a deadlock in _PyThreadState_DeleteCurrent(). */
#define tables_lock _PyRuntime.tracemalloc.tables_lock
#define TABLES_LOCK() PyMutex_LockFlags(&tables_lock, _Py_LOCK_DONT_DETACH)
#define TABLES_UNLOCK() PyMutex_Unlock(&tables_lock)


#define DEFAULT_DOMAIN 0

typedef struct tracemalloc_frame frame_t;
typedef struct tracemalloc_traceback traceback_t;

#define TRACEBACK_SIZE(NFRAME) \
        (sizeof(traceback_t) + sizeof(frame_t) * (NFRAME - 1))

static const int MAX_NFRAME = UINT16_MAX;


#define tracemalloc_empty_traceback _PyRuntime.tracemalloc.empty_traceback


/* Trace of a memory block */
typedef struct {
    /* Size of the memory block in bytes */
    size_t size;

    /* Traceback where the memory block was allocated */
    traceback_t *traceback;
} trace_t;


#define tracemalloc_traced_memory _PyRuntime.tracemalloc.traced_memory
#define tracemalloc_peak_traced_memory _PyRuntime.tracemalloc.peak_traced_memory
#define tracemalloc_filenames _PyRuntime.tracemalloc.filenames
#define tracemalloc_traceback _PyRuntime.tracemalloc.traceback
#define tracemalloc_tracebacks _PyRuntime.tracemalloc.tracebacks
#define tracemalloc_traces _PyRuntime.tracemalloc.traces
#define tracemalloc_domains _PyRuntime.tracemalloc.domains


#ifdef TRACE_DEBUG
static void
tracemalloc_error(const char *format, ...)
{
    va_list ap;
    fprintf(stderr, "tracemalloc: ");
    va_start(ap, format);
    vfprintf(stderr, format, ap);
    va_end(ap);
    fprintf(stderr, "\n");
    fflush(stderr);
}
#endif


#define tracemalloc_reentrant_key _PyRuntime.tracemalloc.reentrant_key

/* Any non-NULL pointer can be used */
#define REENTRANT Py_True

static int
get_reentrant(void)
{
    assert(PyThread_tss_is_created(&tracemalloc_reentrant_key));

    void *ptr = PyThread_tss_get(&tracemalloc_reentrant_key);
    if (ptr != NULL) {
        assert(ptr == REENTRANT);
        return 1;
    }
    else {
        return 0;
    }
}

static void
set_reentrant(int reentrant)
{
    assert(reentrant == 0 || reentrant == 1);
    assert(PyThread_tss_is_created(&tracemalloc_reentrant_key));

    if (reentrant) {
        assert(!get_reentrant());
        PyThread_tss_set(&tracemalloc_reentrant_key, REENTRANT);
    }
    else {
        assert(get_reentrant());
        PyThread_tss_set(&tracemalloc_reentrant_key, NULL);
    }
}


static Py_uhash_t
hashtable_hash_pyobject(const void *key)
{
    PyObject *obj = (PyObject *)key;
    return PyObject_Hash(obj);
}


static int
hashtable_compare_unicode(const void *key1, const void *key2)
{
    PyObject *obj1 = (PyObject *)key1;
    PyObject *obj2 = (PyObject *)key2;
    if (obj1 != NULL && obj2 != NULL) {
        return (PyUnicode_Compare(obj1, obj2) == 0);
    }
    else {
        return obj1 == obj2;
    }
}


static Py_uhash_t
hashtable_hash_uint(const void *key_raw)
{
    unsigned int key = (unsigned int)FROM_PTR(key_raw);
    return (Py_uhash_t)key;
}


static _Py_hashtable_t *
hashtable_new(_Py_hashtable_hash_func hash_func,
              _Py_hashtable_compare_func compare_func,
              _Py_hashtable_destroy_func key_destroy_func,
              _Py_hashtable_destroy_func value_destroy_func)
{
    _Py_hashtable_allocator_t hashtable_alloc = {malloc, free};
    return _Py_hashtable_new_full(hash_func, compare_func,
                                  key_destroy_func, value_destroy_func,
                                  &hashtable_alloc);
}


static void*
raw_malloc(size_t size)
{
    return allocators.raw.malloc(allocators.raw.ctx, size);
}

static void
raw_free(void *ptr)
{
    allocators.raw.free(allocators.raw.ctx, ptr);
}


static Py_uhash_t
hashtable_hash_traceback(const void *key)
{
    const traceback_t *traceback = (const traceback_t *)key;
    return traceback->hash;
}


static int
hashtable_compare_traceback(const void *key1, const void *key2)
{
    const traceback_t *traceback1 = (const traceback_t *)key1;
    const traceback_t *traceback2 = (const traceback_t *)key2;

    if (traceback1->nframe != traceback2->nframe) {
        return 0;
    }
    if (traceback1->total_nframe != traceback2->total_nframe) {
        return 0;
    }

    for (int i=0; i < traceback1->nframe; i++) {
        const frame_t *frame1 = &traceback1->frames[i];
        const frame_t *frame2 = &traceback2->frames[i];

        if (frame1->lineno != frame2->lineno) {
            return 0;
        }
        if (frame1->filename != frame2->filename) {
            assert(PyUnicode_Compare(frame1->filename, frame2->filename) != 0);
            return 0;
        }
    }
    return 1;
}


static void
tracemalloc_get_frame(_PyInterpreterFrame *pyframe, frame_t *frame)
{
    assert(PyStackRef_CodeCheck(pyframe->f_executable));
    frame->filename = &_Py_STR(anon_unknown);

    int lineno = -1;
    PyCodeObject *code = _PyFrame_GetCode(pyframe);
    // PyUnstable_InterpreterFrame_GetLine() cannot but used, since it uses
    // a critical section which can trigger a deadlock.
    int lasti = _PyFrame_SafeGetLasti(pyframe);
    if (lasti >= 0) {
        lineno = _PyCode_SafeAddr2Line(code, lasti);
    }
    if (lineno < 0) {
        lineno = 0;
    }
    frame->lineno = (unsigned int)lineno;

    PyObject *filename = code->co_filename;
    if (filename == NULL) {
#ifdef TRACE_DEBUG
        tracemalloc_error("failed to get the filename of the code object");
#endif
        return;
    }

    if (!PyUnicode_Check(filename)) {
#ifdef TRACE_DEBUG
        tracemalloc_error("filename is not a unicode string");
#endif
        return;
    }

    /* intern the filename */
    _Py_hashtable_entry_t *entry;
    entry = _Py_hashtable_get_entry(tracemalloc_filenames, filename);
    if (entry != NULL) {
        filename = (PyObject *)entry->key;
    }
    else {
        /* tracemalloc_filenames is responsible to keep a reference
           to the filename */
        if (_Py_hashtable_set(tracemalloc_filenames, Py_NewRef(filename),
                              NULL) < 0) {
            Py_DECREF(filename);
#ifdef TRACE_DEBUG
            tracemalloc_error("failed to intern the filename");
#endif
            return;
        }
    }

    /* the tracemalloc_filenames table keeps a reference to the filename */
    frame->filename = filename;
}


static Py_uhash_t
traceback_hash(traceback_t *traceback)
{
    /* code based on tuple_hash() of Objects/tupleobject.c */
    Py_uhash_t x, y;  /* Unsigned for defined overflow behavior. */
    int len = traceback->nframe;
    Py_uhash_t mult = PyHASH_MULTIPLIER;
    frame_t *frame;

    x = 0x345678UL;
    frame = traceback->frames;
    while (--len >= 0) {
        y = (Py_uhash_t)PyObject_Hash(frame->filename);
        y ^= (Py_uhash_t)frame->lineno;
        frame++;

        x = (x ^ y) * mult;
        /* the cast might truncate len; that doesn't change hash stability */
        mult += (Py_uhash_t)(82520UL + len + len);
    }
    x ^= traceback->total_nframe;
    x += 97531UL;
    return x;
}


static void
traceback_get_frames(traceback_t *traceback)
{
    PyThreadState *tstate = _PyThreadState_GET();
    assert(tstate != NULL);

    _PyInterpreterFrame *pyframe = _PyThreadState_GetFrame(tstate);
    while (pyframe) {
        if (traceback->nframe < tracemalloc_config.max_nframe) {
            tracemalloc_get_frame(pyframe, &traceback->frames[traceback->nframe]);
            assert(traceback->frames[traceback->nframe].filename != NULL);
            traceback->nframe++;
        }
        if (traceback->total_nframe < UINT16_MAX) {
            traceback->total_nframe++;
        }
        pyframe = _PyFrame_GetFirstComplete(pyframe->previous);
    }
}


static traceback_t *
traceback_new(void)
{
    traceback_t *traceback;
    _Py_hashtable_entry_t *entry;

    _Py_AssertHoldsTstate();

    /* get frames */
    traceback = tracemalloc_traceback;
    traceback->nframe = 0;
    traceback->total_nframe = 0;
    traceback_get_frames(traceback);
    if (traceback->nframe == 0)
        return &tracemalloc_empty_traceback;
    traceback->hash = traceback_hash(traceback);

    /* intern the traceback */
    entry = _Py_hashtable_get_entry(tracemalloc_tracebacks, traceback);
    if (entry != NULL) {
        traceback = (traceback_t *)entry->key;
    }
    else {
        traceback_t *copy;
        size_t traceback_size;

        traceback_size = TRACEBACK_SIZE(traceback->nframe);

        copy = raw_malloc(traceback_size);
        if (copy == NULL) {
#ifdef TRACE_DEBUG
            tracemalloc_error("failed to intern the traceback: malloc failed");
#endif
            return NULL;
        }
        memcpy(copy, traceback, traceback_size);

        if (_Py_hashtable_set(tracemalloc_tracebacks, copy, NULL) < 0) {
            raw_free(copy);
#ifdef TRACE_DEBUG
            tracemalloc_error("failed to intern the traceback: putdata failed");
#endif
            return NULL;
        }
        traceback = copy;
    }
    return traceback;
}


static _Py_hashtable_t*
tracemalloc_create_traces_table(void)
{
    return hashtable_new(_Py_hashtable_hash_ptr,
                         _Py_hashtable_compare_direct,
                         NULL, raw_free);
}


static void
tracemalloc_destroy_domain(void *value)
{
    _Py_hashtable_t *ht = (_Py_hashtable_t*)value;
    _Py_hashtable_destroy(ht);
}


static _Py_hashtable_t*
tracemalloc_create_domains_table(void)
{
    return hashtable_new(hashtable_hash_uint,
                         _Py_hashtable_compare_direct,
                         NULL,
                         tracemalloc_destroy_domain);
}


static _Py_hashtable_t*
tracemalloc_get_traces_table(unsigned int domain)
{
    if (domain == DEFAULT_DOMAIN) {
        return tracemalloc_traces;
    }
    else {
        return _Py_hashtable_get(tracemalloc_domains, TO_PTR(domain));
    }
}


static void
tracemalloc_remove_trace_unlocked(unsigned int domain, uintptr_t ptr)
{
    assert(tracemalloc_config.tracing);

    _Py_hashtable_t *traces = tracemalloc_get_traces_table(domain);
    if (!traces) {
        return;
    }

    trace_t *trace = _Py_hashtable_steal(traces, TO_PTR(ptr));
    if (!trace) {
        return;
    }
    assert(tracemalloc_traced_memory >= trace->size);
    tracemalloc_traced_memory -= trace->size;
    raw_free(trace);
}

#define REMOVE_TRACE(ptr) \
    tracemalloc_remove_trace_unlocked(DEFAULT_DOMAIN, (uintptr_t)(ptr))


static int
tracemalloc_add_trace_unlocked(unsigned int domain, uintptr_t ptr,
                               size_t size)
{
    assert(tracemalloc_config.tracing);

    traceback_t *traceback = traceback_new();
    if (traceback == NULL) {
        return -1;
    }

    _Py_hashtable_t *traces = tracemalloc_get_traces_table(domain);
    if (traces == NULL) {
        traces = tracemalloc_create_traces_table();
        if (traces == NULL) {
            return -1;
        }

        if (_Py_hashtable_set(tracemalloc_domains, TO_PTR(domain), traces) < 0) {
            _Py_hashtable_destroy(traces);
            return -1;
        }
    }

    trace_t *trace = _Py_hashtable_get(traces, TO_PTR(ptr));
    if (trace != NULL) {
        /* the memory block is already tracked */
        assert(tracemalloc_traced_memory >= trace->size);
        tracemalloc_traced_memory -= trace->size;

        trace->size = size;
        trace->traceback = traceback;
    }
    else {
        trace = raw_malloc(sizeof(trace_t));
        if (trace == NULL) {
            return -1;
        }
        trace->size = size;
        trace->traceback = traceback;

        int res = _Py_hashtable_set(traces, TO_PTR(ptr), trace);
        if (res != 0) {
            raw_free(trace);
            return res;
        }
    }

    assert(tracemalloc_traced_memory <= SIZE_MAX - size);
    tracemalloc_traced_memory += size;
    if (tracemalloc_traced_memory > tracemalloc_peak_traced_memory) {
        tracemalloc_peak_traced_memory = tracemalloc_traced_memory;
    }
    return 0;
}

#define ADD_TRACE(ptr, size) \
    tracemalloc_add_trace_unlocked(DEFAULT_DOMAIN, (uintptr_t)(ptr), size)


static void*
tracemalloc_alloc(int need_gil, int use_calloc,
                  void *ctx, size_t nelem, size_t elsize)
{
    assert(elsize == 0 || nelem <= SIZE_MAX / elsize);

    int reentrant = get_reentrant();

    // Ignore reentrant call.
    //
    // For example, PyObjet_Malloc() calls
    // PyMem_Malloc() for allocations larger than 512 bytes: don't trace the
    // same memory allocation twice.
    //
    // If reentrant calls are not ignored, PyGILState_Ensure() can call
    // PyMem_RawMalloc() which would call PyGILState_Ensure() again in a loop.
    if (!reentrant) {
        set_reentrant(1);
    }

    PyMemAllocatorEx *alloc = (PyMemAllocatorEx *)ctx;
    void *ptr;
    if (use_calloc) {
        ptr = alloc->calloc(alloc->ctx, nelem, elsize);
    }
    else {
        ptr = alloc->malloc(alloc->ctx, nelem * elsize);
    }

    if (ptr == NULL) {
        goto done;
    }
    if (reentrant) {
        goto done;
    }

    PyGILState_STATE gil_state;
    if (need_gil) {
        gil_state = PyGILState_Ensure();
    }
    TABLES_LOCK();

    if (tracemalloc_config.tracing) {
        if (ADD_TRACE(ptr, nelem * elsize) < 0) {
            // Failed to allocate a trace for the new memory block
            alloc->free(alloc->ctx, ptr);
            ptr = NULL;
        }
    }
    // else: gh-128679: tracemalloc.stop() was called by another thread

    TABLES_UNLOCK();
    if (need_gil) {
        PyGILState_Release(gil_state);
    }

done:
    if (!reentrant) {
        set_reentrant(0);
    }
    return ptr;
}


static void*
tracemalloc_realloc(int need_gil, void *ctx, void *ptr, size_t new_size)
{
    int reentrant = get_reentrant();

    // Ignore reentrant call. PyObjet_Realloc() calls PyMem_Realloc() for
    // allocations larger than 512 bytes: don't trace the same memory block
    // twice.
    if (!reentrant) {
        set_reentrant(1);
    }

    PyMemAllocatorEx *alloc = (PyMemAllocatorEx *)ctx;
    void *ptr2 = alloc->realloc(alloc->ctx, ptr, new_size);

    if (ptr2 == NULL) {
        goto done;
    }
    if (reentrant) {
        goto done;
    }

    PyGILState_STATE gil_state;
    if (need_gil) {
        gil_state = PyGILState_Ensure();
    }
    TABLES_LOCK();

    if (!tracemalloc_config.tracing) {
        // gh-128679: tracemalloc.stop() was called by another thread
        goto unlock;
    }

    if (ptr != NULL) {
        // An existing memory block has been resized

        // tracemalloc_add_trace_unlocked() updates the trace if there is
        // already a trace at address ptr2.
        if (ptr2 != ptr) {
            REMOVE_TRACE(ptr);
        }

        if (ADD_TRACE(ptr2, new_size) < 0) {
            // Memory allocation failed. The error cannot be reported to the
            // caller, because realloc() already have shrunk the memory block
            // and so removed bytes.
            //
            // This case is very unlikely: a hash entry has just been released,
            // so the hash table should have at least one free entry.
            //
            // The GIL and the table lock ensures that only one thread is
            // allocating memory.
            Py_FatalError("tracemalloc_realloc() failed to allocate a trace");
        }
    }
    else {
        // New allocation

        if (ADD_TRACE(ptr2, new_size) < 0) {
            // Failed to allocate a trace for the new memory block
            alloc->free(alloc->ctx, ptr2);
            ptr2 = NULL;
        }
    }

unlock:
    TABLES_UNLOCK();
    if (need_gil) {
        PyGILState_Release(gil_state);
    }

done:
    if (!reentrant) {
        set_reentrant(0);
    }
    return ptr2;
}


static void
tracemalloc_free(void *ctx, void *ptr)
{
    if (ptr == NULL) {
        return;
    }

    PyMemAllocatorEx *alloc = (PyMemAllocatorEx *)ctx;
    alloc->free(alloc->ctx, ptr);

    if (get_reentrant()) {
        return;
    }

    TABLES_LOCK();

    if (tracemalloc_config.tracing) {
        REMOVE_TRACE(ptr);
    }
    // else: gh-128679: tracemalloc.stop() was called by another thread

    TABLES_UNLOCK();
}


static void*
tracemalloc_malloc_gil(void *ctx, size_t size)
{
    return tracemalloc_alloc(0, 0, ctx, 1, size);
}


static void*
tracemalloc_calloc_gil(void *ctx, size_t nelem, size_t elsize)
{
    return tracemalloc_alloc(0, 1, ctx, nelem, elsize);
}


static void*
tracemalloc_realloc_gil(void *ctx, void *ptr, size_t new_size)
{
    return tracemalloc_realloc(0, ctx, ptr, new_size);
}


static void*
tracemalloc_raw_malloc(void *ctx, size_t size)
{
    return tracemalloc_alloc(1, 0, ctx, 1, size);
}


static void*
tracemalloc_raw_calloc(void *ctx, size_t nelem, size_t elsize)
{
    return tracemalloc_alloc(1, 1, ctx, nelem, elsize);
}


static void*
tracemalloc_raw_realloc(void *ctx, void *ptr, size_t new_size)
{
    return tracemalloc_realloc(1, ctx, ptr, new_size);
}


static void
tracemalloc_clear_filename(void *value)
{
    PyObject *filename = (PyObject *)value;
    Py_DECREF(filename);
}


static void
tracemalloc_clear_traces_unlocked(void)
{
    // Clearing tracemalloc_filenames requires the GIL to call Py_DECREF()
    _Py_AssertHoldsTstate();

    set_reentrant(1);

    _Py_hashtable_clear(tracemalloc_traces);
    _Py_hashtable_clear(tracemalloc_domains);
    _Py_hashtable_clear(tracemalloc_tracebacks);
    _Py_hashtable_clear(tracemalloc_filenames);

    tracemalloc_traced_memory = 0;
    tracemalloc_peak_traced_memory = 0;

    set_reentrant(0);
}


PyStatus
_PyTraceMalloc_Init(void)
{
    assert(tracemalloc_config.initialized == TRACEMALLOC_NOT_INITIALIZED);

    PyMem_GetAllocator(PYMEM_DOMAIN_RAW, &allocators.raw);

    if (PyThread_tss_create(&tracemalloc_reentrant_key) != 0) {
        return _PyStatus_NO_MEMORY();
    }

    tracemalloc_filenames = hashtable_new(hashtable_hash_pyobject,
                                          hashtable_compare_unicode,
                                          tracemalloc_clear_filename, NULL);

    tracemalloc_tracebacks = hashtable_new(hashtable_hash_traceback,
                                           hashtable_compare_traceback,
                                           raw_free, NULL);

    tracemalloc_traces = tracemalloc_create_traces_table();
    tracemalloc_domains = tracemalloc_create_domains_table();

    if (tracemalloc_filenames == NULL || tracemalloc_tracebacks == NULL
       || tracemalloc_traces == NULL || tracemalloc_domains == NULL)
    {
        return _PyStatus_NO_MEMORY();
    }

    tracemalloc_empty_traceback.nframe = 1;
    tracemalloc_empty_traceback.total_nframe = 1;
    /* borrowed reference */
    tracemalloc_empty_traceback.frames[0].filename = &_Py_STR(anon_unknown);
    tracemalloc_empty_traceback.frames[0].lineno = 0;
    tracemalloc_empty_traceback.hash = traceback_hash(&tracemalloc_empty_traceback);

    tracemalloc_config.initialized = TRACEMALLOC_INITIALIZED;
    return _PyStatus_OK();
}


static void
tracemalloc_deinit(void)
{
    if (tracemalloc_config.initialized != TRACEMALLOC_INITIALIZED)
        return;
    tracemalloc_config.initialized = TRACEMALLOC_FINALIZED;

    _PyTraceMalloc_Stop();

    /* destroy hash tables */
    _Py_hashtable_destroy(tracemalloc_domains);
    _Py_hashtable_destroy(tracemalloc_traces);
    _Py_hashtable_destroy(tracemalloc_tracebacks);
    _Py_hashtable_destroy(tracemalloc_filenames);

    PyThread_tss_delete(&tracemalloc_reentrant_key);
}


int
_PyTraceMalloc_Start(int max_nframe)
{
    if (max_nframe < 1 || max_nframe > MAX_NFRAME) {
        PyErr_Format(PyExc_ValueError,
                     "the number of frames must be in range [1; %i]",
                     MAX_NFRAME);
        return -1;
    }

    if (_PyTraceMalloc_IsTracing()) {
        /* hooks already installed: do nothing */
        return 0;
    }

    tracemalloc_config.max_nframe = max_nframe;

    /* allocate a buffer to store a new traceback */
    size_t size = TRACEBACK_SIZE(max_nframe);
    assert(tracemalloc_traceback == NULL);
    tracemalloc_traceback = raw_malloc(size);
    if (tracemalloc_traceback == NULL) {
        PyErr_NoMemory();
        return -1;
    }

    PyMemAllocatorEx alloc;
    alloc.malloc = tracemalloc_raw_malloc;
    alloc.calloc = tracemalloc_raw_calloc;
    alloc.realloc = tracemalloc_raw_realloc;
    alloc.free = tracemalloc_free;

    alloc.ctx = &allocators.raw;
    PyMem_GetAllocator(PYMEM_DOMAIN_RAW, &allocators.raw);
    PyMem_SetAllocator(PYMEM_DOMAIN_RAW, &alloc);

    alloc.malloc = tracemalloc_malloc_gil;
    alloc.calloc = tracemalloc_calloc_gil;
    alloc.realloc = tracemalloc_realloc_gil;
    alloc.free = tracemalloc_free;

    alloc.ctx = &allocators.mem;
    PyMem_GetAllocator(PYMEM_DOMAIN_MEM, &allocators.mem);
    PyMem_SetAllocator(PYMEM_DOMAIN_MEM, &alloc);

    alloc.ctx = &allocators.obj;
    PyMem_GetAllocator(PYMEM_DOMAIN_OBJ, &allocators.obj);
    PyMem_SetAllocator(PYMEM_DOMAIN_OBJ, &alloc);

    if (PyRefTracer_SetTracer(_PyTraceMalloc_TraceRef, NULL) < 0) {
        return -1;
    }

    /* everything is ready: start tracing Python memory allocations */
    TABLES_LOCK();
    _Py_atomic_store_int_relaxed(&tracemalloc_config.tracing, 1);
    TABLES_UNLOCK();

    return 0;
}


void
_PyTraceMalloc_Stop(void)
{
    TABLES_LOCK();

    if (!tracemalloc_config.tracing) {
        TABLES_UNLOCK();
        return;
    }

    /* stop tracing Python memory allocations */
    _Py_atomic_store_int_relaxed(&tracemalloc_config.tracing, 0);

    /* unregister the hook on memory allocators */
    PyMem_SetAllocator(PYMEM_DOMAIN_RAW, &allocators.raw);
    PyMem_SetAllocator(PYMEM_DOMAIN_MEM, &allocators.mem);
    PyMem_SetAllocator(PYMEM_DOMAIN_OBJ, &allocators.obj);

    tracemalloc_clear_traces_unlocked();

    /* release memory */
    raw_free(tracemalloc_traceback);
    tracemalloc_traceback = NULL;

    TABLES_UNLOCK();

    // Call it after TABLES_UNLOCK() since it calls _PyEval_StopTheWorldAll()
    // which would lead to a deadlock with TABLES_LOCK() which doesn't detach
    // the thread state.
    (void)PyRefTracer_SetTracer(NULL, NULL);
}



static PyObject*
frame_to_pyobject(frame_t *frame)
{
    assert(get_reentrant());

    PyObject *frame_obj = PyTuple_New(2);
    if (frame_obj == NULL) {
        return NULL;
    }

    PyTuple_SET_ITEM(frame_obj, 0, Py_NewRef(frame->filename));

    PyObject *lineno_obj = PyLong_FromUnsignedLong(frame->lineno);
    if (lineno_obj == NULL) {
        Py_DECREF(frame_obj);
        return NULL;
    }
    PyTuple_SET_ITEM(frame_obj, 1, lineno_obj);

    return frame_obj;
}


static PyObject*
traceback_to_pyobject(traceback_t *traceback, _Py_hashtable_t *intern_table)
{
    PyObject *frames;
    if (intern_table != NULL) {
        frames = _Py_hashtable_get(intern_table, (const void *)traceback);
        if (frames) {
            return Py_NewRef(frames);
        }
    }

    frames = PyTuple_New(traceback->nframe);
    if (frames == NULL) {
        return NULL;
    }

    for (int i=0; i < traceback->nframe; i++) {
        PyObject *frame = frame_to_pyobject(&traceback->frames[i]);
        if (frame == NULL) {
            Py_DECREF(frames);
            return NULL;
        }
        PyTuple_SET_ITEM(frames, i, frame);
    }

    if (intern_table != NULL) {
        if (_Py_hashtable_set(intern_table, traceback, frames) < 0) {
            Py_DECREF(frames);
            PyErr_NoMemory();
            return NULL;
        }
        /* intern_table keeps a new reference to frames */
        Py_INCREF(frames);
    }
    return frames;
}


static PyObject*
trace_to_pyobject(unsigned int domain, const trace_t *trace,
                  _Py_hashtable_t *intern_tracebacks)
{
    assert(get_reentrant());

    PyObject *trace_obj = PyTuple_New(4);
    if (trace_obj == NULL) {
        return NULL;
    }

    PyObject *obj = PyLong_FromSize_t(domain);
    if (obj == NULL) {
        Py_DECREF(trace_obj);
        return NULL;
    }
    PyTuple_SET_ITEM(trace_obj, 0, obj);

    obj = PyLong_FromSize_t(trace->size);
    if (obj == NULL) {
        Py_DECREF(trace_obj);
        return NULL;
    }
    PyTuple_SET_ITEM(trace_obj, 1, obj);

    obj = traceback_to_pyobject(trace->traceback, intern_tracebacks);
    if (obj == NULL) {
        Py_DECREF(trace_obj);
        return NULL;
    }
    PyTuple_SET_ITEM(trace_obj, 2, obj);

    obj = PyLong_FromUnsignedLong(trace->traceback->total_nframe);
    if (obj == NULL) {
        Py_DECREF(trace_obj);
        return NULL;
    }
    PyTuple_SET_ITEM(trace_obj, 3, obj);

    return trace_obj;
}


typedef struct {
    _Py_hashtable_t *traces;
    _Py_hashtable_t *domains;
    _Py_hashtable_t *tracebacks;
    PyObject *list;
    unsigned int domain;
} get_traces_t;


static int
tracemalloc_copy_trace(_Py_hashtable_t *traces,
                       const void *key, const void *value,
                       void *user_data)
{
    _Py_hashtable_t *traces2 = (_Py_hashtable_t *)user_data;
    trace_t *trace = (trace_t *)value;

    trace_t *trace2 = raw_malloc(sizeof(trace_t));
    if (trace2 == NULL) {
        return -1;
    }
    *trace2 = *trace;
    if (_Py_hashtable_set(traces2, key, trace2) < 0) {
        raw_free(trace2);
        return -1;
    }
    return 0;
}


static _Py_hashtable_t*
tracemalloc_copy_traces(_Py_hashtable_t *traces)
{
    _Py_hashtable_t *traces2 = tracemalloc_create_traces_table();
    if (traces2 == NULL) {
        return NULL;
    }

    int err = _Py_hashtable_foreach(traces,
                                    tracemalloc_copy_trace,
                                    traces2);
    if (err) {
        _Py_hashtable_destroy(traces2);
        return NULL;
    }
    return traces2;
}


static int
tracemalloc_copy_domain(_Py_hashtable_t *domains,
                        const void *key, const void *value,
                        void *user_data)
{
    _Py_hashtable_t *domains2 = (_Py_hashtable_t *)user_data;
    unsigned int domain = (unsigned int)FROM_PTR(key);
    _Py_hashtable_t *traces = (_Py_hashtable_t *)value;

    _Py_hashtable_t *traces2 = tracemalloc_copy_traces(traces);
    if (traces2 == NULL) {
        return -1;
    }
    if (_Py_hashtable_set(domains2, TO_PTR(domain), traces2) < 0) {
        _Py_hashtable_destroy(traces2);
        return -1;
    }
    return 0;
}


static _Py_hashtable_t*
tracemalloc_copy_domains(_Py_hashtable_t *domains)
{
    _Py_hashtable_t *domains2 = tracemalloc_create_domains_table();
    if (domains2 == NULL) {
        return NULL;
    }

    int err = _Py_hashtable_foreach(domains,
                                    tracemalloc_copy_domain,
                                    domains2);
    if (err) {
        _Py_hashtable_destroy(domains2);
        return NULL;
    }
    return domains2;
}


static int
tracemalloc_get_traces_fill(_Py_hashtable_t *traces,
                            const void *key, const void *value,
                            void *user_data)
{
    get_traces_t *get_traces = user_data;
    const trace_t *trace = (const trace_t *)value;

    PyObject *tuple = trace_to_pyobject(get_traces->domain, trace,
                                        get_traces->tracebacks);
    if (tuple == NULL) {
        return 1;
    }

    int res = PyList_Append(get_traces->list, tuple);
    Py_DECREF(tuple);
    if (res < 0) {
        return 1;
    }
    return 0;
}


static int
tracemalloc_get_traces_domain(_Py_hashtable_t *domains,
                              const void *key, const void *value,
                              void *user_data)
{
    get_traces_t *get_traces = user_data;
    unsigned int domain = (unsigned int)FROM_PTR(key);
    _Py_hashtable_t *traces = (_Py_hashtable_t *)value;

    get_traces->domain = domain;
    return _Py_hashtable_foreach(traces,
                                 tracemalloc_get_traces_fill,
                                 get_traces);
}


static void
tracemalloc_pyobject_decref(void *value)
{
    PyObject *obj = (PyObject *)value;
    Py_DECREF(obj);
}


static traceback_t*
tracemalloc_get_traceback_unlocked(unsigned int domain, uintptr_t ptr)
{
    if (!tracemalloc_config.tracing) {
        return NULL;
    }

    _Py_hashtable_t *traces = tracemalloc_get_traces_table(domain);
    if (!traces) {
        return NULL;
    }

    trace_t *trace = _Py_hashtable_get(traces, TO_PTR(ptr));
    if (!trace) {
        return NULL;
    }
    return trace->traceback;
}


#define PUTS(fd, str) (void)_Py_write_noraise(fd, str, (int)strlen(str))

static void
_PyMem_DumpFrame(int fd, frame_t * frame)
{
    PUTS(fd, "  File \"");
    _Py_DumpASCII(fd, frame->filename);
    PUTS(fd, "\", line ");
    _Py_DumpDecimal(fd, frame->lineno);
    PUTS(fd, "\n");
}

/* Dump the traceback where a memory block was allocated into file descriptor
   fd. The function may block on TABLES_LOCK() but it is unlikely. */
void
_PyMem_DumpTraceback(int fd, const void *ptr)
{
    TABLES_LOCK();
    if (!tracemalloc_config.tracing) {
        PUTS(fd, "Enable tracemalloc to get the memory block "
                 "allocation traceback\n\n");
        goto done;
    }

    traceback_t *traceback;
    traceback = tracemalloc_get_traceback_unlocked(DEFAULT_DOMAIN,
                                                   (uintptr_t)ptr);
    if (traceback == NULL) {
        goto done;
    }

    PUTS(fd, "Memory block allocated at (most recent call first):\n");
    for (int i=0; i < traceback->nframe; i++) {
        _PyMem_DumpFrame(fd, &traceback->frames[i]);
    }
    PUTS(fd, "\n");

done:
    TABLES_UNLOCK();
}

#undef PUTS


static int
tracemalloc_get_tracemalloc_memory_cb(_Py_hashtable_t *domains,
                                      const void *key, const void *value,
                                      void *user_data)
{
    const _Py_hashtable_t *traces = value;
    size_t *size = (size_t*)user_data;
    *size += _Py_hashtable_size(traces);
    return 0;
}

int
PyTraceMalloc_Track(unsigned int domain, uintptr_t ptr,
                    size_t size)
{
    if (_Py_atomic_load_int_relaxed(&tracemalloc_config.tracing) == 0) {
        /* tracemalloc is not tracing: do nothing */
        return -2;
    }
    PyGILState_STATE gil_state = PyGILState_Ensure();
    TABLES_LOCK();

    int result;
    if (tracemalloc_config.tracing) {
        result = tracemalloc_add_trace_unlocked(domain, ptr, size);
    }
    else {
        /* tracemalloc is not tracing: do nothing */
        result = -2;
    }

    TABLES_UNLOCK();
    PyGILState_Release(gil_state);
    return result;
}


int
PyTraceMalloc_Untrack(unsigned int domain, uintptr_t ptr)
{
    if (_Py_atomic_load_int_relaxed(&tracemalloc_config.tracing) == 0) {
        /* tracemalloc is not tracing: do nothing */
        return -2;
    }

    TABLES_LOCK();

    int result;
    if (tracemalloc_config.tracing) {
        tracemalloc_remove_trace_unlocked(domain, ptr);
        result = 0;
    }
    else {
        /* tracemalloc is not tracing: do nothing */
        result = -2;
    }

    TABLES_UNLOCK();
    return result;
}


void
_PyTraceMalloc_Fini(void)
{
    _Py_AssertHoldsTstate();
    tracemalloc_deinit();
}


/* If the object memory block is already traced, update its trace
   with the current Python traceback.

   Do nothing if tracemalloc is not tracing memory allocations
   or if the object memory block is not already traced. */
static int
_PyTraceMalloc_TraceRef(PyObject *op, PyRefTracerEvent event,
                        void* Py_UNUSED(ignore))
{
    if (event != PyRefTracer_CREATE) {
        return 0;
    }
    if (get_reentrant()) {
        return 0;
    }

    _Py_AssertHoldsTstate();
    TABLES_LOCK();

    if (!tracemalloc_config.tracing) {
        goto done;
    }

    PyTypeObject *type = Py_TYPE(op);
    const size_t presize = _PyType_PreHeaderSize(type);
    uintptr_t ptr = (uintptr_t)((char *)op - presize);

    trace_t *trace = _Py_hashtable_get(tracemalloc_traces, TO_PTR(ptr));
    if (trace != NULL) {
        /* update the traceback of the memory block */
        traceback_t *traceback = traceback_new();
        if (traceback != NULL) {
            trace->traceback = traceback;
        }
    }
    /* else: cannot track the object, its memory block size is unknown */

done:
    TABLES_UNLOCK();
    return 0;
}


PyObject*
_PyTraceMalloc_GetTraceback(unsigned int domain, uintptr_t ptr)
{
    TABLES_LOCK();

    traceback_t *traceback = tracemalloc_get_traceback_unlocked(domain, ptr);
    PyObject *result;
    if (traceback) {
        set_reentrant(1);
        result = traceback_to_pyobject(traceback, NULL);
        set_reentrant(0);
    }
    else {
        result = Py_NewRef(Py_None);
    }

    TABLES_UNLOCK();
    return result;
}

int
_PyTraceMalloc_IsTracing(void)
{
    TABLES_LOCK();
    int tracing = tracemalloc_config.tracing;
    TABLES_UNLOCK();
    return tracing;
}

void
_PyTraceMalloc_ClearTraces(void)
{
    TABLES_LOCK();
    if (tracemalloc_config.tracing) {
        tracemalloc_clear_traces_unlocked();
    }
    TABLES_UNLOCK();
}

PyObject *
_PyTraceMalloc_GetTraces(void)
{
    TABLES_LOCK();
    set_reentrant(1);

    get_traces_t get_traces;
    get_traces.domain = DEFAULT_DOMAIN;
    get_traces.traces = NULL;
    get_traces.domains = NULL;
    get_traces.tracebacks = NULL;
    get_traces.list = PyList_New(0);
    if (get_traces.list == NULL) {
        goto finally;
    }

    if (!tracemalloc_config.tracing) {
        goto finally;
    }

    /* the traceback hash table is used temporarily to intern traceback tuple
       of (filename, lineno) tuples */
    get_traces.tracebacks = hashtable_new(_Py_hashtable_hash_ptr,
                                          _Py_hashtable_compare_direct,
                                          NULL, tracemalloc_pyobject_decref);
    if (get_traces.tracebacks == NULL) {
        goto no_memory;
    }

    // Copy all traces so tracemalloc_get_traces_fill() doesn't have to disable
    // temporarily tracemalloc which would impact other threads and so would
    // miss allocations while get_traces() is called.
    get_traces.traces = tracemalloc_copy_traces(tracemalloc_traces);
    if (get_traces.traces == NULL) {
        goto no_memory;
    }

    get_traces.domains = tracemalloc_copy_domains(tracemalloc_domains);
    if (get_traces.domains == NULL) {
        goto no_memory;
    }

    // Convert traces to a list of tuples
    int err = _Py_hashtable_foreach(get_traces.traces,
                                    tracemalloc_get_traces_fill,
                                    &get_traces);
    if (!err) {
        err = _Py_hashtable_foreach(get_traces.domains,
                                    tracemalloc_get_traces_domain,
                                    &get_traces);
    }

    if (err) {
        Py_CLEAR(get_traces.list);
        goto finally;
    }
    goto finally;

no_memory:
    PyErr_NoMemory();
    Py_CLEAR(get_traces.list);
    goto finally;

finally:
    set_reentrant(0);
    TABLES_UNLOCK();

    if (get_traces.tracebacks != NULL) {
        _Py_hashtable_destroy(get_traces.tracebacks);
    }
    if (get_traces.traces != NULL) {
        _Py_hashtable_destroy(get_traces.traces);
    }
    if (get_traces.domains != NULL) {
        _Py_hashtable_destroy(get_traces.domains);
    }

    return get_traces.list;
}

PyObject *
_PyTraceMalloc_GetObjectTraceback(PyObject *obj)
/*[clinic end generated code: output=41ee0553a658b0aa input=29495f1b21c53212]*/
{
    PyTypeObject *type = Py_TYPE(obj);
    const size_t presize = _PyType_PreHeaderSize(type);
    uintptr_t ptr = (uintptr_t)((char *)obj - presize);
    return _PyTraceMalloc_GetTraceback(DEFAULT_DOMAIN, ptr);
}

int _PyTraceMalloc_GetTracebackLimit(void)
{
    return tracemalloc_config.max_nframe;
}

size_t
_PyTraceMalloc_GetMemory(void)
{
    TABLES_LOCK();
    size_t size;
    if (tracemalloc_config.tracing) {
        size = _Py_hashtable_size(tracemalloc_tracebacks);
        size += _Py_hashtable_size(tracemalloc_filenames);

        size += _Py_hashtable_size(tracemalloc_traces);
        _Py_hashtable_foreach(tracemalloc_domains,
                              tracemalloc_get_tracemalloc_memory_cb, &size);
    }
    else {
        size = 0;
    }
    TABLES_UNLOCK();
    return size;
}


PyObject *
_PyTraceMalloc_GetTracedMemory(void)
{
    TABLES_LOCK();
    Py_ssize_t traced, peak;
    if (tracemalloc_config.tracing) {
        traced = tracemalloc_traced_memory;
        peak = tracemalloc_peak_traced_memory;
    }
    else {
        traced = 0;
        peak = 0;
    }
    TABLES_UNLOCK();

    return Py_BuildValue("nn", traced, peak);
}

void
_PyTraceMalloc_ResetPeak(void)
{
    TABLES_LOCK();
    if (tracemalloc_config.tracing) {
        tracemalloc_peak_traced_memory = tracemalloc_traced_memory;
    }
    TABLES_UNLOCK();
}