* [PATCH] slip: fix NOHZ local_softirq_pending 08 warning
@ 2011-08-05 19:23 Matvejchikov Ilya
2011-08-08 5:14 ` David Miller
2011-08-09 17:07 ` Oliver Hartkopp
0 siblings, 2 replies; 6+ messages in thread
From: Matvejchikov Ilya @ 2011-08-05 19:23 UTC (permalink / raw)
To: netdev
When using nanosleep() in an userspace application we get a ratelimit warning:
NOHZ: local_softirq_pending 08
According to 481a8199142c050b72bff8a1956a49fd0a75bbe0 the problem is caused by
netif_rx() function. This patch replaces netif_rx() with netif_rx_ni() which
has to be used from process/softirq context.
Signed-off-by: Matvejchikov Ilya <matvejchikov@gmail.com>
---
drivers/net/slip.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/drivers/net/slip.c b/drivers/net/slip.c
index f11b3f3..4c61753 100644
--- a/drivers/net/slip.c
+++ b/drivers/net/slip.c
@@ -367,7 +367,7 @@ static void sl_bump(struct slip *sl)
memcpy(skb_put(skb, count), sl->rbuff, count);
skb_reset_mac_header(skb);
skb->protocol = htons(ETH_P_IP);
- netif_rx(skb);
+ netif_rx_ni(skb);
dev->stats.rx_packets++;
}
--
1.7.4.1
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH] slip: fix NOHZ local_softirq_pending 08 warning
2011-08-05 19:23 [PATCH] slip: fix NOHZ local_softirq_pending 08 warning Matvejchikov Ilya
@ 2011-08-08 5:14 ` David Miller
2011-08-09 17:07 ` Oliver Hartkopp
1 sibling, 0 replies; 6+ messages in thread
From: David Miller @ 2011-08-08 5:14 UTC (permalink / raw)
To: matvejchikov; +Cc: netdev
From: Matvejchikov Ilya <matvejchikov@gmail.com>
Date: Fri, 5 Aug 2011 23:23:51 +0400
> When using nanosleep() in an userspace application we get a ratelimit warning:
>
> NOHZ: local_softirq_pending 08
>
> According to 481a8199142c050b72bff8a1956a49fd0a75bbe0 the problem is caused by
> netif_rx() function. This patch replaces netif_rx() with netif_rx_ni() which
> has to be used from process/softirq context.
>
> Signed-off-by: Matvejchikov Ilya <matvejchikov@gmail.com>
Applied, thanks.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] slip: fix NOHZ local_softirq_pending 08 warning
2011-08-05 19:23 [PATCH] slip: fix NOHZ local_softirq_pending 08 warning Matvejchikov Ilya
2011-08-08 5:14 ` David Miller
@ 2011-08-09 17:07 ` Oliver Hartkopp
2011-08-10 7:47 ` Matvejchikov Ilya
1 sibling, 1 reply; 6+ messages in thread
From: Oliver Hartkopp @ 2011-08-09 17:07 UTC (permalink / raw)
To: matvejchikov; +Cc: netdev, Alan Cox
Hello Ilya,
is the processing of characters in the tty input stream for line disciplines
*always* done in softirq context???
If so, i would send a patch for drivers/net/can/slcan.c too ...
Thanks,
Oliver
On 05.08.2011 21:23, Matvejchikov Ilya wrote:
> When using nanosleep() in an userspace application we get a ratelimit warning:
>
> NOHZ: local_softirq_pending 08
>
> According to 481a8199142c050b72bff8a1956a49fd0a75bbe0 the problem is caused by
> netif_rx() function. This patch replaces netif_rx() with netif_rx_ni() which
> has to be used from process/softirq context.
>
> Signed-off-by: Matvejchikov Ilya <matvejchikov@gmail.com>
> ---
> drivers/net/slip.c | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/net/slip.c b/drivers/net/slip.c
> index f11b3f3..4c61753 100644
> --- a/drivers/net/slip.c
> +++ b/drivers/net/slip.c
> @@ -367,7 +367,7 @@ static void sl_bump(struct slip *sl)
> memcpy(skb_put(skb, count), sl->rbuff, count);
> skb_reset_mac_header(skb);
> skb->protocol = htons(ETH_P_IP);
> - netif_rx(skb);
> + netif_rx_ni(skb);
> dev->stats.rx_packets++;
> }
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] slip: fix NOHZ local_softirq_pending 08 warning
2011-08-09 17:07 ` Oliver Hartkopp
@ 2011-08-10 7:47 ` Matvejchikov Ilya
2011-08-10 9:28 ` Alan Cox
0 siblings, 1 reply; 6+ messages in thread
From: Matvejchikov Ilya @ 2011-08-10 7:47 UTC (permalink / raw)
To: Oliver Hartkopp; +Cc: netdev, Alan Cox
Oliver,
As I see it, there is the following call chain of the netif_rx_ni() in
the slip (or slcan) driver:
[flush_to_ldisc] -> [disc->ops->receive_buf] -> [slip_unesc] ->
[sl_bump] -> [netif_rx_ni]
So flush_to_ldisc() may be called:
1) From tty_flush_to_ldisc() with flush_work and as it mentioned
must not be called from IRQ context.
2) From input_available_p() which can be called from n_tty_read() or
n_tty_poll(), so it's the user's context.
2) From tty_flip_buffer_push() which schedules the flush_to_ldisc to
work or calls it directly if the tty->low_latency set.
So the only thing we must take into account that with tty->low_latency
set we can be in IRQ context when doing with netif_rx_ni(). But if we
are using netif_rx_ni() we can handle both IRQ and softirq contexts
well as if there are any softirq pending netif_rx_ni() calls
do_softirq() with preemtion disabled. Then do_softirq() checks if
there is an IRQ context and does nothing if so.
So, I think it's correct to change netif_rx() with the netif_rx_ni().
2011/8/9 Oliver Hartkopp <socketcan@hartkopp.net>:
> Hello Ilya,
>
> is the processing of characters in the tty input stream for line disciplines
> *always* done in softirq context???
>
> If so, i would send a patch for drivers/net/can/slcan.c too ...
>
> Thanks,
> Oliver
>
> On 05.08.2011 21:23, Matvejchikov Ilya wrote:
>> When using nanosleep() in an userspace application we get a ratelimit warning:
>>
>> NOHZ: local_softirq_pending 08
>>
>> According to 481a8199142c050b72bff8a1956a49fd0a75bbe0 the problem is caused by
>> netif_rx() function. This patch replaces netif_rx() with netif_rx_ni() which
>> has to be used from process/softirq context.
>>
>> Signed-off-by: Matvejchikov Ilya <matvejchikov@gmail.com>
>> ---
>> drivers/net/slip.c | 2 +-
>> 1 files changed, 1 insertions(+), 1 deletions(-)
>>
>> diff --git a/drivers/net/slip.c b/drivers/net/slip.c
>> index f11b3f3..4c61753 100644
>> --- a/drivers/net/slip.c
>> +++ b/drivers/net/slip.c
>> @@ -367,7 +367,7 @@ static void sl_bump(struct slip *sl)
>> memcpy(skb_put(skb, count), sl->rbuff, count);
>> skb_reset_mac_header(skb);
>> skb->protocol = htons(ETH_P_IP);
>> - netif_rx(skb);
>> + netif_rx_ni(skb);
>> dev->stats.rx_packets++;
>> }
>>
>
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] slip: fix NOHZ local_softirq_pending 08 warning
2011-08-10 7:47 ` Matvejchikov Ilya
@ 2011-08-10 9:28 ` Alan Cox
2011-08-10 14:33 ` Oliver Hartkopp
0 siblings, 1 reply; 6+ messages in thread
From: Alan Cox @ 2011-08-10 9:28 UTC (permalink / raw)
To: matvejchikov; +Cc: Oliver Hartkopp, netdev
> 2) From tty_flip_buffer_push() which schedules the flush_to_ldisc to
> work or calls it directly if the tty->low_latency set.
>
> So the only thing we must take into account that with tty->low_latency
> set we can be in IRQ context when doing with netif_rx_ni(). But if we
A driver is not permitted to directly call into flush_to_ldisc from an
interrupt so that case doesn't happen.
Alan
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] slip: fix NOHZ local_softirq_pending 08 warning
2011-08-10 9:28 ` Alan Cox
@ 2011-08-10 14:33 ` Oliver Hartkopp
0 siblings, 0 replies; 6+ messages in thread
From: Oliver Hartkopp @ 2011-08-10 14:33 UTC (permalink / raw)
To: Alan Cox, matvejchikov; +Cc: netdev
On 10.08.2011 11:28, Alan Cox wrote:
>> 2) From tty_flip_buffer_push() which schedules the flush_to_ldisc to
>> work or calls it directly if the tty->low_latency set.
>>
>> So the only thing we must take into account that with tty->low_latency
>> set we can be in IRQ context when doing with netif_rx_ni(). But if we
>
> A driver is not permitted to directly call into flush_to_ldisc from an
> interrupt so that case doesn't happen.
>
Thanks to both of you for the explanation!
I'll send a patch for slcan.c then.
Best regards,
Oliver
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2011-08-10 14:33 UTC | newest]
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2011-08-05 19:23 [PATCH] slip: fix NOHZ local_softirq_pending 08 warning Matvejchikov Ilya
2011-08-08 5:14 ` David Miller
2011-08-09 17:07 ` Oliver Hartkopp
2011-08-10 7:47 ` Matvejchikov Ilya
2011-08-10 9:28 ` Alan Cox
2011-08-10 14:33 ` Oliver Hartkopp
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