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circuitpython/py/gc.c
Damien George b6b39bff47 py/gc: Make gc_lock_depth have a count per thread. 
This commit makes gc_lock_depth have one counter per thread, instead of one
global counter.  This makes threads properly independent with respect to
the GC, in particular threads can now independently lock the GC for
themselves without locking it for other threads.  It also means a given
thread can run a hard IRQ without temporarily locking the GC for all other
threads and potentially making them have MemoryError exceptions at random
locations (this really only occurs on MCUs with multiple cores and no GIL,
eg on the rp2 port).

The commit also removes protection of the GC lock/unlock functions, which
is no longer needed when the counter is per thread (and this also fixes the
cas where a hard IRQ calling gc_lock() may stall waiting for the mutex).

It also puts the check for `gc_lock_depth > 0` outside the GC mutex in
gc_alloc, gc_realloc and gc_free, to potentially prevent a hard IRQ from
waiting on a mutex if it does attempt to allocate heap memory (and putting
the check outside the GC mutex is now safe now that there is a
gc_lock_depth per thread).

Signed-off-by: Damien George <damien@micropython.org>
2021-05-10 13:07:16 +10:00

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/*
* This file is part of the MicroPython project, http://micropython.org/
*
* The MIT License (MIT)
*
* Copyright (c) 2013, 2014 Damien P. George
* Copyright (c) 2014 Paul Sokolovsky
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#include <assert.h>
#include <stdio.h>
#include <string.h>
#include "py/gc.h"
#include "py/runtime.h"
#if MICROPY_ENABLE_GC
#if MICROPY_DEBUG_VERBOSE // print debugging info
#define DEBUG_PRINT (1)
#define DEBUG_printf DEBUG_printf
#else // don't print debugging info
#define DEBUG_PRINT (0)
#define DEBUG_printf(...) (void)0
#endif
// make this 1 to dump the heap each time it changes
#define EXTENSIVE_HEAP_PROFILING (0)
// make this 1 to zero out swept memory to more eagerly
// detect untraced object still in use
#define CLEAR_ON_SWEEP (0)
#define WORDS_PER_BLOCK ((MICROPY_BYTES_PER_GC_BLOCK) / MP_BYTES_PER_OBJ_WORD)
#define BYTES_PER_BLOCK (MICROPY_BYTES_PER_GC_BLOCK)
// ATB = allocation table byte
// 0b00 = FREE -- free block
// 0b01 = HEAD -- head of a chain of blocks
// 0b10 = TAIL -- in the tail of a chain of blocks
// 0b11 = MARK -- marked head block
#define AT_FREE (0)
#define AT_HEAD (1)
#define AT_TAIL (2)
#define AT_MARK (3)
#define BLOCKS_PER_ATB (4)
#define ATB_MASK_0 (0x03)
#define ATB_MASK_1 (0x0c)
#define ATB_MASK_2 (0x30)
#define ATB_MASK_3 (0xc0)
#define ATB_0_IS_FREE(a) (((a) & ATB_MASK_0) == 0)
#define ATB_1_IS_FREE(a) (((a) & ATB_MASK_1) == 0)
#define ATB_2_IS_FREE(a) (((a) & ATB_MASK_2) == 0)
#define ATB_3_IS_FREE(a) (((a) & ATB_MASK_3) == 0)
#define BLOCK_SHIFT(block) (2 * ((block) & (BLOCKS_PER_ATB - 1)))
#define ATB_GET_KIND(block) ((MP_STATE_MEM(gc_alloc_table_start)[(block) / BLOCKS_PER_ATB] >> BLOCK_SHIFT(block)) & 3)
#define ATB_ANY_TO_FREE(block) do { MP_STATE_MEM(gc_alloc_table_start)[(block) / BLOCKS_PER_ATB] &= (~(AT_MARK << BLOCK_SHIFT(block))); } while (0)
#define ATB_FREE_TO_HEAD(block) do { MP_STATE_MEM(gc_alloc_table_start)[(block) / BLOCKS_PER_ATB] |= (AT_HEAD << BLOCK_SHIFT(block)); } while (0)
#define ATB_FREE_TO_TAIL(block) do { MP_STATE_MEM(gc_alloc_table_start)[(block) / BLOCKS_PER_ATB] |= (AT_TAIL << BLOCK_SHIFT(block)); } while (0)
#define ATB_HEAD_TO_MARK(block) do { MP_STATE_MEM(gc_alloc_table_start)[(block) / BLOCKS_PER_ATB] |= (AT_MARK << BLOCK_SHIFT(block)); } while (0)
#define ATB_MARK_TO_HEAD(block) do { MP_STATE_MEM(gc_alloc_table_start)[(block) / BLOCKS_PER_ATB] &= (~(AT_TAIL << BLOCK_SHIFT(block))); } while (0)
#define BLOCK_FROM_PTR(ptr) (((byte *)(ptr) - MP_STATE_MEM(gc_pool_start)) / BYTES_PER_BLOCK)
#define PTR_FROM_BLOCK(block) (((block) * BYTES_PER_BLOCK + (uintptr_t)MP_STATE_MEM(gc_pool_start)))
#define ATB_FROM_BLOCK(bl) ((bl) / BLOCKS_PER_ATB)
#if MICROPY_ENABLE_FINALISER
// FTB = finaliser table byte
// if set, then the corresponding block may have a finaliser
#define BLOCKS_PER_FTB (8)
#define FTB_GET(block) ((MP_STATE_MEM(gc_finaliser_table_start)[(block) / BLOCKS_PER_FTB] >> ((block) & 7)) & 1)
#define FTB_SET(block) do { MP_STATE_MEM(gc_finaliser_table_start)[(block) / BLOCKS_PER_FTB] |= (1 << ((block) & 7)); } while (0)
#define FTB_CLEAR(block) do { MP_STATE_MEM(gc_finaliser_table_start)[(block) / BLOCKS_PER_FTB] &= (~(1 << ((block) & 7))); } while (0)
#endif
#if MICROPY_PY_THREAD && !MICROPY_PY_THREAD_GIL
#define GC_ENTER() mp_thread_mutex_lock(&MP_STATE_MEM(gc_mutex), 1)
#define GC_EXIT() mp_thread_mutex_unlock(&MP_STATE_MEM(gc_mutex))
#else
#define GC_ENTER()
#define GC_EXIT()
#endif
// TODO waste less memory; currently requires that all entries in alloc_table have a corresponding block in pool
void gc_init(void *start, void *end) {
// align end pointer on block boundary
end = (void *)((uintptr_t)end & (~(BYTES_PER_BLOCK - 1)));
DEBUG_printf("Initializing GC heap: %p..%p = " UINT_FMT " bytes\n", start, end, (byte *)end - (byte *)start);
// calculate parameters for GC (T=total, A=alloc table, F=finaliser table, P=pool; all in bytes):
// T = A + F + P
// F = A * BLOCKS_PER_ATB / BLOCKS_PER_FTB
// P = A * BLOCKS_PER_ATB * BYTES_PER_BLOCK
// => T = A * (1 + BLOCKS_PER_ATB / BLOCKS_PER_FTB + BLOCKS_PER_ATB * BYTES_PER_BLOCK)
size_t total_byte_len = (byte *)end - (byte *)start;
#if MICROPY_ENABLE_FINALISER
MP_STATE_MEM(gc_alloc_table_byte_len) = total_byte_len * MP_BITS_PER_BYTE / (MP_BITS_PER_BYTE + MP_BITS_PER_BYTE * BLOCKS_PER_ATB / BLOCKS_PER_FTB + MP_BITS_PER_BYTE * BLOCKS_PER_ATB * BYTES_PER_BLOCK);
#else
MP_STATE_MEM(gc_alloc_table_byte_len) = total_byte_len / (1 + MP_BITS_PER_BYTE / 2 * BYTES_PER_BLOCK);
#endif
MP_STATE_MEM(gc_alloc_table_start) = (byte *)start;
#if MICROPY_ENABLE_FINALISER
size_t gc_finaliser_table_byte_len = (MP_STATE_MEM(gc_alloc_table_byte_len) * BLOCKS_PER_ATB + BLOCKS_PER_FTB - 1) / BLOCKS_PER_FTB;
MP_STATE_MEM(gc_finaliser_table_start) = MP_STATE_MEM(gc_alloc_table_start) + MP_STATE_MEM(gc_alloc_table_byte_len);
#endif
size_t gc_pool_block_len = MP_STATE_MEM(gc_alloc_table_byte_len) * BLOCKS_PER_ATB;
MP_STATE_MEM(gc_pool_start) = (byte *)end - gc_pool_block_len * BYTES_PER_BLOCK;
MP_STATE_MEM(gc_pool_end) = end;
#if MICROPY_ENABLE_FINALISER
assert(MP_STATE_MEM(gc_pool_start) >= MP_STATE_MEM(gc_finaliser_table_start) + gc_finaliser_table_byte_len);
#endif
// clear ATBs
memset(MP_STATE_MEM(gc_alloc_table_start), 0, MP_STATE_MEM(gc_alloc_table_byte_len));
#if MICROPY_ENABLE_FINALISER
// clear FTBs
memset(MP_STATE_MEM(gc_finaliser_table_start), 0, gc_finaliser_table_byte_len);
#endif
// set last free ATB index to start of heap
MP_STATE_MEM(gc_last_free_atb_index) = 0;
// unlock the GC
MP_STATE_THREAD(gc_lock_depth) = 0;
// allow auto collection
MP_STATE_MEM(gc_auto_collect_enabled) = 1;
#if MICROPY_GC_ALLOC_THRESHOLD
// by default, maxuint for gc threshold, effectively turning gc-by-threshold off
MP_STATE_MEM(gc_alloc_threshold) = (size_t)-1;
MP_STATE_MEM(gc_alloc_amount) = 0;
#endif
#if MICROPY_PY_THREAD && !MICROPY_PY_THREAD_GIL
mp_thread_mutex_init(&MP_STATE_MEM(gc_mutex));
#endif
DEBUG_printf("GC layout:\n");
DEBUG_printf(" alloc table at %p, length " UINT_FMT " bytes, " UINT_FMT " blocks\n", MP_STATE_MEM(gc_alloc_table_start), MP_STATE_MEM(gc_alloc_table_byte_len), MP_STATE_MEM(gc_alloc_table_byte_len) * BLOCKS_PER_ATB);
#if MICROPY_ENABLE_FINALISER
DEBUG_printf(" finaliser table at %p, length " UINT_FMT " bytes, " UINT_FMT " blocks\n", MP_STATE_MEM(gc_finaliser_table_start), gc_finaliser_table_byte_len, gc_finaliser_table_byte_len * BLOCKS_PER_FTB);
#endif
DEBUG_printf(" pool at %p, length " UINT_FMT " bytes, " UINT_FMT " blocks\n", MP_STATE_MEM(gc_pool_start), gc_pool_block_len * BYTES_PER_BLOCK, gc_pool_block_len);
}
void gc_lock(void) {
// This does not need to be atomic or have the GC mutex because:
// - each thread has its own gc_lock_depth so there are no races between threads;
// - a hard interrupt will only change gc_lock_depth during its execution, and
// upon return will restore the value of gc_lock_depth.
MP_STATE_THREAD(gc_lock_depth)++;
}
void gc_unlock(void) {
// This does not need to be atomic, See comment above in gc_lock.
MP_STATE_THREAD(gc_lock_depth)--;
}
bool gc_is_locked(void) {
return MP_STATE_THREAD(gc_lock_depth) != 0;
}
// ptr should be of type void*
#define VERIFY_PTR(ptr) ( \
((uintptr_t)(ptr) & (BYTES_PER_BLOCK - 1)) == 0 /* must be aligned on a block */ \
&& ptr >= (void *)MP_STATE_MEM(gc_pool_start) /* must be above start of pool */ \
&& ptr < (void *)MP_STATE_MEM(gc_pool_end) /* must be below end of pool */ \
)
#ifndef TRACE_MARK
#if DEBUG_PRINT
#define TRACE_MARK(block, ptr) DEBUG_printf("gc_mark(%p)\n", ptr)
#else
#define TRACE_MARK(block, ptr)
#endif
#endif
// Take the given block as the topmost block on the stack. Check all it's
// children: mark the unmarked child blocks and put those newly marked
// blocks on the stack. When all children have been checked, pop off the
// topmost block on the stack and repeat with that one.
STATIC void gc_mark_subtree(size_t block) {
// Start with the block passed in the argument.
size_t sp = 0;
for (;;) {
// work out number of consecutive blocks in the chain starting with this one
size_t n_blocks = 0;
do {
n_blocks += 1;
} while (ATB_GET_KIND(block + n_blocks) == AT_TAIL);
// check this block's children
void **ptrs = (void **)PTR_FROM_BLOCK(block);
for (size_t i = n_blocks * BYTES_PER_BLOCK / sizeof(void *); i > 0; i--, ptrs++) {
void *ptr = *ptrs;
if (VERIFY_PTR(ptr)) {
// Mark and push this pointer
size_t childblock = BLOCK_FROM_PTR(ptr);
if (ATB_GET_KIND(childblock) == AT_HEAD) {
// an unmarked head, mark it, and push it on gc stack
TRACE_MARK(childblock, ptr);
ATB_HEAD_TO_MARK(childblock);
if (sp < MICROPY_ALLOC_GC_STACK_SIZE) {
MP_STATE_MEM(gc_stack)[sp++] = childblock;
} else {
MP_STATE_MEM(gc_stack_overflow) = 1;
}
}
}
}
// Are there any blocks on the stack?
if (sp == 0) {
break; // No, stack is empty, we're done.
}
// pop the next block off the stack
block = MP_STATE_MEM(gc_stack)[--sp];
}
}
STATIC void gc_deal_with_stack_overflow(void) {
while (MP_STATE_MEM(gc_stack_overflow)) {
MP_STATE_MEM(gc_stack_overflow) = 0;
// scan entire memory looking for blocks which have been marked but not their children
for (size_t block = 0; block < MP_STATE_MEM(gc_alloc_table_byte_len) * BLOCKS_PER_ATB; block++) {
// trace (again) if mark bit set
if (ATB_GET_KIND(block) == AT_MARK) {
gc_mark_subtree(block);
}
}
}
}
STATIC void gc_sweep(void) {
#if MICROPY_PY_GC_COLLECT_RETVAL
MP_STATE_MEM(gc_collected) = 0;
#endif
// free unmarked heads and their tails
int free_tail = 0;
for (size_t block = 0; block < MP_STATE_MEM(gc_alloc_table_byte_len) * BLOCKS_PER_ATB; block++) {
switch (ATB_GET_KIND(block)) {
case AT_HEAD:
#if MICROPY_ENABLE_FINALISER
if (FTB_GET(block)) {
mp_obj_base_t *obj = (mp_obj_base_t *)PTR_FROM_BLOCK(block);
if (obj->type != NULL) {
// if the object has a type then see if it has a __del__ method
mp_obj_t dest[2];
mp_load_method_maybe(MP_OBJ_FROM_PTR(obj), MP_QSTR___del__, dest);
if (dest[0] != MP_OBJ_NULL) {
// load_method returned a method, execute it in a protected environment
#if MICROPY_ENABLE_SCHEDULER
mp_sched_lock();
#endif
mp_call_function_1_protected(dest[0], dest[1]);
#if MICROPY_ENABLE_SCHEDULER
mp_sched_unlock();
#endif
}
}
// clear finaliser flag
FTB_CLEAR(block);
}
#endif
free_tail = 1;
DEBUG_printf("gc_sweep(%p)\n", (void *)PTR_FROM_BLOCK(block));
#if MICROPY_PY_GC_COLLECT_RETVAL
MP_STATE_MEM(gc_collected)++;
#endif
// fall through to free the head
MP_FALLTHROUGH
case AT_TAIL:
if (free_tail) {
ATB_ANY_TO_FREE(block);
#if CLEAR_ON_SWEEP
memset((void *)PTR_FROM_BLOCK(block), 0, BYTES_PER_BLOCK);
#endif
}
break;
case AT_MARK:
ATB_MARK_TO_HEAD(block);
free_tail = 0;
break;
}
}
}
void gc_collect_start(void) {
GC_ENTER();
MP_STATE_THREAD(gc_lock_depth)++;
#if MICROPY_GC_ALLOC_THRESHOLD
MP_STATE_MEM(gc_alloc_amount) = 0;
#endif
MP_STATE_MEM(gc_stack_overflow) = 0;
// Trace root pointers. This relies on the root pointers being organised
// correctly in the mp_state_ctx structure. We scan nlr_top, dict_locals,
// dict_globals, then the root pointer section of mp_state_vm.
void **ptrs = (void **)(void *)&mp_state_ctx;
size_t root_start = offsetof(mp_state_ctx_t, thread.dict_locals);
size_t root_end = offsetof(mp_state_ctx_t, vm.qstr_last_chunk);
gc_collect_root(ptrs + root_start / sizeof(void *), (root_end - root_start) / sizeof(void *));
#if MICROPY_ENABLE_PYSTACK
// Trace root pointers from the Python stack.
ptrs = (void **)(void *)MP_STATE_THREAD(pystack_start);
gc_collect_root(ptrs, (MP_STATE_THREAD(pystack_cur) - MP_STATE_THREAD(pystack_start)) / sizeof(void *));
#endif
}
void gc_collect_root(void **ptrs, size_t len) {
for (size_t i = 0; i < len; i++) {
void *ptr = ptrs[i];
if (VERIFY_PTR(ptr)) {
size_t block = BLOCK_FROM_PTR(ptr);
if (ATB_GET_KIND(block) == AT_HEAD) {
// An unmarked head: mark it, and mark all its children
TRACE_MARK(block, ptr);
ATB_HEAD_TO_MARK(block);
gc_mark_subtree(block);
}
}
}
}
void gc_collect_end(void) {
gc_deal_with_stack_overflow();
gc_sweep();
MP_STATE_MEM(gc_last_free_atb_index) = 0;
MP_STATE_THREAD(gc_lock_depth)--;
GC_EXIT();
}
void gc_sweep_all(void) {
GC_ENTER();
MP_STATE_THREAD(gc_lock_depth)++;
MP_STATE_MEM(gc_stack_overflow) = 0;
gc_collect_end();
}
void gc_info(gc_info_t *info) {
GC_ENTER();
info->total = MP_STATE_MEM(gc_pool_end) - MP_STATE_MEM(gc_pool_start);
info->used = 0;
info->free = 0;
info->max_free = 0;
info->num_1block = 0;
info->num_2block = 0;
info->max_block = 0;
bool finish = false;
for (size_t block = 0, len = 0, len_free = 0; !finish;) {
size_t kind = ATB_GET_KIND(block);
switch (kind) {
case AT_FREE:
info->free += 1;
len_free += 1;
len = 0;
break;
case AT_HEAD:
info->used += 1;
len = 1;
break;
case AT_TAIL:
info->used += 1;
len += 1;
break;
case AT_MARK:
// shouldn't happen
break;
}
block++;
finish = (block == MP_STATE_MEM(gc_alloc_table_byte_len) * BLOCKS_PER_ATB);
// Get next block type if possible
if (!finish) {
kind = ATB_GET_KIND(block);
}
if (finish || kind == AT_FREE || kind == AT_HEAD) {
if (len == 1) {
info->num_1block += 1;
} else if (len == 2) {
info->num_2block += 1;
}
if (len > info->max_block) {
info->max_block = len;
}
if (finish || kind == AT_HEAD) {
if (len_free > info->max_free) {
info->max_free = len_free;
}
len_free = 0;
}
}
}
info->used *= BYTES_PER_BLOCK;
info->free *= BYTES_PER_BLOCK;
GC_EXIT();
}
void *gc_alloc(size_t n_bytes, unsigned int alloc_flags) {
bool has_finaliser = alloc_flags & GC_ALLOC_FLAG_HAS_FINALISER;
size_t n_blocks = ((n_bytes + BYTES_PER_BLOCK - 1) & (~(BYTES_PER_BLOCK - 1))) / BYTES_PER_BLOCK;
DEBUG_printf("gc_alloc(" UINT_FMT " bytes -> " UINT_FMT " blocks)\n", n_bytes, n_blocks);
// check for 0 allocation
if (n_blocks == 0) {
return NULL;
}
// check if GC is locked
if (MP_STATE_THREAD(gc_lock_depth) > 0) {
return NULL;
}
GC_ENTER();
size_t i;
size_t end_block;
size_t start_block;
size_t n_free;
int collected = !MP_STATE_MEM(gc_auto_collect_enabled);
#if MICROPY_GC_ALLOC_THRESHOLD
if (!collected && MP_STATE_MEM(gc_alloc_amount) >= MP_STATE_MEM(gc_alloc_threshold)) {
GC_EXIT();
gc_collect();
collected = 1;
GC_ENTER();
}
#endif
for (;;) {
// look for a run of n_blocks available blocks
n_free = 0;
for (i = MP_STATE_MEM(gc_last_free_atb_index); i < MP_STATE_MEM(gc_alloc_table_byte_len); i++) {
byte a = MP_STATE_MEM(gc_alloc_table_start)[i];
// *FORMAT-OFF*
if (ATB_0_IS_FREE(a)) { if (++n_free >= n_blocks) { i = i * BLOCKS_PER_ATB + 0; goto found; } } else { n_free = 0; }
if (ATB_1_IS_FREE(a)) { if (++n_free >= n_blocks) { i = i * BLOCKS_PER_ATB + 1; goto found; } } else { n_free = 0; }
if (ATB_2_IS_FREE(a)) { if (++n_free >= n_blocks) { i = i * BLOCKS_PER_ATB + 2; goto found; } } else { n_free = 0; }
if (ATB_3_IS_FREE(a)) { if (++n_free >= n_blocks) { i = i * BLOCKS_PER_ATB + 3; goto found; } } else { n_free = 0; }
// *FORMAT-ON*
}
GC_EXIT();
// nothing found!
if (collected) {
return NULL;
}
DEBUG_printf("gc_alloc(" UINT_FMT "): no free mem, triggering GC\n", n_bytes);
gc_collect();
collected = 1;
GC_ENTER();
}
// found, ending at block i inclusive
found:
// get starting and end blocks, both inclusive
end_block = i;
start_block = i - n_free + 1;
// Set last free ATB index to block after last block we found, for start of
// next scan. To reduce fragmentation, we only do this if we were looking
// for a single free block, which guarantees that there are no free blocks
// before this one. Also, whenever we free or shink a block we must check
// if this index needs adjusting (see gc_realloc and gc_free).
if (n_free == 1) {
MP_STATE_MEM(gc_last_free_atb_index) = (i + 1) / BLOCKS_PER_ATB;
}
// mark first block as used head
ATB_FREE_TO_HEAD(start_block);
// mark rest of blocks as used tail
// TODO for a run of many blocks can make this more efficient
for (size_t bl = start_block + 1; bl <= end_block; bl++) {
ATB_FREE_TO_TAIL(bl);
}
// get pointer to first block
// we must create this pointer before unlocking the GC so a collection can find it
void *ret_ptr = (void *)(MP_STATE_MEM(gc_pool_start) + start_block * BYTES_PER_BLOCK);
DEBUG_printf("gc_alloc(%p)\n", ret_ptr);
#if MICROPY_GC_ALLOC_THRESHOLD
MP_STATE_MEM(gc_alloc_amount) += n_blocks;
#endif
GC_EXIT();
#if MICROPY_GC_CONSERVATIVE_CLEAR
// be conservative and zero out all the newly allocated blocks
memset((byte *)ret_ptr, 0, (end_block - start_block + 1) * BYTES_PER_BLOCK);
#else
// zero out the additional bytes of the newly allocated blocks
// This is needed because the blocks may have previously held pointers
// to the heap and will not be set to something else if the caller
// doesn't actually use the entire block. As such they will continue
// to point to the heap and may prevent other blocks from being reclaimed.
memset((byte *)ret_ptr + n_bytes, 0, (end_block - start_block + 1) * BYTES_PER_BLOCK - n_bytes);
#endif
#if MICROPY_ENABLE_FINALISER
if (has_finaliser) {
// clear type pointer in case it is never set
((mp_obj_base_t *)ret_ptr)->type = NULL;
// set mp_obj flag only if it has a finaliser
GC_ENTER();
FTB_SET(start_block);
GC_EXIT();
}
#else
(void)has_finaliser;
#endif
#if EXTENSIVE_HEAP_PROFILING
gc_dump_alloc_table();
#endif
return ret_ptr;
}
/*
void *gc_alloc(mp_uint_t n_bytes) {
return _gc_alloc(n_bytes, false);
}
void *gc_alloc_with_finaliser(mp_uint_t n_bytes) {
return _gc_alloc(n_bytes, true);
}
*/
// force the freeing of a piece of memory
// TODO: freeing here does not call finaliser
void gc_free(void *ptr) {
if (MP_STATE_THREAD(gc_lock_depth) > 0) {
// TODO how to deal with this error?
return;
}
GC_ENTER();
DEBUG_printf("gc_free(%p)\n", ptr);
if (ptr == NULL) {
GC_EXIT();
} else {
// get the GC block number corresponding to this pointer
assert(VERIFY_PTR(ptr));
size_t block = BLOCK_FROM_PTR(ptr);
assert(ATB_GET_KIND(block) == AT_HEAD);
#if MICROPY_ENABLE_FINALISER
FTB_CLEAR(block);
#endif
// set the last_free pointer to this block if it's earlier in the heap
if (block / BLOCKS_PER_ATB < MP_STATE_MEM(gc_last_free_atb_index)) {
MP_STATE_MEM(gc_last_free_atb_index) = block / BLOCKS_PER_ATB;
}
// free head and all of its tail blocks
do {
ATB_ANY_TO_FREE(block);
block += 1;
} while (ATB_GET_KIND(block) == AT_TAIL);
GC_EXIT();
#if EXTENSIVE_HEAP_PROFILING
gc_dump_alloc_table();
#endif
}
}
size_t gc_nbytes(const void *ptr) {
GC_ENTER();
if (VERIFY_PTR(ptr)) {
size_t block = BLOCK_FROM_PTR(ptr);
if (ATB_GET_KIND(block) == AT_HEAD) {
// work out number of consecutive blocks in the chain starting with this on
size_t n_blocks = 0;
do {
n_blocks += 1;
} while (ATB_GET_KIND(block + n_blocks) == AT_TAIL);
GC_EXIT();
return n_blocks * BYTES_PER_BLOCK;
}
}
// invalid pointer
GC_EXIT();
return 0;
}
#if 0
// old, simple realloc that didn't expand memory in place
void *gc_realloc(void *ptr, mp_uint_t n_bytes) {
mp_uint_t n_existing = gc_nbytes(ptr);
if (n_bytes <= n_existing) {
return ptr;
} else {
bool has_finaliser;
if (ptr == NULL) {
has_finaliser = false;
} else {
#if MICROPY_ENABLE_FINALISER
has_finaliser = FTB_GET(BLOCK_FROM_PTR((mp_uint_t)ptr));
#else
has_finaliser = false;
#endif
}
void *ptr2 = gc_alloc(n_bytes, has_finaliser);
if (ptr2 == NULL) {
return ptr2;
}
memcpy(ptr2, ptr, n_existing);
gc_free(ptr);
return ptr2;
}
}
#else // Alternative gc_realloc impl
void *gc_realloc(void *ptr_in, size_t n_bytes, bool allow_move) {
// check for pure allocation
if (ptr_in == NULL) {
return gc_alloc(n_bytes, false);
}
// check for pure free
if (n_bytes == 0) {
gc_free(ptr_in);
return NULL;
}
if (MP_STATE_THREAD(gc_lock_depth) > 0) {
return NULL;
}
void *ptr = ptr_in;
GC_ENTER();
// get the GC block number corresponding to this pointer
assert(VERIFY_PTR(ptr));
size_t block = BLOCK_FROM_PTR(ptr);
assert(ATB_GET_KIND(block) == AT_HEAD);
// compute number of new blocks that are requested
size_t new_blocks = (n_bytes + BYTES_PER_BLOCK - 1) / BYTES_PER_BLOCK;
// Get the total number of consecutive blocks that are already allocated to
// this chunk of memory, and then count the number of free blocks following
// it. Stop if we reach the end of the heap, or if we find enough extra
// free blocks to satisfy the realloc. Note that we need to compute the
// total size of the existing memory chunk so we can correctly and
// efficiently shrink it (see below for shrinking code).
size_t n_free = 0;
size_t n_blocks = 1; // counting HEAD block
size_t max_block = MP_STATE_MEM(gc_alloc_table_byte_len) * BLOCKS_PER_ATB;
for (size_t bl = block + n_blocks; bl < max_block; bl++) {
byte block_type = ATB_GET_KIND(bl);
if (block_type == AT_TAIL) {
n_blocks++;
continue;
}
if (block_type == AT_FREE) {
n_free++;
if (n_blocks + n_free >= new_blocks) {
// stop as soon as we find enough blocks for n_bytes
break;
}
continue;
}
break;
}
// return original ptr if it already has the requested number of blocks
if (new_blocks == n_blocks) {
GC_EXIT();
return ptr_in;
}
// check if we can shrink the allocated area
if (new_blocks < n_blocks) {
// free unneeded tail blocks
for (size_t bl = block + new_blocks, count = n_blocks - new_blocks; count > 0; bl++, count--) {
ATB_ANY_TO_FREE(bl);
}
// set the last_free pointer to end of this block if it's earlier in the heap
if ((block + new_blocks) / BLOCKS_PER_ATB < MP_STATE_MEM(gc_last_free_atb_index)) {
MP_STATE_MEM(gc_last_free_atb_index) = (block + new_blocks) / BLOCKS_PER_ATB;
}
GC_EXIT();
#if EXTENSIVE_HEAP_PROFILING
gc_dump_alloc_table();
#endif
return ptr_in;
}
// check if we can expand in place
if (new_blocks <= n_blocks + n_free) {
// mark few more blocks as used tail
for (size_t bl = block + n_blocks; bl < block + new_blocks; bl++) {
assert(ATB_GET_KIND(bl) == AT_FREE);
ATB_FREE_TO_TAIL(bl);
}
GC_EXIT();
#if MICROPY_GC_CONSERVATIVE_CLEAR
// be conservative and zero out all the newly allocated blocks
memset((byte *)ptr_in + n_blocks * BYTES_PER_BLOCK, 0, (new_blocks - n_blocks) * BYTES_PER_BLOCK);
#else
// zero out the additional bytes of the newly allocated blocks (see comment above in gc_alloc)
memset((byte *)ptr_in + n_bytes, 0, new_blocks * BYTES_PER_BLOCK - n_bytes);
#endif
#if EXTENSIVE_HEAP_PROFILING
gc_dump_alloc_table();
#endif
return ptr_in;
}
#if MICROPY_ENABLE_FINALISER
bool ftb_state = FTB_GET(block);
#else
bool ftb_state = false;
#endif
GC_EXIT();
if (!allow_move) {
// not allowed to move memory block so return failure
return NULL;
}
// can't resize inplace; try to find a new contiguous chain
void *ptr_out = gc_alloc(n_bytes, ftb_state);
// check that the alloc succeeded
if (ptr_out == NULL) {
return NULL;
}
DEBUG_printf("gc_realloc(%p -> %p)\n", ptr_in, ptr_out);
memcpy(ptr_out, ptr_in, n_blocks * BYTES_PER_BLOCK);
gc_free(ptr_in);
return ptr_out;
}
#endif // Alternative gc_realloc impl
void gc_dump_info(void) {
gc_info_t info;
gc_info(&info);
mp_printf(&mp_plat_print, "GC: total: %u, used: %u, free: %u\n",
(uint)info.total, (uint)info.used, (uint)info.free);
mp_printf(&mp_plat_print, " No. of 1-blocks: %u, 2-blocks: %u, max blk sz: %u, max free sz: %u\n",
(uint)info.num_1block, (uint)info.num_2block, (uint)info.max_block, (uint)info.max_free);
}
void gc_dump_alloc_table(void) {
GC_ENTER();
static const size_t DUMP_BYTES_PER_LINE = 64;
#if !EXTENSIVE_HEAP_PROFILING
// When comparing heap output we don't want to print the starting
// pointer of the heap because it changes from run to run.
mp_printf(&mp_plat_print, "GC memory layout; from %p:", MP_STATE_MEM(gc_pool_start));
#endif
for (size_t bl = 0; bl < MP_STATE_MEM(gc_alloc_table_byte_len) * BLOCKS_PER_ATB; bl++) {
if (bl % DUMP_BYTES_PER_LINE == 0) {
// a new line of blocks
{
// check if this line contains only free blocks
size_t bl2 = bl;
while (bl2 < MP_STATE_MEM(gc_alloc_table_byte_len) * BLOCKS_PER_ATB && ATB_GET_KIND(bl2) == AT_FREE) {
bl2++;
}
if (bl2 - bl >= 2 * DUMP_BYTES_PER_LINE) {
// there are at least 2 lines containing only free blocks, so abbreviate their printing
mp_printf(&mp_plat_print, "\n (%u lines all free)", (uint)(bl2 - bl) / DUMP_BYTES_PER_LINE);
bl = bl2 & (~(DUMP_BYTES_PER_LINE - 1));
if (bl >= MP_STATE_MEM(gc_alloc_table_byte_len) * BLOCKS_PER_ATB) {
// got to end of heap
break;
}
}
}
// print header for new line of blocks
// (the cast to uint32_t is for 16-bit ports)
// mp_printf(&mp_plat_print, "\n%05x: ", (uint)(PTR_FROM_BLOCK(bl) & (uint32_t)0xfffff));
mp_printf(&mp_plat_print, "\n%05x: ", (uint)((bl * BYTES_PER_BLOCK) & (uint32_t)0xfffff));
}
int c = ' ';
switch (ATB_GET_KIND(bl)) {
case AT_FREE:
c = '.';
break;
/* this prints out if the object is reachable from BSS or STACK (for unix only)
case AT_HEAD: {
c = 'h';
void **ptrs = (void**)(void*)&mp_state_ctx;
mp_uint_t len = offsetof(mp_state_ctx_t, vm.stack_top) / sizeof(mp_uint_t);
for (mp_uint_t i = 0; i < len; i++) {
mp_uint_t ptr = (mp_uint_t)ptrs[i];
if (VERIFY_PTR(ptr) && BLOCK_FROM_PTR(ptr) == bl) {
c = 'B';
break;
}
}
if (c == 'h') {
ptrs = (void**)&c;
len = ((mp_uint_t)MP_STATE_THREAD(stack_top) - (mp_uint_t)&c) / sizeof(mp_uint_t);
for (mp_uint_t i = 0; i < len; i++) {
mp_uint_t ptr = (mp_uint_t)ptrs[i];
if (VERIFY_PTR(ptr) && BLOCK_FROM_PTR(ptr) == bl) {
c = 'S';
break;
}
}
}
break;
}
*/
/* this prints the uPy object type of the head block */
case AT_HEAD: {
void **ptr = (void **)(MP_STATE_MEM(gc_pool_start) + bl * BYTES_PER_BLOCK);
if (*ptr == &mp_type_tuple) {
c = 'T';
} else if (*ptr == &mp_type_list) {
c = 'L';
} else if (*ptr == &mp_type_dict) {
c = 'D';
} else if (*ptr == &mp_type_str || *ptr == &mp_type_bytes) {
c = 'S';
}
#if MICROPY_PY_BUILTINS_BYTEARRAY
else if (*ptr == &mp_type_bytearray) {
c = 'A';
}
#endif
#if MICROPY_PY_ARRAY
else if (*ptr == &mp_type_array) {
c = 'A';
}
#endif
#if MICROPY_PY_BUILTINS_FLOAT
else if (*ptr == &mp_type_float) {
c = 'F';
}
#endif
else if (*ptr == &mp_type_fun_bc) {
c = 'B';
} else if (*ptr == &mp_type_module) {
c = 'M';
} else {
c = 'h';
#if 0
// This code prints "Q" for qstr-pool data, and "q" for qstr-str
// data. It can be useful to see how qstrs are being allocated,
// but is disabled by default because it is very slow.
for (qstr_pool_t *pool = MP_STATE_VM(last_pool); c == 'h' && pool != NULL; pool = pool->prev) {
if ((qstr_pool_t *)ptr == pool) {
c = 'Q';
break;
}
for (const byte **q = pool->qstrs, **q_top = pool->qstrs + pool->len; q < q_top; q++) {
if ((const byte *)ptr == *q) {
c = 'q';
break;
}
}
}
#endif
}
break;
}
case AT_TAIL:
c = '=';
break;
case AT_MARK:
c = 'm';
break;
}
mp_printf(&mp_plat_print, "%c", c);
}
mp_print_str(&mp_plat_print, "\n");
GC_EXIT();
}
#if 0
// For testing the GC functions
void gc_test(void) {
mp_uint_t len = 500;
mp_uint_t *heap = malloc(len);
gc_init(heap, heap + len / sizeof(mp_uint_t));
void *ptrs[100];
{
mp_uint_t **p = gc_alloc(16, false);
p[0] = gc_alloc(64, false);
p[1] = gc_alloc(1, false);
p[2] = gc_alloc(1, false);
p[3] = gc_alloc(1, false);
mp_uint_t ***p2 = gc_alloc(16, false);
p2[0] = p;
p2[1] = p;
ptrs[0] = p2;
}
for (int i = 0; i < 25; i += 2) {
mp_uint_t *p = gc_alloc(i, false);
printf("p=%p\n", p);
if (i & 3) {
// ptrs[i] = p;
}
}
printf("Before GC:\n");
gc_dump_alloc_table();
printf("Starting GC...\n");
gc_collect_start();
gc_collect_root(ptrs, sizeof(ptrs) / sizeof(void *));
gc_collect_end();
printf("After GC:\n");
gc_dump_alloc_table();
}
#endif
#endif // MICROPY_ENABLE_GC
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