remove vestigal locking from obmalloc (GH-5805)

obmalloc has (empty) macros for locking in the allocator. These aren't needed in CPython; we rely on the GIL.

Objects/obmalloc.c

@@ -849,30 +849,6 @@ static int running_on_valgrind = -1;
 
 /*==========================================================================*/
 
-/*
- * Locking
- *
- * To reduce lock contention, it would probably be better to refine the
- * crude function locking with per size class locking. I'm not positive
- * however, whether it's worth switching to such locking policy because
- * of the performance penalty it might introduce.
- *
- * The following macros describe the simplest (should also be the fastest)
- * lock object on a particular platform and the init/fini/lock/unlock
- * operations on it. The locks defined here are not expected to be recursive
- * because it is assumed that they will always be called in the order:
- * INIT, [LOCK, UNLOCK]*, FINI.
- */
-
-/*
- * Python's threads are serialized, so object malloc locking is disabled.
- */
-#define SIMPLELOCK_DECL(lock)   /* simple lock declaration              */
-#define SIMPLELOCK_INIT(lock)   /* allocate (if needed) and initialize  */
-#define SIMPLELOCK_FINI(lock)   /* free/destroy an existing lock        */
-#define SIMPLELOCK_LOCK(lock)   /* acquire released lock */
-#define SIMPLELOCK_UNLOCK(lock) /* release acquired lock */
-
 /* When you say memory, my mind reasons in terms of (pointers to) blocks */
 typedef uint8_t block;
 
@@ -944,15 +920,6 @@ struct arena_object {
 
 /*==========================================================================*/
 
-/*
- * This malloc lock
- */
-SIMPLELOCK_DECL(_malloc_lock)
-#define LOCK()          SIMPLELOCK_LOCK(_malloc_lock)
-#define UNLOCK()        SIMPLELOCK_UNLOCK(_malloc_lock)
-#define LOCK_INIT()     SIMPLELOCK_INIT(_malloc_lock)
-#define LOCK_FINI()     SIMPLELOCK_FINI(_malloc_lock)
-
 /*
  * Pool table -- headed, circular, doubly-linked lists of partially used pools.
 
@@ -1381,7 +1348,6 @@ pymalloc_alloc(void *ctx, void **ptr_p, size_t nbytes)
         return 0;
     }
 
-    LOCK();
     /*
      * Most frequent paths first
      */
@@ -1537,13 +1503,11 @@ pymalloc_alloc(void *ctx, void **ptr_p, size_t nbytes)
     goto init_pool;
 
 success:
-    UNLOCK();
     assert(bp != NULL);
     *ptr_p = (void *)bp;
     return 1;
 
 failed:
-    UNLOCK();
     return 0;
 }
 
@@ -1612,8 +1576,6 @@ pymalloc_free(void *ctx, void *p)
     }
     /* We allocated this address. */
 
-    LOCK();
-
     /* Link p to the start of the pool's freeblock list.  Since
      * the pool had at least the p block outstanding, the pool
      * wasn't empty (so it's already in a usedpools[] list, or
@@ -1798,7 +1760,6 @@ pymalloc_free(void *ctx, void *p)
     goto success;
 
 success:
-    UNLOCK();
     return 1;
 }