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py/map: Make map rehashing an atomic operation. #11604

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e77e99b
py/map: Make map rehashing an atomic operation.
dpgeorge May 24, 2023
d5a023b
tests/thread: Add a test to stress concurrent globals access.
dpgeorge Feb 20, 2024
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25 changes: 19 additions & 6 deletions py/map.c
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Original file line number Diff line number Diff line change
Expand Up @@ -32,6 +32,7 @@
#include "py/mpconfig.h"
#include "py/misc.h"
#include "py/runtime.h"
#include "py/mphal.h"

#if MICROPY_DEBUG_VERBOSE // print debugging info
#define DEBUG_PRINT (1)
Expand Down Expand Up @@ -134,16 +135,28 @@ STATIC void mp_map_rehash(mp_map_t *map) {
DEBUG_printf("mp_map_rehash(%p): " UINT_FMT " -> " UINT_FMT "\n", map, old_alloc, new_alloc);
mp_map_elem_t *old_table = map->table;
mp_map_elem_t *new_table = m_new0(mp_map_elem_t, new_alloc);
// If we reach this point, table resizing succeeded, now we can edit the old map.
map->alloc = new_alloc;
map->used = 0;
map->all_keys_are_qstrs = 1;
map->table = new_table;

// If we reach this point then allocating the new table succeeded, so construct the new map.
mp_map_t new_map = {
.all_keys_are_qstrs = 1,
.is_fixed = 0,
.is_ordered = 0,
.used = 0,
.alloc = new_alloc,
.table = new_table,
};
for (size_t i = 0; i < old_alloc; i++) {
if (old_table[i].key != MP_OBJ_NULL && old_table[i].key != MP_OBJ_SENTINEL) {
mp_map_lookup(map, old_table[i].key, MP_MAP_LOOKUP_ADD_IF_NOT_FOUND)->value = old_table[i].value;
mp_map_lookup(&new_map, old_table[i].key, MP_MAP_LOOKUP_ADD_IF_NOT_FOUND)->value = old_table[i].value;
}
}

// Swap the old map for the new one.
mp_uint_t atomic_state = MICROPY_BEGIN_ATOMIC_SECTION();
*map = new_map;
MICROPY_END_ATOMIC_SECTION(atomic_state);

// Free the old table.
m_del(mp_map_elem_t, old_table, old_alloc);
}

Expand Down
79 changes: 79 additions & 0 deletions tests/thread/stress_globals.py
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Original file line number Diff line number Diff line change
@@ -0,0 +1,79 @@
import time, _thread


def thread_task():
for _ in range(1000):
a00
print("pass")


print("start")
a00 = None

_thread.start_new_thread(thread_task, ())

# create lots of global variables
a01 = None
a02 = None
a03 = None
a04 = None
a05 = None
a06 = None
a07 = None
a10 = None
a11 = None
a12 = None
a13 = None
a14 = None
a15 = None
a16 = None
a17 = None
a18 = None
a19 = None
a20 = None
a21 = None
a22 = None
a23 = None
a24 = None
a25 = None
a26 = None
a27 = None
a28 = None
a29 = None
a30 = None
a31 = None
a32 = None
a33 = None
a34 = None
a35 = None
a36 = None
a37 = None
a38 = None
a39 = None
a40 = None
a41 = None
a42 = None
a43 = None
a44 = None
a45 = None
a46 = None
a47 = None
a48 = None
a49 = None
a50 = None
a51 = None
a52 = None
a53 = None
a54 = None
a55 = None
a56 = None
a57 = None
a58 = None
a59 = None
a60 = None
a61 = None
a62 = None
a63 = None

# let the thread finish
time.sleep(0.1)