linux-kernel - Re: [PATCH 2/4] swait: add the missing killable swaits

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Date:   Thu, 29 Jun 2017 16:06:22 -0700
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     "Luis R. Rodriguez" <mcgrof@...nel.org>
Cc:     Nicolas Broeking <nbroeking@...com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Davidlohr Bueso <dave@...olabs.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Greg KH <gregkh@...uxfoundation.org>,
        Martin Fuzzey <mfuzzey@...keon.com>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        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>,
        "Li, Yi" <yi1.li@...ux.intel.com>, atull@...nel.org,
        Moritz Fischer <moritz.fischer@...us.com>,
        Petr Mladek <pmladek@...e.com>,
        Johannes Berg <johannes.berg@...el.com>,
        Emmanuel Grumbach <emmanuel.grumbach@...el.com>,
        "Coelho, Luciano" <luciano.coelho@...el.com>,
        Kalle Valo <kvalo@...eaurora.org>,
        Andrew Lutomirski <luto@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        "AKASHI, Takahiro" <takahiro.akashi@...aro.org>,
        David Howells <dhowells@...hat.com>,
        Peter Jones <pjones@...hat.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Alan Cox <alan@...ux.intel.com>,
        "Theodore Ts'o" <tytso@....edu>,
        Michael Kerrisk <mtk.manpages@...il.com>,
        Paul Gortmaker <paul.gortmaker@...driver.com>,
        Marcelo Tosatti <mtosatti@...hat.com>,
        Matthew Wilcox <mawilcox@...rosoft.com>,
        Linux API <linux-api@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "stable # 4 . 6" <stable@...r.kernel.org>
Subject: Re: [PATCH 2/4] swait: add the missing killable swaits

On Thu, 29 Jun 2017 16:00:32 -0700, Luis R. Rodriguez wrote:
> On Thu, Jun 29, 2017 at 3:53 PM, Jakub Kicinski
> <jakub.kicinski@...ronome.com> wrote:
> > On Fri, 30 Jun 2017 00:50:03 +0200, Luis R. Rodriguez wrote:  
> >> On Thu, Jun 29, 2017 at 01:58:22PM -0700, Jakub Kicinski wrote:  
> >> > On Thu, 29 Jun 2017 21:44:55 +0200, Luis R. Rodriguez wrote:  
> >> > > > Since this swake_up() --> swake_up_all() reportedly *fixed* the one wake up
> >> > > > issue it would seem this does queue [0]. That said, I don't see any simple tests
> >> > > > tools/testing/selftests/swait but then again we don't have test for regular
> >> > > > waits either...
> >> > > >
> >> > > > [0] https://bugzilla.kernel.org/show_bug.cgi?id=195477  
> >> > >
> >> > > I should also note that the swake_up_all() should have only helped in cases where
> >> > > 3 cards were used, as if only 2 were used that should have been covered by just
> >> > > the swake_up(). Unless of course I hear otherwise by the reporter, Nicolas or
> >> > > from Jakub.  
> >> >
> >> > I was hitting this with 2 cards.  
> >>
> >> Thanks!
> >>
> >> Thing is I'm not convinced the issue with 2 cards was the swake_up() Vs
> >> swake_up_all() in this case though. Let's recall also the missing wake up on
> >> errors! And the fact that netronome has optional firmware, which naturally can
> >> fail.
> >>
> >> So could the issue with 2 cards instead of the miss of a wake up on error due
> >> to batched requests ? If so then that still would not put blame on the
> >> swake_up()!  
> >
> > Sorry, that was during manual tests.  I had the driver request the
> > firmware with _nowait() without an uevent,  
> 
> Can you provide the output of
> 
> grep  CONFIG_FW_LOADER_USER_HELPER .config
> 
> I'd like to see if CONFIG_FW_LOADER_USER_HELPER_FALLBACK was disabled.
> Not to be confused with the CONFIG_FW_LOADER_USER_HELPER.
> 
> When the uevent is not set its also known as "a custom fallback
> mechanism" and by default that has set a timeout of
> MAX_SCHEDULE_TIMEOUT, which means that even if the direct filesystem
> lookup failed the fallback mechanism would be used and just sit and
> wait for what seems to be forever until user input was provided.

FWIW

CONFIG_FW_LOADER=y
CONFIG_FW_LOADER_USER_HELPER=y
CONFIG_FW_LOADER_USER_HELPER_FALLBACK=y
# CONFIG_FW_CFG_SYSFS is not set

> > and then after I manually
> > wrote -1 to loading only one would get woken up.  
> 
> Great, this helps, so for those not familiar with the firmware sysfs
> fallback mechanism:
> 
> The relevant values one could use are:
> 
> 1: Start a load, discarding any previous partial load.
> 0: Conclude the load and hand the data to the driver code.
> -1: Conclude the load with an error and discard any written data.
> 
> So you are triggering a failure. And indeed I expect the patch I just
> provided to be the one to fix your issue with 2 cards.

Cool, thanks.