From fa476d01f1c1990a92ee49d1f1c557b83805d0e9 Mon Sep 17 00:00:00 2001 From: Freeman Wang Date: Sat, 19 Dec 2009 13:43:00 -0800 Subject: [PATCH 8/9] malloc: fix race condition and other bugs in the no-mmu malloc Fixes multiple race conditions on mmb list. This was done by making the mmb_heap_lock into a recursive lock and making the regular heap_lock extend to cover the mmb heap handling. Also move the new_mmb allocation up to before the mmb list is iterated through to find the insertion point. When the mmb_heap also runs out and needs to be extended when the regular heap is just extended, the mmb list could be messed up. Signed-off-by: Freeman Wang Signed-off-by: Austin Foxley --- libc/stdlib/malloc/free.c | 6 +++--- libc/stdlib/malloc/malloc.c | 7 ++++--- 2 files changed, 7 insertions(+), 6 deletions(-) diff --git a/libc/stdlib/malloc/free.c b/libc/stdlib/malloc/free.c index 90e18f4..741248a 100644 --- a/libc/stdlib/malloc/free.c +++ b/libc/stdlib/malloc/free.c @@ -179,14 +179,14 @@ __free_to_heap (void *mem, struct heap_free_area **heap /* Start searching again from the end of this block. */ start = mmb_end; + /* Release the descriptor block we used. */ + free_to_heap (mmb, &__malloc_mmb_heap, &__malloc_mmb_heap_lock); + /* We have to unlock the heap before we recurse to free the mmb descriptor, because we might be unmapping from the mmb heap. */ __heap_unlock (heap_lock); - /* Release the descriptor block we used. */ - free_to_heap (mmb, &__malloc_mmb_heap, &__malloc_mmb_heap_lock); - /* Do the actual munmap. */ munmap ((void *)mmb_start, mmb_end - mmb_start); diff --git a/libc/stdlib/malloc/malloc.c b/libc/stdlib/malloc/malloc.c index 71f9e58..84a6acd 100644 --- a/libc/stdlib/malloc/malloc.c +++ b/libc/stdlib/malloc/malloc.c @@ -48,7 +48,7 @@ struct malloc_mmb *__malloc_mmapped_blocks = 0; HEAP_DECLARE_STATIC_FREE_AREA (initial_mmb_fa, 48); /* enough for 3 mmbs */ struct heap_free_area *__malloc_mmb_heap = HEAP_INIT_WITH_FA (initial_mmb_fa); #ifdef HEAP_USE_LOCKING -pthread_mutex_t __malloc_mmb_heap_lock = PTHREAD_MUTEX_INITIALIZER; +pthread_mutex_t __malloc_mmb_heap_lock = PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP; #endif #endif /* __UCLIBC_UCLINUX_BROKEN_MUNMAP__ */ @@ -151,19 +151,19 @@ __malloc_from_heap (size_t size, struct heap_free_area **heap /* Try again to allocate. */ mem = __heap_alloc (heap, &size); - __heap_unlock (heap_lock); #if !defined(MALLOC_USE_SBRK) && defined(__UCLIBC_UCLINUX_BROKEN_MUNMAP__) /* Insert a record of BLOCK in sorted order into the __malloc_mmapped_blocks list. */ + new_mmb = malloc_from_heap (sizeof *new_mmb, &__malloc_mmb_heap, &__malloc_mmb_heap_lock); + for (prev_mmb = 0, mmb = __malloc_mmapped_blocks; mmb; prev_mmb = mmb, mmb = mmb->next) if (block < mmb->mem) break; - new_mmb = malloc_from_heap (sizeof *new_mmb, &__malloc_mmb_heap, &__malloc_mmb_heap_lock); new_mmb->next = mmb; new_mmb->mem = block; new_mmb->size = block_size; @@ -177,6 +177,7 @@ __malloc_from_heap (size_t size, struct heap_free_area **heap (unsigned)new_mmb, (unsigned)new_mmb->mem, block_size); #endif /* !MALLOC_USE_SBRK && __UCLIBC_UCLINUX_BROKEN_MUNMAP__ */ + __heap_unlock (heap_lock); } } -- 1.6.6.1