* [PATCH 1/3] kernel/kthread.c: Avoid CPU lockups
2016-03-28 21:48 [PATCH 0/3] Improve block layer scheduling fairness Bart Van Assche
@ 2016-03-28 21:48 ` Bart Van Assche
2016-03-28 21:49 ` [PATCH 2/3] block: Limit work processed in softirq context Bart Van Assche
2016-03-28 21:50 ` [PATCH 3/3] Avoid that I/O completion processing triggers lockup complaints Bart Van Assche
2 siblings, 0 replies; 4+ messages in thread
From: Bart Van Assche @ 2016-03-28 21:48 UTC (permalink / raw)
To: Tejun Heo
Cc: Jens Axboe, James Bottomley, Martin K. Petersen, Mike Snitzer,
linux-scsi@vger.kernel.org
Avoid that complaints similar to the one below are reported against
a debug kernel:
NMI watchdog: BUG: soft lockup - CPU#1 stuck for 22s! [kdmwork-25 4:2:23313]
irq event stamp: 16320042
hardirqs last enabled at (16320041): [<ffffffff815992c7>] _raw_spin_unlock_irq+0x27/0x40
hardirqs last disabled at (16320042): [<ffff8803ffbe3cd8>] 0xffff8803ffbe3cd8
softirqs last enabled at (16319960): [<ffffffff8105bcdb>] __do_softirq+0x1cb/0x230
softirqs last disabled at (16319715): [<ffffffff8105bec8>] irq_exit+0xa8/0xb0
CPU: 1 PID: 23313 Comm: kdmwork-254:2
RIP: 0010:[<ffffffff815992cf>] [<ffffffff815992cf>] _raw_spin_unlock_irq+0x2f/0x40
Call Trace:
[<ffffffff813f702f>] scsi_request_fn+0x11f/0x630
[<ffffffff812977fe>] __blk_run_queue+0x2e/0x40
[<ffffffff81297065>] __elv_add_request+0x75/0x1f0
[<ffffffff8129ba91>] blk_insert_cloned_request+0x101/0x190
[<ffffffffa0189f1a>] map_request+0x16a/0x1b0 [dm_mod]
[<ffffffffa0189f7d>] map_tio_request+0x1d/0x40 [dm_mod]
[<ffffffff81077812>] kthread_worker_fn+0x82/0x1a0
[<ffffffff8107771a>] kthread+0xea/0x100
[<ffffffff81599b72>] ret_from_fork+0x22/0x40
Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
---
kernel/kthread.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/kernel/kthread.c b/kernel/kthread.c
index 9ff173d..516ca6b 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -593,6 +593,7 @@ repeat:
if (work) {
__set_current_state(TASK_RUNNING);
work->func(work);
+ cond_resched_rcu_qs();
} else if (!freezing(current))
schedule();
--
2.7.3
^ permalink raw reply related [flat|nested] 4+ messages in thread* [PATCH 2/3] block: Limit work processed in softirq context
2016-03-28 21:48 [PATCH 0/3] Improve block layer scheduling fairness Bart Van Assche
2016-03-28 21:48 ` [PATCH 1/3] kernel/kthread.c: Avoid CPU lockups Bart Van Assche
@ 2016-03-28 21:49 ` Bart Van Assche
2016-03-28 21:50 ` [PATCH 3/3] Avoid that I/O completion processing triggers lockup complaints Bart Van Assche
2 siblings, 0 replies; 4+ messages in thread
From: Bart Van Assche @ 2016-03-28 21:49 UTC (permalink / raw)
To: Jens Axboe
Cc: Tejun Heo, James Bottomley, Martin K. Petersen, Mike Snitzer,
linux-scsi@vger.kernel.org
Avoid that complaints like the one below are reported against a
debug kernel:
NMI watchdog: BUG: soft lockup - CPU#1 stuck for 22s! [disk11_0:2708]
irq event stamp: 17120809
hardirqs last enabled at (17120808): [<ffffffff81599191>] _raw_spin_unlock_irqrestore+0x31/0x50
hardirqs last disabled at (17120809): [<ffff88046f223bd0>] 0xffff88046f223bd0
softirqs last enabled at (17120794): [<ffffffffa060aa67>] scst_check_blocked_dev+0x77/0x1c0 [scst]
softirqs last disabled at (17120795): [<ffffffff8159acbc>] do_softirq_own_stack+0x1c/0x30
RIP: 0010:[<ffffffff81599193>] [<ffffffff81599193>] _raw_spin_unlock_irqrestore+0x33/0x50
Call Trace:
<IRQ>
[<ffffffff81171450>] free_debug_processing+0x270/0x3a0
[<ffffffff8117277a>] __slab_free+0x17a/0x2c0
[<ffffffff81172a74>] kmem_cache_free+0x1b4/0x1d0
[<ffffffff8111a6c2>] mempool_free_slab+0x12/0x20
[<ffffffff8111a846>] mempool_free+0x26/0x80
[<ffffffff81294cb9>] bio_free+0x49/0x60
[<ffffffff81294cee>] bio_put+0x1e/0x30
[<ffffffffa0199d31>] end_clone_bio+0x21/0x70 [dm_mod]
[<ffffffff81294d52>] bio_endio+0x52/0x60
[<ffffffff8129aaec>] blk_update_request+0x7c/0x2a0
[<ffffffff813f4a8e>] scsi_end_request+0x2e/0x1d0
[<ffffffff813f7674>] scsi_io_completion+0xb4/0x610
[<ffffffff813ee79a>] scsi_finish_command+0xca/0x120
[<ffffffff813f6ef0>] scsi_softirq_done+0x120/0x140
[<ffffffff812a26e6>] blk_done_softirq+0x76/0x90
[<ffffffff8105bc1f>] __do_softirq+0x10f/0x230
[<ffffffff8159acbc>] do_softirq_own_stack+0x1c/0x30
<EOI>
Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
---
block/blk-softirq.c | 20 ++++++++++++++++++++
1 file changed, 20 insertions(+)
diff --git a/block/blk-softirq.c b/block/blk-softirq.c
index 53b1737..d4d2fe4 100644
--- a/block/blk-softirq.c
+++ b/block/blk-softirq.c
@@ -21,10 +21,22 @@ static DEFINE_PER_CPU(struct list_head, blk_cpu_done);
static void blk_done_softirq(struct softirq_action *h)
{
struct list_head *cpu_list, local_list;
+ struct request *e;
+ bool reraise = false;
+ int i = 0;
local_irq_disable();
cpu_list = this_cpu_ptr(&blk_cpu_done);
+ list_for_each_entry(e, cpu_list, ipi_list) {
+ if (++i < 256)
+ continue;
+ list_cut_position(&local_list, cpu_list, &e->ipi_list);
+ reraise = true;
+ goto enable_irq;
+ }
list_replace_init(cpu_list, &local_list);
+
+enable_irq:
local_irq_enable();
while (!list_empty(&local_list)) {
@@ -34,6 +46,14 @@ static void blk_done_softirq(struct softirq_action *h)
list_del_init(&rq->ipi_list);
rq->q->softirq_done_fn(rq);
}
+
+ if (!reraise)
+ return;
+
+ local_irq_disable();
+ if (!list_empty(cpu_list))
+ raise_softirq_irqoff(BLOCK_SOFTIRQ);
+ local_irq_enable();
}
#ifdef CONFIG_SMP
--
2.7.3
^ permalink raw reply related [flat|nested] 4+ messages in thread* [PATCH 3/3] Avoid that I/O completion processing triggers lockup complaints
2016-03-28 21:48 [PATCH 0/3] Improve block layer scheduling fairness Bart Van Assche
2016-03-28 21:48 ` [PATCH 1/3] kernel/kthread.c: Avoid CPU lockups Bart Van Assche
2016-03-28 21:49 ` [PATCH 2/3] block: Limit work processed in softirq context Bart Van Assche
@ 2016-03-28 21:50 ` Bart Van Assche
2 siblings, 0 replies; 4+ messages in thread
From: Bart Van Assche @ 2016-03-28 21:50 UTC (permalink / raw)
To: James Bottomley, Martin K. Petersen
Cc: Mike Snitzer, Tejun Heo, Jens Axboe, linux-scsi@vger.kernel.org
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@sandisk.com>
---
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
^ permalink raw reply related [flat|nested] 4+ messages in thread