block/IDE/interrupt lockup

PATCH New Andrew Morton 1 participant 1 message Mar 30, 2002 Block layer

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Andrew Morton

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2002-03-30 05:47 UTC #0 lore raw

PATCH 1/1 block/IDE/interrupt lockup

Marcelo,

my blk_grow_request_list() patch in -pre5 is buggy. It can cause boot-time lockups. The window is fairly small, but I just hit it.

drivers/ide/ide-probe.c:init_irq() does cli().
It calls down to blk_init_free_list() and
blk_grow_request_list().

blk_grow_request_list() does spin_unlock_irq(). Which is illegal inside cli(). An interrupt comes in and the CPU locks up in irq_enter(), spinning on global_irq_lock, which this CPU already holds.

Below is the patch. (That's the last spin_lock_irq() anyone will be seeing from me :))

Andre, init_irq() is somewhat broken - it appears to be assuming that cli() will disable interrupts, but it's
calling functions which can sleep. If these functions
_do_ sleep, interrupts will be enabled, which is presumably not what IDE wants to happen.

drivers/block/ll_rw_blk.c renamed from drivers/block/ll_rw_blk.c~ide-lockup +6 -4

@@ -336,14 +336,16 @@ void generic_unplug_device(void *data)
  */
 int blk_grow_request_list(request_queue_t *q, int nr_requests)
 {
-	spin_lock_irq(&io_request_lock);
+	unsigned long flags;
+
+	spin_lock_irqsave(&io_request_lock, flags);
 	while (q->nr_requests < nr_requests) {
 		struct request *rq;
 		int rw;
 
-		spin_unlock_irq(&io_request_lock);
+		spin_unlock_irqrestore(&io_request_lock, flags);
 		rq = kmem_cache_alloc(request_cachep, SLAB_KERNEL);
-		spin_lock_irq(&io_request_lock);
+		spin_lock_irqsave(&io_request_lock, flags);
 		if (rq == NULL)
 			break;
 		memset(rq, 0, sizeof(*rq));

@@ -356,7 +358,7 @@ int blk_grow_request_list(request_queue_
 	q->batch_requests = q->nr_requests / 4;
 	if (q->batch_requests > 32)
 		q->batch_requests = 32;
-	spin_unlock_irq(&io_request_lock);
+	spin_unlock_irqrestore(&io_request_lock, flags);
 	return q->nr_requests;
 }