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Re: [PATCH v6 net-next 17/17] net: qualcomm: add QCA7000 UART driver

From Stefan Wahren <stefan.wahren@i2se.com>
Newsgroups linux.kernel
Subject Re: [PATCH v6 net-next 17/17] net: qualcomm: add QCA7000 UART driver
Date 2017-05-24 11:10 +0200
Message-ID <tKAsO-ma-17@gated-at.bofh.it> (permalink)
References <tKhTb-3GR-3@gated-at.bofh.it> <tKhTb-3GR-5@gated-at.bofh.it> <tKmzw-6Qv-21@gated-at.bofh.it> <tKnOW-7FB-17@gated-at.bofh.it> <tKpnJ-w5-53@gated-at.bofh.it>
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Am 23.05.2017 um 23:01 schrieb Lino Sanfilippo:
> On 23.05.2017 21:38, Stefan Wahren wrote:
>>> Lino Sanfilippo <LinoSanfilippo@gmx.de> hat am 23. Mai 2017 um 20:16 geschrieben:
>>>
>>> I suggest to avoid this possible race by first unregistering the netdevice and then 
>>> calling cancel_work_sync().
>> What makes you sure that's safe to unregister the netdev while the tx work queue is possibly active?
> unregister_netdevice() calls netdev_close() if the interface is still up. netdev_close() calls flush_work()
> so the unregistration is delayed until the tx work function is finished. Furthermore both close() and
> tx work are synchronized by means of the qca->lock which also guarantees that unregister_netdevice() wont
> be finished until the tx work is done.
>

Thanks for the explanation. I suspect there could be the same race
between serdev_device_close() and the tx work queue.

So i would propose a variant of your original suggestion:

unregister_netdev(qca->net_dev);

/* Flush any pending characters in the driver. */
serdev_device_close(serdev);
cancel_work_sync(&qca->tx_work);

Since we have the same pattern in the error path of the probe function,
the same applies there.

Stefan

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Thread

[PATCH v6 net-next 17/17] net: qualcomm: add QCA7000 UART driver Stefan Wahren <stefan.wahren@i2se.com> - 2017-05-23 15:20 +0200
  Re: [PATCH v6 net-next 17/17] net: qualcomm: add QCA7000 UART driver Lino Sanfilippo <LinoSanfilippo@gmx.de> - 2017-05-23 20:20 +0200
    Re: [PATCH v6 net-next 17/17] net: qualcomm: add QCA7000 UART  driver Stefan Wahren <stefan.wahren@i2se.com> - 2017-05-23 21:40 +0200
      Re: [PATCH v6 net-next 17/17] net: qualcomm: add QCA7000 UART driver Lino Sanfilippo <LinoSanfilippo@gmx.de> - 2017-05-23 23:20 +0200
        Re: [PATCH v6 net-next 17/17] net: qualcomm: add QCA7000 UART driver Stefan Wahren <stefan.wahren@i2se.com> - 2017-05-24 11:10 +0200
          [PATCH v7 net-next 17/17] net: qualcomm: add QCA7000 UART driver Stefan Wahren <stefan.wahren@i2se.com> - 2017-05-24 11:40 +0200
          [PATCH RESEND v7 net-next 17/17] net: qualcomm: add QCA7000 UART driver Stefan Wahren <stefan.wahren@i2se.com> - 2017-05-24 11:40 +0200
            Re: [PATCH RESEND v7 net-next 17/17] net: qualcomm: add QCA7000  UART driver "Lino Sanfilippo" <LinoSanfilippo@gmx.de> - 2017-05-24 16:30 +0200
              Re: [PATCH RESEND v7 net-next 17/17] net: qualcomm: add QCA7000 UART  driver Stefan Wahren <stefan.wahren@i2se.com> - 2017-05-24 16:40 +0200
          Aw: Re: [PATCH v6 net-next 17/17] net: qualcomm: add QCA7000 UART  driver "Lino Sanfilippo" <LinoSanfilippo@gmx.de> - 2017-05-24 16:30 +0200

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