gh-112532: Isolate abandoned segments by interpreter (#113717)

* gh-112532: Isolate abandoned segments by interpreter

Mimalloc segments are data structures that contain memory allocations along
with metadata. Each segment is "owned" by a thread. When a thread exits,
it abandons its segments to a global pool to be later reclaimed by other
threads. This changes the pool to be per-interpreter instead of process-wide.

This will be important for when we use mimalloc to find GC objects in the
`--disable-gil` builds. We want heaps to only store Python objects from a
single interpreter. Absent this change, the abandoning and reclaiming process
could break this isolation.

* Add missing '&_mi_abandoned_default' to 'tld_empty'

1 files changed, 6 insertions, 0 deletions

diff --git a/Include/internal/pycore_mimalloc.h b/Include/internal/pycore_mimalloc.h
index adebb55..1e7ed5a 100644
--- a/Include/internal/pycore_mimalloc.h
+++ b/Include/internal/pycore_mimalloc.h
@@ -35,6 +35,12 @@ typedef enum {
 #endif
 
 #ifdef Py_GIL_DISABLED
+struct _mimalloc_interp_state {
+    // When exiting, threads place any segments with live blocks in this
+    // shared pool for other threads to claim and reuse.
+    mi_abandoned_pool_t abandoned_pool;
+};
+
 struct _mimalloc_thread_state {
     mi_heap_t *current_object_heap;
     mi_heap_t heaps[_Py_MIMALLOC_HEAP_COUNT];