Avoid that I/O completion processing triggers the following complaints
if kernel debug options that slow down the kernel significantly are
enabled:
NMI watchdog: BUG: soft lockup - CPU#3 stuck for 22s! [kdmwork-254:2:358]
irq event stamp: 15233868
hardirqs last enabled at (15233867): [<ffffffff81578167>] _raw_spin_unlock_irq+0x27/0x40
hardirqs last disabled at (15233868): [<ffffffff81579664>] apic_timer_interrupt+0x84/0x90
softirqs last enabled at (15233850): [<ffffffff8105a55b>] __do_softirq+0x1cb/0x230
softirqs last disabled at (15233743): [<ffffffff8105a748>] irq_exit+0xa8/0xb0
CPU: 3 PID: 358 Comm: kdmwork-254:2
RIP: 0010:[<ffffffff8157816f>] [<ffffffff8157816f>] _raw_spin_unlock_irq+0x2f/0x40
Call Trace:
[<ffffffff813dbe28>] scsi_request_fn+0x118/0x600
[<ffffffff8128190e>] __blk_run_queue+0x2e/0x40
[<ffffffff81281175>] __elv_add_request+0x75/0x1f0
[<ffffffff81285b11>] blk_insert_cloned_request+0x101/0x190
[<ffffffffa0170eee>] map_request+0x18e/0x210 [dm_mod]
[<ffffffffa0170f8d>] map_tio_request+0x1d/0x40 [dm_mod]
[<ffffffff81075a0d>] kthread_worker_fn+0x7d/0x1a0
[<ffffffff8107591a>] kthread+0xea/0x100
[<ffffffff81578c7f>] ret_from_fork+0x3f/0x70
INFO: rcu_sched self-detected stall on CPU
3-...: (6497 ticks this GP) idle=fb9/140000000000002/0 softirq=2044956/2045037 fqs=5414
(t=6500 jiffies g=219289 c=219288 q=7233211)
Task dump for CPU 3:
kdmwork-254:2 R running task 0 358 2 0x00000008
Call Trace:
<IRQ> [<ffffffff8108195f>] sched_show_task+0xbf/0x150
[<ffffffff81084742>] dump_cpu_task+0x32/0x40
[<ffffffff810b5e79>] rcu_dump_cpu_stacks+0x89/0xe0
[<ffffffff810b9999>] rcu_check_callbacks+0x439/0x730
[<ffffffff810bc1c4>] update_process_times+0x34/0x60
[<ffffffff810caaa0>] tick_sched_handle.isra.18+0x20/0x50
[<ffffffff810cb148>] tick_sched_timer+0x38/0x70
[<ffffffff810bc865>] __hrtimer_run_queues+0xa5/0x1c0
[<ffffffff810bcef6>] hrtimer_interrupt+0xa6/0x1b0
[<ffffffff81038ba3>] smp_trace_apic_timer_interrupt+0x63/0x90
[<ffffffff81038bd9>] smp_apic_timer_interrupt+0x9/0x10
[<ffffffff81579669>] apic_timer_interrupt+0x89/0x90
[<ffffffff811640d6>] __slab_free+0xc6/0x270
[<ffffffff811643d9>] kmem_cache_free+0x159/0x160
[<ffffffff811d0a12>] kiocb_free+0x32/0x40
[<ffffffff811d1b75>] aio_complete+0x1e5/0x3c0
[<ffffffff811bef45>] dio_complete+0x75/0x1d0
[<ffffffff811bf11a>] dio_bio_end_aio+0x7a/0x130
[<ffffffff812800da>] bio_endio+0x3a/0x60
[<ffffffff81284b7c>] blk_update_request+0x7c/0x2a0
[<ffffffffa016fcc1>] end_clone_bio+0x41/0x70 [dm_mod]
[<ffffffff812800da>] bio_endio+0x3a/0x60
[<ffffffff81284b7c>] blk_update_request+0x7c/0x2a0
[<ffffffff813da01e>] scsi_end_request+0x2e/0x1d0
[<ffffffff813dc444>] scsi_io_completion+0xb4/0x610
[<ffffffff813d3e0a>] scsi_finish_command+0xca/0x120
[<ffffffff813dbcf0>] scsi_softirq_done+0x120/0x140
[<ffffffff8128c742>] blk_done_softirq+0x72/0x90
[<ffffffff8105a49f>] __do_softirq+0x10f/0x230
[<ffffffff8105a748>] irq_exit+0xa8/0xb0
[<ffffffff810065a5>] do_IRQ+0x65/0x110
[<ffffffff815793c9>] common_interrupt+0x89/0x89
<EOI>
[<ffffffffa010f815>] __multipath_map.isra.16+0x145/0x260 [dm_multipath]
[<ffffffffa010f962>] multipath_map+0x12/0x20 [dm_multipath]
[<ffffffffa0170da3>] map_request+0x43/0x210 [dm_mod]
[<ffffffffa0170f8d>] map_tio_request+0x1d/0x40 [dm_mod]
[<ffffffff81075a0d>] kthread_worker_fn+0x7d/0x1a0
[<ffffffff8107591a>] kthread+0xea/0x100
[<ffffffff81578c7f>] ret_from_fork+0x3f/0x70
Signed-off-by: Bart Van Assche <bart.vanassche@xxxxxxxxxxx>
---
drivers/scsi/scsi_lib.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 8106515..3bf6c33 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1770,13 +1770,14 @@ static void scsi_request_fn(struct request_queue *q)
struct Scsi_Host *shost;
struct scsi_cmnd *cmd;
struct request *req;
+ int i;
/*
- * To start with, we keep looping until the queue is empty, or until
- * the host is no longer able to accept any more requests.
+ * Loop until the queue is empty, until the host is no longer able to
+ * accept any more requests or until 256 requests have been processed.
*/
shost = sdev->host;
- for (;;) {
+ for (i = 256; i > 0; i--) {
int rtn;
/*
* get next queueable request. We do this early to make sure
@@ -1861,6 +1862,9 @@ static void scsi_request_fn(struct request_queue *q)
spin_lock_irq(q->queue_lock);
}
+ if (unlikely(i == 0))
+ blk_delay_queue(q, 0);
+
return;
host_not_ready:
--
2.7.3
--
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