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xen-devel
[Xen-devel] Re: WARNING: at kernel/timer.c:1012 del_timer_sync+0x39/0x4e
On 2011-03-25 13:28, Jeremy Fitzhardinge wrote:
> In today's linux-2.6.38+ I'm seeing this in my Xen domains:
>
> ------------[ cut here ]------------
> WARNING: at /home/jeremy/git/upstream/kernel/timer.c:1012
> del_timer_sync+0x39/0x4e()
> Modules linked in: sunrpc microcode [last unloaded: scsi_wait_scan]
> Pid: 0, comm: swapper Tainted: G W 2.6.38+ #349
> Call Trace:
> <IRQ> [<ffffffff8104c283>] ? del_timer_sync+0x39/0x4e
> [<ffffffff8103f080>] warn_slowpath_common+0x85/0x9d
> [<ffffffff8103f0b2>] warn_slowpath_null+0x1a/0x1c
> [<ffffffff8104c283>] del_timer_sync+0x39/0x4e
> [<ffffffff81206d4e>] blk_stop_queue+0x1d/0x6d
> [<ffffffff812e82f6>] do_blkif_request+0x35d/0x3ba
> [<ffffffff8120560f>] __blk_run_queue+0x7d/0xd7
> [<ffffffff81205880>] blk_start_queue+0x78/0x7d
> [<ffffffff812e837b>] kick_pending_request_queues+0x28/0x38
> [<ffffffff812e85d5>] blkif_interrupt+0x1f8/0x21c
> [<ffffffff8108e866>] handle_irq_event_percpu+0x61/0x1a5
> [<ffffffff8108e9fa>] handle_irq_event+0x50/0x74
> [<ffffffff81090c87>] handle_fasteoi_irq+0x7e/0xaa
> [<ffffffff812853aa>] __xen_evtchn_do_upcall+0x166/0x206
> [<ffffffff81286d32>] xen_evtchn_do_upcall+0x2f/0x42
> [<ffffffff8150148e>] xen_do_hypervisor_callback+0x1e/0x30
> <EOI> [<ffffffff810013aa>] ? hypercall_page+0x3aa/0x1000
> [<ffffffff810013aa>] ? hypercall_page+0x3aa/0x1000
> [<ffffffff81006c34>] ? xen_safe_halt+0x10/0x18
> [<ffffffff81010251>] ? default_idle+0x6a/0xc3
> [<ffffffff810091af>] ? cpu_idle+0x6b/0x8a
> [<ffffffff814e1b2e>] ? rest_init+0x72/0x74
> [<ffffffff81b04b70>] ? start_kernel+0x39b/0x3a6
> [<ffffffff81b042cb>] ? x86_64_start_reservations+0xb6/0xba
> [<ffffffff81b07d6f>] ? xen_start_kernel+0x5dc/0x5e3
> ---[ end trace 1605d7ec4cdfe9eb ]---
>
> Which is the result of this call to blk_stop_queue() in
> drivers/block/xen-blkfront.c:
>
> static void do_blkif_request(struct request_queue *rq)
> {
> [...]
> if (blkif_queue_request(req)) {
> blk_requeue_request(rq, req);
> wait:
> /* Avoid pointless unplugs. */
> blk_stop_queue(rq);
> break;
> }
>
>
>
> How should this be fixed? Is this call to blk_stop_queue() bogus, or is
> it OK to call it in a handler like this? If so, is the warning itself
> wrong?
Calling it in there should be fine, the problem is that the work cancel
turns into a sync timer delete. That is not needed. Can you try the
below?
> Does this relate to 7eaceaccab5f4 "block: remove per-queue plugging"?
No
diff --git a/block/blk-core.c b/block/blk-core.c
index 59b5c00..f97c088 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -271,7 +271,7 @@ EXPORT_SYMBOL(blk_start_queue);
**/
void blk_stop_queue(struct request_queue *q)
{
- cancel_delayed_work(&q->delay_work);
+ __cancel_delayed_work(&q->delay_work);
queue_flag_set(QUEUE_FLAG_STOPPED, q);
}
EXPORT_SYMBOL(blk_stop_queue);
--
Jens Axboe
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