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Code Activity

malloc: Fix list_lock/arena lock deadlock [BZ #19182]

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* malloc/arena.c (list_lock): Document lock ordering requirements.
	(free_list_lock): New lock.
	(ptmalloc_lock_all): Comment on free_list_lock.
	(ptmalloc_unlock_all2): Reinitialize free_list_lock.
	(detach_arena): Update comment.  free_list_lock is now needed.
	(_int_new_arena): Use free_list_lock around detach_arena call.
	Acquire arena lock after list_lock.  Add comment, including FIXME
	about incorrect synchronization.
	(get_free_list): Switch to free_list_lock.
	(reused_arena): Acquire free_list_lock around detach_arena call
	and attached threads counter update.  Add two FIXMEs about
	incorrect synchronization.
	(arena_thread_freeres): Switch to free_list_lock.
	* malloc/malloc.c (struct malloc_state): Update comments to
	mention free_list_lock.
This commit is contained in:
Florian Weimer
2015-12-21 16:42:46 +01:00
parent b300455644
commit 90c400bd49
3 changed files with 73 additions and 18 deletions
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6
malloc/malloc.c
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@ -1710,12 +1710,12 @@ struct malloc_state
struct malloc_state *next;
/* Linked list for free arenas. Access to this field is serialized
by list_lock in arena.c. */
by free_list_lock in arena.c. */
struct malloc_state *next_free;
/* Number of threads attached to this arena. 0 if the arena is on
the free list. Access to this field is serialized by list_lock
in arena.c. */
the free list. Access to this field is serialized by
free_list_lock in arena.c. */
INTERNAL_SIZE_T attached_threads;
/* Memory allocated from the system in this arena. */