linux-kernel - Re: [PATCH] Drivers: hv: util: on deinit, don't wait the release event, if we shouldn't

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Date:   Tue, 28 Feb 2017 14:06:32 +0100
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Dexuan Cui <decui@...rosoft.com>
Cc:     Stephen Hemminger <sthemmin@...rosoft.com>,
        "gregkh\@linuxfoundation.org" <gregkh@...uxfoundation.org>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        "driverdev-devel\@linuxdriverproject.org" 
        <driverdev-devel@...uxdriverproject.org>,
        "Alex Ng \(LIS\)" <alexng@...rosoft.com>,
        "linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Drivers: hv: util: on deinit, don't wait the release event, if we shouldn't

Dexuan Cui <decui@...rosoft.com> writes:

>> From: devel [...] On Behalf Of Dexuan Cui
>> > > --- a/drivers/hv/hv_utils_transport.h
>> > > +++ b/drivers/hv/hv_utils_transport.h
>> > > @@ -32,6 +32,7 @@ struct hvutil_transport {
>> > >     int mode;                           /* hvutil_transport_mode */
>> > >     struct file_operations fops;        /* file operations */
>> > >     struct miscdevice mdev;             /* misc device */
>> > > +   bool   dev_opened;                  /* Is the device opened? */
>> > >     struct cb_id cn_id;                 /* CN_*_IDX/CN_*_VAL */
>> > >     struct list_head list;              /* hvt_list */
>> > >     int (*on_msg)(void *, int);         /* callback on new user message */
>> >
>> > I think we can get away without introducing this new flag, e.g. if we
>> > replace release_event with an atomic which will hold the state
>> > (open/closed). This will also elimenate possible races above. I can try
>> > prototyping a patch if you want me to.
>> > --
>> >   Vitaly
>> 
>> Thanks for offering the help! Please do. :-)
>
> BTW, IMO I found another potential issue:
> In hvt_op_open -> hvt_reset -> kvp_on_reset(), I think we should call
> init_completion() instead of complete()?
>

To me it looks like we can do better with something different from
struct completion, I'll take a look later today.

-- 
  Vitaly