linux-kernel - Re: [driver-core PATCH v8 2/9] driver core: Establish order of operations for device_add and device

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Message-ID: <CAPcyv4hrML3SKnFP9UANC-hdTrpnOx4nWX=b-yhLsLuujL5oAA@mail.gmail.com>
Date:   Mon, 10 Dec 2018 13:23:48 -0800
From:   Dan Williams <dan.j.williams@...el.com>
To:     alexander.h.duyck@...ux.intel.com
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        "Luis R. Rodriguez" <mcgrof@...nel.org>,
        linux-nvdimm <linux-nvdimm@...ts.01.org>,
        Tejun Heo <tj@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux-pm mailing list <linux-pm@...r.kernel.org>,
        jiangshanlai@...il.com, "Rafael J. Wysocki" <rafael@...nel.org>,
        "Brown, Len" <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
        zwisler@...nel.org, Dave Jiang <dave.jiang@...el.com>,
        bvanassche@....org
Subject: Re: [driver-core PATCH v8 2/9] driver core: Establish order of
 operations for device_add and device_del via bitflag

On Mon, Dec 10, 2018 at 1:15 PM Dan Williams <dan.j.williams@...el.com> wrote:
>
> On Mon, Dec 10, 2018 at 12:58 PM Alexander Duyck
> <alexander.h.duyck@...ux.intel.com> wrote:
[..]
> > Also the context for the two functions seems to be a bit different. In
> > the case of __device_attach_driver the device_lock is already held. In
> > __driver_attach the lock on the device isn't taken until after a match
> > has been found.
>
> Yes, I was only pattern matching when looking at the context of where
> dev->dead is checked in __driver_attach() and wondering why it was
> checked outside of __device_attach_driver()

...and now I realize the bigger point of your concern, we need to
check dev->dead after acquiring the device_lock otherwise the race is
back. We can defer that consolidation, but the larger concern of
making it internal to __device_attach_driver() still stands.