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authorVegard Nossum <vegard.nossum@gmail.com>2008-06-14 18:47:36 -0400
committerThomas Gleixner <tglx@linutronix.de>2008-06-18 05:09:54 -0400
commit50db04dd9c74178e68a981a7127c37252ffb3242 (patch)
treeac961b1ccc6f5073537be2b4b731bc79ec5448c4
parent952f4a0a9b27e6dbd5d32e330b3f609ebfa0b061 (diff)
debugobjects: fix lockdep warning
Daniel J Blueman reported: | ======================================================= | [ INFO: possible circular locking dependency detected ] | 2.6.26-rc5-201c #1 | ------------------------------------------------------- | nscd/3669 is trying to acquire lock: | (&n->list_lock){.+..}, at: [<ffffffff802bab03>] deactivate_slab+0x173/0x1e0 | | but task is already holding lock: | (&obj_hash[i].lock){++..}, at: [<ffffffff803fa56f>] | __debug_object_init+0x2f/0x350 | | which lock already depends on the new lock. There are two locks involved here; the first is a SLUB-local lock, and the second is a debugobjects-local lock. They are basically taken in two different orders: 1. SLUB { debugobjects { ... } } 2. debugobjects { SLUB { ... } } This patch changes pattern #2 by trying to fill the memory pool (e.g. the call into SLUB/kmalloc()) outside the debugobjects lock, so now the two patterns look like this: 1. SLUB { debugobjects { ... } } 2. SLUB { } debugobjects { ... } [ daniel.blueman@gmail.com: pool_lock needs to be taken irq safe in fill_pool ] Reported-by: Daniel J Blueman <daniel.blueman@gmail.com> Signed-off-by: Vegard Nossum <vegard.nossum@gmail.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
-rw-r--r--lib/debugobjects.c15
1 files changed, 6 insertions, 9 deletions
diff --git a/lib/debugobjects.c b/lib/debugobjects.c
index a76a5e122ae1..85b18d79be89 100644
--- a/lib/debugobjects.c
+++ b/lib/debugobjects.c
@@ -68,6 +68,7 @@ static int fill_pool(void)
68{ 68{
69 gfp_t gfp = GFP_ATOMIC | __GFP_NORETRY | __GFP_NOWARN; 69 gfp_t gfp = GFP_ATOMIC | __GFP_NORETRY | __GFP_NOWARN;
70 struct debug_obj *new; 70 struct debug_obj *new;
71 unsigned long flags;
71 72
72 if (likely(obj_pool_free >= ODEBUG_POOL_MIN_LEVEL)) 73 if (likely(obj_pool_free >= ODEBUG_POOL_MIN_LEVEL))
73 return obj_pool_free; 74 return obj_pool_free;
@@ -81,10 +82,10 @@ static int fill_pool(void)
81 if (!new) 82 if (!new)
82 return obj_pool_free; 83 return obj_pool_free;
83 84
84 spin_lock(&pool_lock); 85 spin_lock_irqsave(&pool_lock, flags);
85 hlist_add_head(&new->node, &obj_pool); 86 hlist_add_head(&new->node, &obj_pool);
86 obj_pool_free++; 87 obj_pool_free++;
87 spin_unlock(&pool_lock); 88 spin_unlock_irqrestore(&pool_lock, flags);
88 } 89 }
89 return obj_pool_free; 90 return obj_pool_free;
90} 91}
@@ -110,16 +111,13 @@ static struct debug_obj *lookup_object(void *addr, struct debug_bucket *b)
110} 111}
111 112
112/* 113/*
113 * Allocate a new object. If the pool is empty and no refill possible, 114 * Allocate a new object. If the pool is empty, switch off the debugger.
114 * switch off the debugger.
115 */ 115 */
116static struct debug_obj * 116static struct debug_obj *
117alloc_object(void *addr, struct debug_bucket *b, struct debug_obj_descr *descr) 117alloc_object(void *addr, struct debug_bucket *b, struct debug_obj_descr *descr)
118{ 118{
119 struct debug_obj *obj = NULL; 119 struct debug_obj *obj = NULL;
120 int retry = 0;
121 120
122repeat:
123 spin_lock(&pool_lock); 121 spin_lock(&pool_lock);
124 if (obj_pool.first) { 122 if (obj_pool.first) {
125 obj = hlist_entry(obj_pool.first, typeof(*obj), node); 123 obj = hlist_entry(obj_pool.first, typeof(*obj), node);
@@ -141,9 +139,6 @@ repeat:
141 } 139 }
142 spin_unlock(&pool_lock); 140 spin_unlock(&pool_lock);
143 141
144 if (fill_pool() && !obj && !retry++)
145 goto repeat;
146
147 return obj; 142 return obj;
148} 143}
149 144
@@ -261,6 +256,8 @@ __debug_object_init(void *addr, struct debug_obj_descr *descr, int onstack)
261 struct debug_obj *obj; 256 struct debug_obj *obj;
262 unsigned long flags; 257 unsigned long flags;
263 258
259 fill_pool();
260
264 db = get_bucket((unsigned long) addr); 261 db = get_bucket((unsigned long) addr);
265 262
266 spin_lock_irqsave(&db->lock, flags); 263 spin_lock_irqsave(&db->lock, flags);