linux-kernel - Re: [PATCH v2] firmware: fix sending -ERESTARTSYS due to signal on fallback

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Date:   Thu, 8 Jun 2017 18:14:25 -0700
From:   Andy Lutomirski <luto@...nel.org>
To:     Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:     Andy Lutomirski <luto@...nel.org>,
        "Luis R. Rodriguez" <mcgrof@...nel.org>,
        "Theodore Ts'o" <tytso@....edu>, Alan Cox <alan@...ux.intel.com>,
        Linux FS Devel <linux-fsdevel@...r.kernel.org>,
        Stephen Boyd <stephen.boyd@...aro.org>,
        "Li, Yi" <yi1.li@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Jonathan Corbet <corbet@....net>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        "Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        "Fuzzey, Martin" <mfuzzey@...keon.com>,
        Linux API <linux-api@...r.kernel.org>,
        Daniel Wagner <wagi@...om.org>,
        David Woodhouse <dwmw2@...radead.org>,
        jewalt@...innovations.com, rafal@...ecki.pl,
        Arend Van Spriel <arend.vanspriel@...adcom.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        atull@...nsource.altera.com,
        Moritz Fischer <moritz.fischer@...us.com>,
        Petr Mladek <pmladek@...e.com>,
        Johannes Berg <johannes.berg@...el.com>,
        Emmanuel Grumbach <emmanuel.grumbach@...el.com>,
        Luca Coelho <luciano.coelho@...el.com>,
        Kalle Valo <kvalo@...eaurora.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Kees Cook <keescook@...omium.org>,
        AKASHI Takahiro <takahiro.akashi@...aro.org>,
        David Howells <dhowells@...hat.com>,
        Peter Jones <pjones@...hat.com>,
        Hans de G oede <hdegoede@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] firmware: fix sending -ERESTARTSYS due to signal on fallback

On Tue, Jun 6, 2017 at 11:25 PM, Dmitry Torokhov
<dmitry.torokhov@...il.com> wrote:
> On Tue, Jun 06, 2017 at 09:56:47PM -0700, Andy Lutomirski wrote:
>> On Tue, Jun 6, 2017 at 5:22 PM, Luis R. Rodriguez <mcgrof@...nel.org> wrote:
>> > On Tue, Jun 06, 2017 at 06:11:51PM -0400, Theodore Ts'o wrote:
>> >> On Tue, Jun 06, 2017 at 06:47:34PM +0200, Luis R. Rodriguez wrote:
>> >> > On Tue, Jun 06, 2017 at 03:53:16PM +0100, Alan Cox wrote:
>> >
>> > We rely on swait, and swait right now only uses -ERESTARTSYS. Are
>> > you saying we could mask out -ERESTARTSYS and map it to -ERESTARTNOINTR
>> > or -ERESTARTNOHAND if we see fit for some future functionality / need ?
>>
>> I think that has essentially nothing to do with swait.  User code does
>> some syscall.  That syscall triggers a firmware load.  The caller gets
>> a signal.  If you're going to let firmware load get interrupted, you
>> need to consider what the syscall is.
>
> I think it is way too complicated and I do not think driver writers will
> stand a chance of implementing this correctly, given that often firmware
> load might be triggered indirectly and by multitude of syscalls.
>

That's what I meant, but I said it unclearly.  I meant that, if we're
going to start allowing interruption, we would need to audit all the
callers.  Ugh.

I suppose we could have request_firmware_interruptable(), but that
seems like it's barely worth it.

--Andy