netdev - Re: WARN_ON_ONCE(work > weight) in napi

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Date:   Tue, 11 Jul 2017 20:28:44 +0300
From:   Andrey Ryabinin <aryabinin@...tuozzo.com>
To:     Ryan Hsu <ryanhsu@....qualcomm.com>,
        Kalle Valo <kvalo@....qualcomm.com>
Cc:     Networking <netdev@...r.kernel.org>,
        linux-wireless <linux-wireless@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "ath10k@...ts.infradead.org" <ath10k@...ts.infradead.org>
Subject: Re: WARN_ON_ONCE(work > weight) in napi_poll()

On 07/11/2017 12:24 AM, Ryan Hsu wrote:
> On 07/04/2017 08:59 AM, Andrey Ryabinin wrote:
> 
>> On 07/04/2017 04:49 PM, Kalle Valo wrote:
>>> Andrey Ryabinin <aryabinin@...tuozzo.com> writes:
>>>
>>>> I occasionally hit WARN_ON_ONCE(work > weight); in napi_poll() on a
>>>> laptop with ath10k card.
>>>>
>>>>
>>>> [37207.593370] ------------[ cut here ]------------
>>>> [37207.593380] WARNING: CPU: 0 PID: 7 at ../net/core/dev.c:5274
>>>> net_rx_action+0x258/0x360
>>>> [37207.593381] Modules linked in: snd_hda_codec_realtek snd_soc_skl
>>>> snd_hda_codec_generic snd_soc_skl_ipc snd_soc_sst_ipc snd_soc_sst_dsp
>>>> snd_hda_ext_core snd_soc_sst_match snd_soc_core rtsx_pci_sdmmc
>>>> mmc_core snd_pcm_dmaengine x86_pkg_temp_thermal snd_hda_intel uvcvideo
>>>> kvm_intel videobuf2_vmalloc kvm snd_hda_codec snd_hwdep btusb
>>>> videobuf2_memops btintel snd_hda_core videobuf2_v4l2 bluetooth
>>>> irqbypass snd_pcm videobuf2_core crc32c_intel videodev mei_me mei
>>>> rtsx_pci intel_lpss_pci intel_lpss_acpi intel_vbtn intel_lpss mfd_core
>>>> tpm_tis intel_hid tpm_tis_core tpm efivarfs
>>>> [37207.593430] CPU: 0 PID: 7 Comm: ksoftirqd/0 Not tainted 4.11.7 #28
>>>> [37207.593432] Hardware name: Dell Inc. XPS 13 9360/0839Y6, BIOS 1.3.5 05/08/2017
>>> What firmware and hardware versions exactly? The dmesg output when
>>> ath10k loads is preferred. As you are using XPS 13 I'm guessing it's one
>>> of QCA6174 family.
>>>
>> Yes it's qca6174.
>>
>> $ dmesg |grep ath10
>> [    0.624828] ath10k_pci 0000:3a:00.0: enabling device (0000 -> 0002)
>> [    0.626370] ath10k_pci 0000:3a:00.0: pci irq msi oper_irq_mode 2 irq_mode 0 reset_mode 0
>> [    0.837862] ath10k_pci 0000:3a:00.0: qca6174 hw3.2 target 0x05030000 chip_id 0x00340aff sub 1a56:1535
>> [    0.837863] ath10k_pci 0000:3a:00.0: kconfig debug 0 debugfs 1 tracing 0 dfs 0 testmode 0
>> [    0.838388] ath10k_pci 0000:3a:00.0: firmware ver WLAN.RM.2.0-00180-QCARMSWPZ-1 api 4 features wowlan,ignore-otp,no-4addr-pad crc32 75dee6c5
>> [    0.900606] ath10k_pci 0000:3a:00.0: board_file api 2 bmi_id N/A crc32 19644295
>> [    3.020681] ath10k_pci 0000:3a:00.0: htt-ver 3.26 wmi-op 4 htt-op 3 cal otp max-sta 32 raw 0 hwcrypto 1
>> [    9.574087] ath10k_pci 0000:3a:00.0 wlp58s0: renamed from wlan0
>>
> 
> I can't reproduce of this past few days, not sure if this is due to the amsdu packets received from AP, would you mind share what Ap you're using?
> And if there any specific steps you're doing?
> 

The bug is quite rare, and I don't know how to reproduce it on purpose. It just happens once in several days
and it happened with different APs. 

Perhaps you could think of some debug patch that could help to understand what's going on? I could carry it and will
report if warning hits again. 

FYI I applied small debug patch bellow, just to understand where exactly we bail out with too big quota.

---
 drivers/net/wireless/ath/ath10k/htt_rx.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/net/wireless/ath/ath10k/htt_rx.c b/drivers/net/wireless/ath/ath10k/htt_rx.c
index 02a3fc81fbe3..02b0cc6ec671 100644
--- a/drivers/net/wireless/ath/ath10k/htt_rx.c
+++ b/drivers/net/wireless/ath/ath10k/htt_rx.c
@@ -2548,6 +2548,8 @@ int ath10k_htt_txrx_compl_task(struct ath10k *ar, int budget)
                        goto exit;
                }
        }
+       if (quota > budget)
+               pr_err("#1 quota too big %d %d %d\n", quota, budget, num_rx_msdus);
 
        while (quota < budget) {
                /* no more data to receive */
@@ -2568,6 +2570,8 @@ int ath10k_htt_txrx_compl_task(struct ath10k *ar, int budget)
                        goto exit;
                }
        }
+       if (quota > budget)
+               pr_err("#2 quota too big %d %d %d\n", quota, budget, num_rx_msdus);
 
        /* From NAPI documentation:
         *  The napi poll() function may also process TX completions, in which
--


It gave me this:

[118648.825347] #1 quota too big 72 64 16
[118648.825351] #2 quota too big 72 64 16
[118648.825471] ------------[ cut here ]------------
[118648.825484] WARNING: CPU: 0 PID: 0 at ../net/core/dev.c:5274 net_rx_action+0x258/0x360

So this means that we didn't met the condition bellow, i.e. skb_queue_empty() returned true.

	ath10k_htt_txrx_compl_task():

		if ((quota > ATH10K_NAPI_QUOTA_LIMIT) &&
		    !skb_queue_empty(&htt->rx_in_ord_compl_q)) {
			resched_napi = true;
			goto exit;
		}

> Also WLAN.RM.2.0-00180-QCARMSWPZ-1 firmware is a bit old, could you also update firmware to give it a try?
> https://github.com/kvalo/ath10k-firmware/tree/master/QCA6174/hw3.0/4.4
> 

Will try.