[patch] block/IDE/interrupt lockup

Andrew Morton (akpm@zip.com.au)
Fri, 29 Mar 2002 21:45:24 -0800


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() 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.

--- 2.4.19-pre5/drivers/block/ll_rw_blk.c~ide-lockup Fri Mar 29 21:19:11 2002
+++ 2.4.19-pre5-akpm/drivers/block/ll_rw_blk.c Fri Mar 29 21:20:04 2002
@@ -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)
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;

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