linux-kernel - Re: [PATCH v1] ACPI / scan: Acquire device_hotplug_lock in acpi_scan

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Message-ID: <CAJZ5v0iBntT1c7gKkXG-RJpabZne2n-Afq40GKeA6-tUViVZuQ@mail.gmail.com>
Date:   Thu, 25 Jul 2019 11:22:46 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Oscar Salvador <osalvador@...e.de>
Cc:     David Hildenbrand <david@...hat.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.com>
Subject: Re: [PATCH v1] ACPI / scan: Acquire device_hotplug_lock in acpi_scan_init()

On Thu, Jul 25, 2019 at 11:18 AM Oscar Salvador <osalvador@...e.de> wrote:
>
> On Wed, Jul 24, 2019 at 04:30:17PM +0200, David Hildenbrand wrote:
> > We end up calling __add_memory() without the device hotplug lock held.
> > (I used a local patch to assert in __add_memory() that the
> >  device_hotplug_lock is held - I might upstream that as well soon)
> >
> > [   26.771684]        create_memory_block_devices+0xa4/0x140
> > [   26.772952]        add_memory_resource+0xde/0x200
> > [   26.773987]        __add_memory+0x6e/0xa0
> > [   26.775161]        acpi_memory_device_add+0x149/0x2b0
> > [   26.776263]        acpi_bus_attach+0xf1/0x1f0
> > [   26.777247]        acpi_bus_attach+0x66/0x1f0
> > [   26.778268]        acpi_bus_attach+0x66/0x1f0
> > [   26.779073]        acpi_bus_attach+0x66/0x1f0
> > [   26.780143]        acpi_bus_scan+0x3e/0x90
> > [   26.780844]        acpi_scan_init+0x109/0x257
> > [   26.781638]        acpi_init+0x2ab/0x30d
> > [   26.782248]        do_one_initcall+0x58/0x2cf
> > [   26.783181]        kernel_init_freeable+0x1bd/0x247
> > [   26.784345]        kernel_init+0x5/0xf1
> > [   26.785314]        ret_from_fork+0x3a/0x50
> >
> > So perform the locking just like in acpi_device_hotplug().
> >
> > Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>
> > Cc: Len Brown <lenb@...nel.org
> > Cc: Andrew Morton <akpm@...ux-foundation.org>
> > Cc: Oscar Salvador <osalvador@...e.de>
> > Cc: Michal Hocko <mhocko@...e.com>
> > Signed-off-by: David Hildenbrand <david@...hat.com>
>
> Given that that call comes from a __init function, so while booting, I wonder
> how bad it is.

Yes, it probably does not matter.

> Anyway, let us be consistent:

Right.