Symmetry is still broken on firmware crash (at least with 6174). ath10k_pci_hif_stop gets called twice, once from the driver restart (warm restart) and once from ieee80211 start (cold restart), resulting in napi_synchrionize/napi_disable getting called twice and sticking the driver in an infinite wait loop (napi_synchronize waits until NAPI_STATE_SCHED is off, while napi_disable leaves NAPI_STATE_SCHED to on when leaving).
> On Feb 6, 2017, at 5:04 AM, Mohammed Shafi Shajakhan <mohammed@xxxxxxxxxxxxxx> wrote:
>
> Hi Kalle,
>
> the change suggested by you helps, and the device probe, scan
> is successful as well. Still good to have this change part of your
> basic sanity and regression testing !
>
> regards,
> shafi
>
> On Wed, Jan 25, 2017 at 01:46:28PM +0000, Valo, Kalle wrote:
>> Kalle Valo <kvalo@xxxxxxxxxxxxxxxx> writes:
>>
>>> Mohammed Shafi Shajakhan <mohammed@xxxxxxxxxxxxxxxx> writes:
>>>
>>>> From: Mohammed Shafi Shajakhan <mohammed@xxxxxxxxxxxxxxxx>
>>>>
>>>> This fixes the below crash when ath10k probe firmware fails,
>>>> NAPI polling tries to access a rx ring resource which was never
>>>> allocated, fix this by disabling NAPI right away once the probe
>>>> firmware fails by calling 'ath10k_hif_stop'. Its good to note
>>>> that the error is never propogated to 'ath10k_pci_probe' when
>>>> ath10k_core_register fails, so calling 'ath10k_hif_stop' to cleanup
>>>> PCI related things seems to be ok
>>>>
>>>> BUG: unable to handle kernel NULL pointer dereference at (null)
>>>> IP: __ath10k_htt_rx_ring_fill_n+0x19/0x230 [ath10k_core]
>>>> __ath10k_htt_rx_ring_fill_n+0x19/0x230 [ath10k_core]
>>>>
>>>> Call Trace:
>>>>
>>>> [<ffffffffa113ec62>] ath10k_htt_rx_msdu_buff_replenish+0x42/0x90
>>>> [ath10k_core]
>>>> [<ffffffffa113f393>] ath10k_htt_txrx_compl_task+0x433/0x17d0
>>>> [ath10k_core]
>>>> [<ffffffff8114406d>] ? __wake_up_common+0x4d/0x80
>>>> [<ffffffff811349ec>] ? cpu_load_update+0xdc/0x150
>>>> [<ffffffffa119301d>] ? ath10k_pci_read32+0xd/0x10 [ath10k_pci]
>>>> [<ffffffffa1195b17>] ath10k_pci_napi_poll+0x47/0x110 [ath10k_pci]
>>>> [<ffffffff817863af>] net_rx_action+0x20f/0x370
>>>>
>>>> Reported-by: Ben Greear <greearb@xxxxxxxxxxxxxxx>
>>>> Fixes: 3c97f5de1f28 ("ath10k: implement NAPI support")
>>>> Signed-off-by: Mohammed Shafi Shajakhan <mohammed@xxxxxxxxxxxxxxxx>
>>>
>>> Is there an easy way to reproduce this bug? I don't see it on my x86
>>> laptop with qca988x and I call rmmod all the time. I would like to test
>>> this myself.
>>>
>>>> --- a/drivers/net/wireless/ath/ath10k/core.c
>>>> +++ b/drivers/net/wireless/ath/ath10k/core.c
>>>> @@ -2164,6 +2164,7 @@ static int ath10k_core_probe_fw(struct ath10k *ar)
>>>> ath10k_core_free_firmware_files(ar);
>>>>
>>>> err_power_down:
>>>> + ath10k_hif_stop(ar);
>>>> ath10k_hif_power_down(ar);
>>>>
>>>> return ret;
>>>
>>> This breaks the symmetry, we should not be calling ath10k_hif_stop() if
>>> we haven't called ath10k_hif_start() from the same function. This can
>>> just create a bigger mess later, for example with other bus support like
>>> sdio or usb. In theory it should enough that we call
>>> ath10k_hif_power_down() and pci.c does the rest correctly "behind the
>>> scenes".
>>>
>>> I investigated this a bit and I think the real cause is that we call
>>> napi_enable() from ath10k_pci_hif_power_up() and napi_disable() from
>>> ath10k_pci_hif_stop(). Does anyone remember why?
>>>
>>> I was expecting that we would call napi_enable()/napi_disable() either
>>> in ath10k_hif_power_up/down() or ath10k_hif_start()/stop(), but not
>>> mixed like it's currently.
>>
>> So below is something I was thinking of, now napi_enable() is called
>> from ath10k_hif_start() and napi_disable() from ath10k_hif_stop(). Would
>> that work?
>>
>> --- a/drivers/net/wireless/ath/ath10k/pci.c
>> +++ b/drivers/net/wireless/ath/ath10k/pci.c
>> @@ -1648,6 +1648,8 @@ static int ath10k_pci_hif_start(struct ath10k *ar)
>>
>> ath10k_dbg(ar, ATH10K_DBG_BOOT, "boot hif start\n");
>>
>> + napi_enable(&ar->napi);
>> +
>> ath10k_pci_irq_enable(ar);
>> ath10k_pci_rx_post(ar);
>>
>> @@ -2532,7 +2534,6 @@ static int ath10k_pci_hif_power_up(struct ath10k *ar)
>> ath10k_err(ar, "could not wake up target CPU: %d\n", ret);
>> goto err_ce;
>> }
>> - napi_enable(&ar->napi);
>>
>> return 0;
>>
>> --
>> Kalle Valo
>
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