Message-ID: <1496760796.5682.48.camel@linux.intel.com>
Subject: Re: [PATCH v2] firmware: fix sending -ERESTARTSYS due to signal on
 fallback
From: Alan Cox <alan@linux.intel.com>
To: "Luis R. Rodriguez" <mcgrof@kernel.org>,
        Dmitry Torokhov <dmitry.torokhov@gmail.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Jonathan Corbet <corbet@lwn.net>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com>,
        Andy Lutomirski <luto@kernel.org>,
        Greg KH <gregkh@linuxfoundation.org>
Cc: "Fuzzey, Martin" <mfuzzey@parkeon.com>,
        Linux API <linux-api@vger.kernel.org>, Daniel Wagner <wagi@monom.org>,
        David Woodhouse <dwmw2@infradead.org>, jewalt@lgsinnovations.com,
        rafal@milecki.pl, Arend Van Spriel <arend.vanspriel@broadcom.com>,
        "Rafael J. Wysocki" <rjw@rjwysocki.net>,
        "Li, Yi" <yi1.li@linux.intel.com>, atull@opensource.altera.com,
        Moritz Fischer <moritz.fischer@ettus.com>,
        Petr Mladek <pmladek@suse.com>,
        Johannes Berg <johannes.berg@intel.com>,
        Emmanuel Grumbach <emmanuel.grumbach@intel.com>,
        Luca Coelho <luciano.coelho@intel.com>,
        Kalle Valo <kvalo@codeaurora.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Kees Cook <keescook@chromium.org>,
        AKASHI Takahiro <takahiro.akashi@linaro.org>,
        David Howells <dhowells@redhat.com>, Peter Jones <pjones@redhat.com>,
        Hans de G oede <hdegoede@redhat.com>, "Ted Ts'o" <tytso@mit.edu>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Date: Tue, 06 Jun 2017 15:53:16 +0100
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> "Unix tradition (and thus almost all applications) believe file store
> writes to
> be non signal interruptible. It would not be safe or practical to
> change that
> guarantee."

Yep everyone codes

	write(disk_file, "foo", 3);

not while(..) blah around it.

> For these two reasons then it would seem best we do two things
> actually:
> 
> 1) return -EINTR instead of -EAGAIN when we detect
> swait_event_interruptible_timeout()
> got interrupted by a signal (it returns -ERESTARTSYS)
> 2) Do as you note below and add wait_event_killable_timeout()

Pedantic detail that I don't think affects you

If you have completed a part of the I/O then you should return the byte
processed count not EINTR, but -1,EINTR if no progress was made.

Alan