IB/mthca: Use IRQ safe locks to protect allocation bitmaps

It is supposed to be OK to call mthca_create_ah() and mthca_destroy_ah() from any context. However, for mem-full HCAs, these functions use the mthca_alloc() and mthca_free() bitmap helpers, and those helpers use non-IRQ-safe spin_lock() internally. Lockdep correctly warns that this could lead to a deadlock. Fix this by changing mthca_alloc() and mthca_free() to use spin_lock_irqsave(). Signed-off-by: Roland Dreier <rolandd@cisco.com>

IB/mthca: Use IRQ safe locks to protect allocation bitmaps
It is supposed to be OK to call mthca_create_ah() and mthca_destroy_ah() from any context. However, for mem-full HCAs, these functions use the mthca_alloc() and mthca_free() bitmap helpers, and those helpers use non-IRQ-safe spin_lock() internally. Lockdep correctly warns that this could lead to a deadlock. Fix this by changing mthca_alloc() and mthca_free() to use spin_lock_irqsave(). Signed-off-by: Roland Dreier <rolandd@cisco.com>
Roland Dreier
1 parent 22db37ec5f
Showing 1 changed file with 11 additions and 4 deletions Side-by-side Diff
drivers/infiniband/hw/mthca/mthca_allocator.c
@@ -41,9 +41,11 @@
 /* Trivial bitmap-based allocator */
 u32 mthca_alloc(struct mthca_alloc *alloc)
 {
+	unsigned long flags;
 	u32 obj;
  
-	spin_lock(&alloc->lock);
+	spin_lock_irqsave(&alloc->lock, flags);
+
 	obj = find_next_zero_bit(alloc->table, alloc->max, alloc->last);
 	if (obj >= alloc->max) {
 		alloc->top = (alloc->top + alloc->max) & alloc->mask;
  
  
  
@@ -56,19 +58,24 @@
 	} else
 		obj = -1;
  
-	spin_unlock(&alloc->lock);
+	spin_unlock_irqrestore(&alloc->lock, flags);
  
 	return obj;
 }
  
 void mthca_free(struct mthca_alloc *alloc, u32 obj)
 {
+	unsigned long flags;
+
 	obj &= alloc->max - 1;
-	spin_lock(&alloc->lock);
+
+	spin_lock_irqsave(&alloc->lock, flags);
+
 	clear_bit(obj, alloc->table);
 	alloc->last = min(alloc->last, obj);
 	alloc->top = (alloc->top + alloc->max) & alloc->mask;
-	spin_unlock(&alloc->lock);
+
+	spin_unlock_irqrestore(&alloc->lock, flags);
 }
  
 int mthca_alloc_init(struct mthca_alloc *alloc, u32 num, u32 mask,
...	...	@@ -41,9 +41,11 @@
41	41	/* Trivial bitmap-based allocator */
42	42	u32 mthca_alloc(struct mthca_alloc *alloc)
43	43	{
	44	+ unsigned long flags;
44	45	u32 obj;
45	46
46		- spin_lock(&alloc->lock);
	47	+ spin_lock_irqsave(&alloc->lock, flags);
	48	+
47	49	obj = find_next_zero_bit(alloc->table, alloc->max, alloc->last);
48	50	if (obj >= alloc->max) {
49	51	alloc->top = (alloc->top + alloc->max) & alloc->mask;
50	52
51	53
52	54
...	...	@@ -56,19 +58,24 @@
56	58	} else
57	59	obj = -1;
58	60
59		- spin_unlock(&alloc->lock);
	61	+ spin_unlock_irqrestore(&alloc->lock, flags);
60	62
61	63	return obj;
62	64	}
63	65
64	66	void mthca_free(struct mthca_alloc *alloc, u32 obj)
65	67	{
	68	+ unsigned long flags;
	69	+
66	70	obj &= alloc->max - 1;
67		- spin_lock(&alloc->lock);
	71	+
	72	+ spin_lock_irqsave(&alloc->lock, flags);
	73	+
68	74	clear_bit(obj, alloc->table);
69	75	alloc->last = min(alloc->last, obj);
70	76	alloc->top = (alloc->top + alloc->max) & alloc->mask;
71		- spin_unlock(&alloc->lock);
	77	+
	78	+ spin_unlock_irqrestore(&alloc->lock, flags);
72	79	}
73	80
74	81	int mthca_alloc_init(struct mthca_alloc *alloc, u32 num, u32 mask,