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dpgeorgedpgeorge
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py/gc: Execute finaliser code in a protected environment.
If a finaliser raises an exception then it must not propagate through the GC sweep function. This patch protects against such a thing by running finaliser code via the mp_call_function_1_protected call. This patch also adds scheduler lock/unlock calls around the finaliser execution to further protect against any possible reentrancy issues: the memory manager is already locked when doing a collection, but we also don't want to allow any scheduled code to run, KeyboardInterrupts to interupt the code, nor threads to switch.
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Lines changed: 8 additions & 6 deletions

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‎py/gc.c‎

Lines changed: 8 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -258,18 +258,20 @@ STATIC void gc_sweep(void) {
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case AT_HEAD:
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#if MICROPY_ENABLE_FINALISER
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if (FTB_GET(block)) {
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#if MICROPY_PY_THREAD
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// TODO need to think about reentrancy with finaliser code
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assert(!"finaliser with threading not implemented");
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#endif
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mp_obj_base_t *obj = (mp_obj_base_t*)PTR_FROM_BLOCK(block);
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if (obj->type != NULL) {
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// if the object has a type then see if it has a __del__ method
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mp_obj_t dest[2];
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mp_load_method_maybe(MP_OBJ_FROM_PTR(obj), MP_QSTR___del__, dest);
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if (dest[0] != MP_OBJ_NULL) {
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// load_method returned a method
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mp_call_method_n_kw(0, 0, dest);
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// load_method returned a method, execute it in a protected environment
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#if MICROPY_ENABLE_SCHEDULER
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mp_sched_lock();
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#endif
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mp_call_function_1_protected(dest[0], dest[1]);
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#if MICROPY_ENABLE_SCHEDULER
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mp_sched_unlock();
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#endif
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}
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}
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// clear finaliser flag

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