linux-kernel - Re: [PATCH v2 1/1] ACPI: scan: Use unique number for instance

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Message-ID: <YFT5woqIyNtypwXX@smile.fi.intel.com>
Date:   Fri, 19 Mar 2021 21:21:38 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "open list:ACPI COMPONENT ARCHITECTURE (ACPICA)" <devel@...ica.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>,
        Robert Moore <robert.moore@...el.com>,
        Erik Kaneda <erik.kaneda@...el.com>
Subject: Re: [PATCH v2 1/1] ACPI: scan: Use unique number for instance_no

On Fri, Mar 19, 2021 at 07:51:00PM +0100, Rafael J. Wysocki wrote:
> On Fri, Mar 19, 2021 at 7:33 PM Andy Shevchenko
> <andriy.shevchenko@...ux.intel.com> wrote:
> >
> > Current mechanism of incrementing and decrementing plain integer
> > to get a next free instance_no when creating an ACPI device is buggy.
> >
> > The simple integer and operations line increment and decrement
> > on top of it can't cover the possible gaps during run time. The
> > arbitrary instantiation and elimination of the devices is racy
> 
> But it isn't racy AFAICS.  It always happens under acpi_device_lock().

Hmm.. indeed. I sent a v3 with the commit message based on your proposal.


> > and after a couple of iterations with unequal amount of devices
> > being added and removed we may reproduce a bug:

-- 
With Best Regards,
Andy Shevchenko