lkml.org 
[lkml]   [2014]   [Jan]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[REGRESSION][BISECTED] 3.10.26: net_dma: mark broken (b69ec589136c)
For Xeon machines in config we have:
CONFIG_NET_DMA=y
# CONFIG_ASYNC_TX_DMA is not set
# CONFIG_DMATEST is not set
CONFIG_DCA=m

"net_dma: mark broken" changed it to (no CONFIG_NET_DMA):
# CONFIG_ASYNC_TX_DMA is not set
# CONFIG_DMATEST is not set
CONFIG_DMA_ENGINE_RAID=y
CONFIG_DCA=m

Since this commit, we started to observe that after machine reboots there
is some change (1 out of 10) that ksoftirqd/0 will eat 100% CPU#0.
In this case I see huge number of tasklets executed on CPU#0 (about a million
each second).

To reproduce I just reboot machine and check ksoftirqd/0 CPU usage, if it's <5%,
reboot machine again.

I added trace_printk into tasklet_action and I see the same tasklet
"executed" (it's disabled) over and over:
ksoftirqd/0-3 [000] ..s. 65.281375: tasklet_action: t=ffff88061e5cddc0 func=ioat3_cleanup_event [ioatdma] count=1
ksoftirqd/0-3 [000] ..s. 65.281376: tasklet_action: t=ffff88061e5cddc0 func=ioat3_cleanup_event [ioatdma] count=1
ksoftirqd/0-3 [000] ..s. 65.281376: tasklet_action: t=ffff88061e5cddc0 func=ioat3_cleanup_event [ioatdma] count=1
ksoftirqd/0-3 [000] ..s. 65.281376: tasklet_action: t=ffff88061e5cddc0 func=ioat3_cleanup_event [ioatdma] count=1
ksoftirqd/0-3 [000] ..s. 65.281377: tasklet_action: t=ffff88061e5cddc0 func=ioat3_cleanup_event [ioatdma] count=1
ksoftirqd/0-3 [000] ..s. 65.281377: tasklet_action: t=ffff88061e5cddc0 func=ioat3_cleanup_event [ioatdma] count=1
ksoftirqd/0-3 [000] ..s. 65.281377: tasklet_action: t=ffff88061e5cddc0 func=ioat3_cleanup_event [ioatdma] count=1
ksoftirqd/0-3 [000] ..s. 65.281378: tasklet_action: t=ffff88061e5cddc0 func=ioat3_cleanup_event [ioatdma] count=1
ksoftirqd/0-3 [000] ..s. 65.281378: tasklet_action: t=ffff88061e5cddc0 func=ioat3_cleanup_event [ioatdma] count=1
ksoftirqd/0-3 [000] ..s. 65.281378: tasklet_action: t=ffff88061e5cddc0 func=ioat3_cleanup_event [ioatdma] count=1
ksoftirqd/0-3 [000] ..s. 65.281379: tasklet_action: t=ffff88061e5cddc0 func=ioat3_cleanup_event [ioatdma] count=1
ksoftirqd/0-3 [000] ..s. 65.281379: tasklet_action: t=ffff88061e5cddc0 func=ioat3_cleanup_event [ioatdma] count=1
ksoftirqd/0-3 [000] ..s. 65.281379: tasklet_action: t=ffff88061e5cddc0 func=ioat3_cleanup_event [ioatdma] count=1

Then I added more printk's and got the following (correct) trace for the case
when ksoftirqd/0 doesn't consume 100% CPU:
modprobe-650 [005] .... 9.553511: ioat_init_channel: tasklet_init(ffff880c13d72500)
migration/3-71 [003] d... 9.554049: complete: x=ffff88061a6f9df0 ret=cpu_stop_signal_done
migration/15-132 [015] d... 9.554790: complete: x=ffff880c15fe3df0 ret=cpu_stop_signal_done
modprobe-650 [005] ..s. 9.556690: ioat_dma_self_test: init_completion(ffff88061c2bfa18) ret=ioat3_dma_self_test [ioatdma]
modprobe-650 [005] .... 9.556693: ioat_dma_self_test: wait_for_completion(ffff88061c2bfa18, 750)
mount-620 [000] d.h. 9.556694: ioat_dma_do_interrupt_msix: tasklet_schedule(ffff880c13d72500)
mount-620 [000] d.h. 9.556695: __tasklet_schedule: t=ffff880c13d72500 ret=ioat_dma_do_interrupt_msix [ioatdma]
mount-620 [000] ..s. 9.556696: tasklet_action: t=ffff880627c03e98 func=ioat3_cleanup_event [ioatdma] count=0
mount-620 [000] ..s. 9.556699: ioat_dma_test_callback: complete(ffff88061c2bfa18) ret=__cleanup [ioatdma]
mount-620 [000] d.s. 9.556700: complete: x=ffff88061c2bfa18 ret=ioat_dma_test_callback [ioatdma]
mount-620 [000] d.H. 9.556704: ioat_dma_do_interrupt_msix: tasklet_schedule(ffff880c13d72500)
mount-620 [000] d.H. 9.556705: __tasklet_schedule: t=ffff880c13d72500 ret=ioat_dma_do_interrupt_msix [ioatdma]
mount-620 [000] ..s. 9.556705: tasklet_action: t=ffff880627c03e98 func=ioat3_cleanup_event [ioatdma] count=0
migration/10-107 [010] d... 9.558487: complete: x=ffff880c15f4fdf0 ret=cpu_stop_signal_done
modprobe-650 [011] .... 9.560545: ioat_dma_self_test: wait_for_completion returned tmo=750

And really weird trace when ksoftirqd/0 consumes 100% CPU:
modprobe-689 [014] .... 9.490260: ioat_init_channel: tasklet_init(ffff880c13c8b568)
migration/3-71 [003] d... 9.491727: complete: x=ffff88061a761df0 ret=cpu_stop_signal_done
migration/13-122 [013] d... 9.492212: complete: x=ffff880c15567df0 ret=cpu_stop_signal_done
migration/3-71 [003] d... 9.493098: complete: x=ffff880c15565df0 ret=cpu_stop_signal_done
modprobe-689 [014] ..s. 9.493655: ioat_dma_self_test: init_completion(ffff88061a503a18) ret=ioat3_dma_self_test [ioatdma]
modprobe-689 [014] .... 9.493657: ioat_dma_self_test: wait_for_completion(ffff88061a503a18, 750)
modprobe-689 [014] .... 9.494250: ioat_dma_self_test: wait_for_completion returned tmo=750
kthreadd-736 [002] d... 9.496220: complete: x=ffff880c143cfbe0 ret=kthread
migration/2-66 [002] d... 9.499974: complete: x=ffff880619c59df0 ret=cpu_stop_signal_done
migration/11-112 [011] d... 9.500705: complete: x=ffff880c15589df0 ret=cpu_stop_signal_done
migration/1-61 [001] d... 9.501807: complete: x=ffff88061a48ddf0 ret=cpu_stop_signal_done
modprobe-689 [014] .... 9.506554: ioat_init_channel: tasklet_init(ffff880c1363e358)
migration/3-71 [003] d... 9.506737: complete: x=ffff88061a7b1df0 ret=cpu_stop_signal_done
migration/13-122 [013] d... 9.508612: complete: x=ffff880c1570fdf0 ret=cpu_stop_signal_done
modprobe-689 [014] ..s. 9.508988: ioat_dma_self_test: init_completion(ffff88061a503a18) ret=ioat3_dma_self_test [ioatdma]
modprobe-689 [014] .... 9.508990: ioat_dma_self_test: wait_for_completion(ffff88061a503a18, 750)
migration/11-112 [011] d... 9.509157: complete: x=ffff88061a76ddf0 ret=cpu_stop_signal_done
migration/11-112 [011] d... 9.509998: complete: x=ffff880c14385df0 ret=cpu_stop_signal_done
migration/4-76 [004] d... 9.512649: complete: x=ffff880c155b1df0 ret=cpu_stop_signal_done
migration/10-107 [010] d... 9.513768: complete: x=ffff88061a773df0 ret=cpu_stop_signal_done
migration/8-97 [008] d... 9.515415: complete: x=ffff880c155b3df0 ret=cpu_stop_signal_done
migration/6-87 [006] d... 9.515475: complete: x=ffff880c155a5df0 ret=cpu_stop_signal_done
migration/11-112 [011] d... 9.515650: complete: x=ffff880c155a7df0 ret=cpu_stop_signal_done
migration/4-76 [004] d... 9.516355: complete: x=ffff880619c5bdf0 ret=cpu_stop_signal_done
migration/4-76 [004] d... 9.516492: complete: x=ffff880619c4bdf0 ret=cpu_stop_signal_done
migration/4-76 [004] d... 9.516882: complete: x=ffff880c1576ddf0 ret=cpu_stop_signal_done
migration/3-71 [003] d... 9.518353: complete: x=ffff880c15763df0 ret=cpu_stop_signal_done
migration/14-127 [014] d... 9.518737: complete: x=ffff880c15785df0 ret=cpu_stop_signal_done
migration/3-71 [003] d... 9.518947: complete: x=ffff880c15761df0 ret=cpu_stop_signal_done
migration/8-97 [008] d... 9.519121: complete: x=ffff88061ab03df0 ret=cpu_stop_signal_done
migration/8-97 [008] d... 9.519492: complete: x=ffff880c15b15df0 ret=cpu_stop_signal_done
migration/1-61 [001] d... 9.523569: complete: x=ffff880c15b2fdf0 ret=cpu_stop_signal_done
migration/3-71 [003] d... 9.524123: complete: x=ffff880619fc9df0 ret=cpu_stop_signal_done
modprobe-689 [008] ..s. 9.524370: ioat_dma_self_test: init_completion(ffff88061a503a18) ret=ioat3_dma_self_test [ioatdma]
modprobe-689 [008] .... 9.524372: ioat_dma_self_test: wait_for_completion(ffff88061a503a18, 750)
migration/1-61 [001] d... 9.524835: complete: x=ffff880c13e51df0 ret=cpu_stop_signal_done
ksoftirqd/14-128 [014] d.s. 9.525102: complete: x=ffff88061a7b1b20 ret=blk_end_sync_rq
ksoftirqd/3-72 [003] d.s. 9.526560: complete: x=ffff880c155b1b20 ret=blk_end_sync_rq
migration/9-102 [009] d... 9.526669: complete: x=ffff880c157e7df0 ret=cpu_stop_signal_done
kthreadd-768 [003] d... 9.526770: complete: x=ffff88061dbcfd00 ret=kthread
kthreadd-769 [012] d... 9.526833: complete: x=ffff88061dd29d00 ret=kthread
ksoftirqd/7-93 [007] d.s. 9.527077: complete: x=ffff880c1570fb20 ret=blk_end_sync_rq
kthreadd-771 [007] d... 9.527799: complete: x=ffff880c17403d00 ret=kthread
migration/7-92 [007] d... 9.527916: complete: x=ffff880c13e47df0 ret=cpu_stop_signal_done
modprobe-689 [003] .... 9.527917: ioat_dma_self_test: wait_for_completion returned tmo=750

.. later

ksoftirqd/0-3 [000] ..s. 65.281375: tasklet_action: t=ffff88061e5cddc0 func=ioat3_cleanup_event [ioatdma] count=1
ksoftirqd/0-3 [000] ..s. 65.281376: tasklet_action: t=ffff88061e5cddc0 func=ioat3_cleanup_event [ioatdma] count=1
ksoftirqd/0-3 [000] ..s. 65.281376: tasklet_action: t=ffff88061e5cddc0 func=ioat3_cleanup_event [ioatdma] count=1
... and forever

So nobody is completing the work (but wait_for_completion_timeout returns
without a timeout) and nobody schedules tasklet, but it somehow ends up
in the CPU#0 tasklet vector (disabled).
Any ideas what could be wrong and how I can further debug it?

If I put something like udelay(1000) in ioat_dma_self_test before
wait_for_completion_timeout I never see this issue.

Probably because we had NET_DMA=y, our NIC driver used DMA and somehow
masked the issue prior to this 'bad' commit.

This behavior also occurs on 3.13, I assume the reason is the same.

Here is where I placed trace_printk, just in case:
---
diff --git a/drivers/dma/ioat/dma.c b/drivers/dma/ioat/dma.c
index 17a2393b3e25..646f5f9da9e3 100644
--- a/drivers/dma/ioat/dma.c
+++ b/drivers/dma/ioat/dma.c
@@ -93,6 +93,7 @@ static irqreturn_t ioat_dma_do_interrupt_msix(int irq, void *data)
{
struct ioat_chan_common *chan = data;

+ trace_printk("tasklet_schedule(%p)\n", &chan->cleanup_task);
tasklet_schedule(&chan->cleanup_task);

return IRQ_HANDLED;
@@ -115,6 +116,7 @@ void ioat_init_channel(struct ioatdma_device *device, struct ioat_chan_common *c
init_timer(&chan->timer);
chan->timer.function = device->timer_fn;
chan->timer.data = data;
+ trace_printk("tasklet_init(%p)\n", &chan->cleanup_task);
tasklet_init(&chan->cleanup_task, device->cleanup_fn, data);
tasklet_disable(&chan->cleanup_task);
}
@@ -786,6 +788,7 @@ static void ioat_dma_test_callback(void *dma_async_param)
{
struct completion *cmp = dma_async_param;

+ trace_printk("complete(%p) ret=%pf\n", cmp, (void *)_RET_IP_);
complete(cmp);
}

@@ -844,6 +847,7 @@ int ioat_dma_self_test(struct ioatdma_device *device)
}

async_tx_ack(tx);
+ trace_printk("init_completion(%p) ret=%pf\n", &cmp, (void *)_RET_IP_);
init_completion(&cmp);
tx->callback = ioat_dma_test_callback;
tx->callback_param = &cmp;
@@ -855,7 +859,9 @@ int ioat_dma_self_test(struct ioatdma_device *device)
}
dma->device_issue_pending(dma_chan);

+ trace_printk("wait_for_completion(%p, %lu)\n", &cmp, msecs_to_jiffies(3000));
tmo = wait_for_completion_timeout(&cmp, msecs_to_jiffies(3000));
+ trace_printk("wait_for_completion returned tmo=%lu\n", msecs_to_jiffies(3000));

if (tmo == 0 ||
dma->device_tx_status(dma_chan, cookie, NULL)
diff --git a/drivers/dma/ioat/dma_v2.c b/drivers/dma/ioat/dma_v2.c
index b925e1b1d139..5483645ab83a 100644
--- a/drivers/dma/ioat/dma_v2.c
+++ b/drivers/dma/ioat/dma_v2.c
@@ -191,6 +191,8 @@ void ioat2_cleanup_event(unsigned long data)
{
struct ioat2_dma_chan *ioat = to_ioat2_chan((void *) data);

+ trace_printk("%pF\n", (void*)_RET_IP_);
+
ioat2_cleanup(ioat);
writew(IOAT_CHANCTRL_RUN, ioat->base.reg_base + IOAT_CHANCTRL_OFFSET);
}
@@ -303,6 +305,7 @@ void ioat2_timer_event(unsigned long data)
u64 status;

status = ioat_chansts(chan);
+ trace_printk("tasklet=%p\n", &chan->cleanup_task);

/* when halted due to errors check for channel
* programming errors before advancing the completion state
@@ -885,6 +888,8 @@ int ioat2_dma_probe(struct ioatdma_device *device, int dca)
struct ioat_chan_common *chan;
int err;

+ trace_printk("%pF\n", (void*)_RET_IP_);
+
device->enumerate_channels = ioat2_enumerate_channels;
device->reset_hw = ioat2_reset_hw;
device->cleanup_fn = ioat2_cleanup_event;
diff --git a/drivers/dma/ioat/dma_v3.c b/drivers/dma/ioat/dma_v3.c
index fa43a42ccc86..3e4e810ded12 100644
--- a/drivers/dma/ioat/dma_v3.c
+++ b/drivers/dma/ioat/dma_v3.c
@@ -748,6 +748,8 @@ static void ioat3_timer_event(unsigned long data)
dma_addr_t phys_complete;
u64 status;

+ trace_printk("tasklet=%p\n", &chan->cleanup_task);
+
status = ioat_chansts(chan);

/* when halted due to errors check for channel
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index e8b335016c52..b4e27cf0d983 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3267,6 +3267,7 @@ void complete(struct completion *x)
unsigned long flags;

spin_lock_irqsave(&x->wait.lock, flags);
+ trace_printk("x=%p ret=%pf\n", x, (void *)_RET_IP_);
x->done++;
__wake_up_common(&x->wait, TASK_NORMAL, 1, 0, NULL);
spin_unlock_irqrestore(&x->wait.lock, flags);
diff --git a/kernel/softirq.c b/kernel/softirq.c
index 787b3a032429..a4792c68ccd4 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -436,6 +436,7 @@ void __tasklet_schedule(struct tasklet_struct *t)
unsigned long flags;

local_irq_save(flags);
+ trace_printk("t=%p ret=%pf\n", t, (void *)_RET_IP_);
t->next = NULL;
*__this_cpu_read(tasklet_vec.tail) = t;
__this_cpu_write(tasklet_vec.tail, &(t->next));
@@ -486,6 +487,7 @@ static void tasklet_action(struct softirq_action *a)
list = list->next;

if (tasklet_trylock(t)) {
+ trace_printk("t=%p func=%pf count=%d\n", &t, t->func, atomic_read(&t->count));
if (!atomic_read(&t->count)) {
if (!test_and_clear_bit(TASKLET_STATE_SCHED, &t->state))
BUG();

\
 
 \ /
  Last update: 2014-01-27 19:01    [W:0.115 / U:15.088 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site