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Re: [Xen-devel] [PATCH] xen-netfront: wait xenbus state change when load module manually
- To: Jiri Slaby <jslaby@xxxxxxx>, Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>, Xiao Liang <xiliang@xxxxxxxxxx>, David Miller <davem@xxxxxxxxxxxxx>
- From: Juergen Gross <jgross@xxxxxxxx>
- Date: Fri, 7 Sep 2018 13:30:40 +0200
- Autocrypt: addr=jgross@xxxxxxxx; prefer-encrypt=mutual; keydata= xsBNBFOMcBYBCACgGjqjoGvbEouQZw/ToiBg9W98AlM2QHV+iNHsEs7kxWhKMjrioyspZKOB ycWxw3ie3j9uvg9EOB3aN4xiTv4qbnGiTr3oJhkB1gsb6ToJQZ8uxGq2kaV2KL9650I1SJve dYm8Of8Zd621lSmoKOwlNClALZNew72NjJLEzTalU1OdT7/i1TXkH09XSSI8mEQ/ouNcMvIJ NwQpd369y9bfIhWUiVXEK7MlRgUG6MvIj6Y3Am/BBLUVbDa4+gmzDC9ezlZkTZG2t14zWPvx XP3FAp2pkW0xqG7/377qptDmrk42GlSKN4z76ELnLxussxc7I2hx18NUcbP8+uty4bMxABEB AAHNHkp1ZXJnZW4gR3Jvc3MgPGpncm9zc0BzdXNlLmRlPsLAeQQTAQIAIwUCU4xw6wIbAwcL CQgHAwIBBhUIAgkKCwQWAgMBAh4BAheAAAoJELDendYovxMvi4UH/Ri+OXlObzqMANruTd4N zmVBAZgx1VW6jLc8JZjQuJPSsd/a+bNr3BZeLV6lu4Pf1Yl2Log129EX1KWYiFFvPbIiq5M5 kOXTO8Eas4CaScCvAZ9jCMQCgK3pFqYgirwTgfwnPtxFxO/F3ZcS8jovza5khkSKL9JGq8Nk czDTruQ/oy0WUHdUr9uwEfiD9yPFOGqp4S6cISuzBMvaAiC5YGdUGXuPZKXLpnGSjkZswUzY d9BVSitRL5ldsQCg6GhDoEAeIhUC4SQnT9SOWkoDOSFRXZ+7+WIBGLiWMd+yKDdRG5RyP/8f 3tgGiB6cyuYfPDRGsELGjUaTUq3H2xZgIPfOwE0EU4xwFgEIAMsx+gDjgzAY4H1hPVXgoLK8 B93sTQFN9oC6tsb46VpxyLPfJ3T1A6Z6MVkLoCejKTJ3K9MUsBZhxIJ0hIyvzwI6aYJsnOew cCiCN7FeKJ/oA1RSUemPGUcIJwQuZlTOiY0OcQ5PFkV5YxMUX1F/aTYXROXgTmSaw0aC1Jpo w7Ss1mg4SIP/tR88/d1+HwkJDVW1RSxC1PWzGizwRv8eauImGdpNnseneO2BNWRXTJumAWDD pYxpGSsGHXuZXTPZqOOZpsHtInFyi5KRHSFyk2Xigzvh3b9WqhbgHHHE4PUVw0I5sIQt8hJq 5nH5dPqz4ITtCL9zjiJsExHuHKN3NZsAEQEAAcLAXwQYAQIACQUCU4xwFgIbDAAKCRCw3p3W KL8TL0P4B/9YWver5uD/y/m0KScK2f3Z3mXJhME23vGBbMNlfwbr+meDMrJZ950CuWWnQ+d+ Ahe0w1X7e3wuLVODzjcReQ/v7b4JD3wwHxe+88tgB9byc0NXzlPJWBaWV01yB2/uefVKryAf AHYEd0gCRhx7eESgNBe3+YqWAQawunMlycsqKa09dBDL1PFRosF708ic9346GLHRc6Vj5SRA UTHnQqLetIOXZm3a2eQ1gpQK9MmruO86Vo93p39bS1mqnLLspVrL4rhoyhsOyh0Hd28QCzpJ wKeHTd0MAWAirmewHXWPco8p1Wg+V+5xfZzuQY0f4tQxvOpXpt4gQ1817GQ5/Ed/wsDtBBgB CAAgFiEEhRJncuj2BJSl0Jf3sN6d1ii/Ey8FAlrd8NACGwIAgQkQsN6d1ii/Ey92IAQZFggA HRYhBFMtsHpB9jjzHji4HoBcYbtP2GO+BQJa3fDQAAoJEIBcYbtP2GO+TYsA/30H/0V6cr/W V+J/FCayg6uNtm3MJLo4rE+o4sdpjjsGAQCooqffpgA+luTT13YZNV62hAnCLKXH9n3+ZAgJ RtAyDWk1B/0SMDVs1wxufMkKC3Q/1D3BYIvBlrTVKdBYXPxngcRoqV2J77lscEvkLNUGsu/z W2pf7+P3mWWlrPMJdlbax00vevyBeqtqNKjHstHatgMZ2W0CFC4hJ3YEetuRBURYPiGzuJXU pAd7a7BdsqWC4o+GTm5tnGrCyD+4gfDSpkOT53S/GNO07YkPkm/8J4OBoFfgSaCnQ1izwgJQ jIpcG2fPCI2/hxf2oqXPYbKr1v4Z1wthmoyUgGN0LPTIm+B5vdY82wI5qe9uN6UOGyTH2B3p hRQUWqCwu2sqkI3LLbTdrnyDZaixT2T0f4tyF5Lfs+Ha8xVMhIyzNb1byDI5FKCb
- Cc: netdev@xxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, xen-devel@xxxxxxxxxxxxxxxxxxxx
- Delivery-date: Fri, 07 Sep 2018 11:30:55 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
- Openpgp: preference=signencrypt
On 07/09/18 13:06, Jiri Slaby wrote:
> On 08/24/2018, 04:26 PM, Boris Ostrovsky wrote:
>> On 08/24/2018 07:26 AM, Juergen Gross wrote:
>>> On 24/08/18 13:12, Jiri Slaby wrote:
>>>> On 07/30/2018, 10:18 AM, Xiao Liang wrote:
>>>>> On 07/29/2018 11:30 PM, David Miller wrote:
>>>>>> From: Xiao Liang <xiliang@xxxxxxxxxx>
>>>>>> Date: Fri, 27 Jul 2018 17:56:08 +0800
>>>>>>
>>>>>>> @@ -1330,6 +1331,11 @@ static struct net_device
>>>>>>> *xennet_create_dev(struct xenbus_device *dev)
>>>>>>> netif_carrier_off(netdev);
>>>>>>> xenbus_switch_state(dev, XenbusStateInitialising);
>>>>>>> + wait_event(module_load_q,
>>>>>>> + xenbus_read_driver_state(dev->otherend) !=
>>>>>>> + XenbusStateClosed &&
>>>>>>> + xenbus_read_driver_state(dev->otherend) !=
>>>>>>> + XenbusStateUnknown);
>>>>>>> return netdev;
>>>>>>> exit:
>>>>>> What performs the wakeups that will trigger for this sleep site?
>>>>> In my understanding, backend leaving closed/unknow state can trigger the
>>>>> wakeups. I mean to make sure both sides are ready for creating connection.
>>>> While backporting this to 4.12, I was surprised by the commit the same
>>>> as Boris and David.
>>>>
>>>> So I assume the explanation is that wake_up_all of module_unload_q in
>>>> netback_changed wakes also all the processes waiting on module_load_q?
>>>> If so, what makes sure that module_unload_q is queued and the process is
>>>> the same as for module_load_q?
>>> How could it? Either the thread is waiting on module_unload_q _or_ on
>>> module_load_q. It can't wait on two queues at the same time.
>>>
>>>> To me, it looks rather error-prone. Unless it is erroneous now, at least
>>>> for future changes. Wouldn't it make sense to wake up module_load_q
>>>> along with module_unload_q in netback_changed? Or drop module_load_q
>>>> completely and use only module_unload_q (i.e. in xennet_create_dev too)?
>>> To me this looks just wrong. A thread waiting on module_load_q won't be
>>> woken up again.
>>>
>>> I'd drop module_load_q in favor of module_unload_q.
>>
>>
>> Yes, use single queue, but rename it to something more neutral. module_wq?
>
> Can somebody who is actually using the module fix this, please?
Already at it.
Juergen
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