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openSUSE:Maintenance:7657
glibc.openSUSE_Leap_42.2_Update
malloc-Prevent-arena-free_list-from-turning-cyc...
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File malloc-Prevent-arena-free_list-from-turning-cyclic-B.patch of Package glibc.openSUSE_Leap_42.2_Update
2015-10-28 Florian Weimer <fweimer@redhat.com> [BZ# 19048] * malloc/malloc.c (struct malloc_state): Update comment. Add attached_threads member. (main_arena): Initialize attached_threads. * malloc/arena.c (list_lock): Update comment. (ptmalloc_lock_all, ptmalloc_unlock_all): Likewise. (ptmalloc_unlock_all2): Reinitialize arena reference counts. (deattach_arena): New function. (_int_new_arena): Initialize arena reference count and deattach replaced arena. (get_free_list, reused_arena): Update reference count and deattach replaced arena. (arena_thread_freeres): Update arena reference count and only put unreferenced arenas on the free list. Index: glibc-2.22/malloc/arena.c =================================================================== --- glibc-2.22.orig/malloc/arena.c +++ glibc-2.22/malloc/arena.c @@ -282,12 +282,19 @@ ptmalloc_unlock_all2 (void) tsd_setspecific (arena_key, save_arena); __malloc_hook = save_malloc_hook; __free_hook = save_free_hook; + + /* Push all arenas to the free list, except save_arena, which is + attached to the current thread. */ + if (save_arena != NULL) + ((mstate) save_arena)->attached_threads = 1; free_list = NULL; for (ar_ptr = &main_arena;; ) { mutex_init (&ar_ptr->mutex); if (ar_ptr != save_arena) { + /* This arena is no longer attached to any thread. */ + ar_ptr->attached_threads = 0; ar_ptr->next_free = free_list; free_list = ar_ptr; } @@ -727,6 +734,22 @@ heap_trim (heap_info *heap, size_t pad) /* Create a new arena with initial size "size". */ +/* If REPLACED_ARENA is not NULL, detach it from this thread. Must be + called while list_lock is held. */ +static void +detach_arena (mstate replaced_arena) +{ + if (replaced_arena != NULL) + { + assert (replaced_arena->attached_threads > 0); + /* The current implementation only detaches from main_arena in + case of allocation failure. This means that it is likely not + beneficial to put the arena on free_list even if the + reference count reaches zero. */ + --replaced_arena->attached_threads; + } +} + static mstate _int_new_arena (size_t size) { @@ -748,6 +771,7 @@ _int_new_arena (size_t size) } a = h->ar_ptr = (mstate) (h + 1); malloc_init_state (a); + a->attached_threads = 1; /*a->next = NULL;*/ a->system_mem = a->max_system_mem = h->size; arena_mem += h->size; @@ -761,12 +785,16 @@ _int_new_arena (size_t size) set_head (top (a), (((char *) h + h->size) - ptr) | PREV_INUSE); LIBC_PROBE (memory_arena_new, 2, a, size); + mstate replaced_arena; + arena_lookup (replaced_arena); tsd_setspecific (arena_key, (void *) a); mutex_init (&a->mutex); (void) mutex_lock (&a->mutex); (void) mutex_lock (&list_lock); + detach_arena (replaced_arena); + /* Add the new arena to the global list. */ a->next = main_arena.next; atomic_write_barrier (); @@ -781,13 +809,24 @@ _int_new_arena (size_t size) static mstate get_free_list (void) { + mstate replaced_arena; + arena_lookup (replaced_arena); mstate result = free_list; if (result != NULL) { (void) mutex_lock (&list_lock); result = free_list; if (result != NULL) - free_list = result->next_free; + { + free_list = result->next_free; + + /* Arenas on the free list are not attached to any thread. */ + assert (result->attached_threads == 0); + /* But the arena will now be attached to this thread. */ + result->attached_threads = 1; + + detach_arena (replaced_arena); + } (void) mutex_unlock (&list_lock); if (result != NULL) @@ -846,6 +885,15 @@ reused_arena (mstate avoid_arena) (void) mutex_lock (&result->mutex); out: + { + mstate replaced_arena; + arena_lookup (replaced_arena); + (void) mutex_lock (&list_lock); + detach_arena (replaced_arena); + ++result->attached_threads; + (void) mutex_unlock (&list_lock); + } + LIBC_PROBE (memory_arena_reuse, 2, result, avoid_arena); tsd_setspecific (arena_key, (void *) result); next_to_use = result->next; @@ -939,8 +987,14 @@ arena_thread_freeres (void) if (a != NULL) { (void) mutex_lock (&list_lock); - a->next_free = free_list; - free_list = a; + /* If this was the last attached thread for this arena, put the + arena on the free list. */ + assert (a->attached_threads > 0); + if (--a->attached_threads == 0) + { + a->next_free = free_list; + free_list = a; + } (void) mutex_unlock (&list_lock); } } Index: glibc-2.22/malloc/malloc.c =================================================================== --- glibc-2.22.orig/malloc/malloc.c +++ glibc-2.22/malloc/malloc.c @@ -1709,9 +1709,15 @@ struct malloc_state /* Linked list */ struct malloc_state *next; - /* Linked list for free arenas. */ + /* Linked list for free arenas. Access to this field is serialized + by 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. */ + INTERNAL_SIZE_T attached_threads; + /* Memory allocated from the system in this arena. */ INTERNAL_SIZE_T system_mem; INTERNAL_SIZE_T max_system_mem; @@ -1755,7 +1761,8 @@ struct malloc_par static struct malloc_state main_arena = { .mutex = MUTEX_INITIALIZER, - .next = &main_arena + .next = &main_arena, + .attached_threads = 1 }; /* There is only one instance of the malloc parameters. */
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