From: Dave.Martin@arm.com (Dave P Martin)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH] serial/amba-pl011: Disable interrupts around TX softirq
Date: Mon, 8 Jun 2015 12:34:11 +0100 [thread overview]
Message-ID: <20150608113406.GA3654@e103592.cambridge.arm.com> (raw)
In-Reply-To: <55756FC5.5000801@arm.com>
On Mon, Jun 08, 2015 at 11:34:45AM +0100, Robin Murphy wrote:
> On 05/06/15 19:03, Robin Murphy wrote:
> > On 05/06/15 15:07, Dave P Martin wrote:
> >> pl011_tx_softirq() currently uses spin_{,un}lock(), which are not
> >> sufficient to inhibit pl011_int() from being triggered by a local
> >> IRQ and trying to re-take the same lock. This can lead to
> >> deadlocks.
> >>
> >> This patch uses the _irq() locking variants instead to ensure that
> >> pl011_int() handling for a given port is deferred until any
> >> pl011_tx_softirq() work for that port is complete.
> >>
> >> Signed-off-by: Dave Martin <Dave.Martin@arm.com>
> >> ---
> >>
> >> Another candidate for v4.1 if possible (sorry!) -- I thought this change
> >> was already in, but it went astray when I was refactoring.
> >>
> >> This patch conflicts with tty-next like the previous patch, since it
> >> fixes code that is removed by tty-next. The correct resolution for
> >> the resulting merge conflict is to keep the code from tty-next.
> >>
> >>
> >> I am not 100% certain yet whether some rare deadlocks that Robin is
> >> seeing are caused by this issue, or whether this patch fixes them --
> >> he's testing atm.
> >
> > FWIW, I've been running Juno in a startup/shutdown loop with a very
> > noisy systemd all afternoon and haven't hit a problem yet with this
> > patch applied. Testing without this patch yesterday I saw 3 or 4 lockdep
> > splats in about the same amount of time. I'll leave it going over the
> > weekend just to make sure, though.
>
> Having still seen nothing over several hundred more reboot cycles, I'm
> satisfied that the irq vs. softirq race explains the deadlock and that
> this patch fixes it, so;
>
> Tested-by: Robin Murphy <robin.murphy@arm.com>
Thanks for this
Cheers
---Dave
WARNING: multiple messages have this Message-ID (diff)
From: Dave P Martin <Dave.Martin@arm.com>
To: Robin Murphy <Robin.Murphy@arm.com>
Cc: "Russell King" <linux@arm.linux.org.uk>,
"Jakub Kiciński" <moorray3@wp.pl>,
"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
"Andrew Jackson" <Andrew.Jackson@arm.com>,
"Graeme Gregory" <gg@slimlogic.co.uk>,
"linux-serial@vger.kernel.org" <linux-serial@vger.kernel.org>,
"Andre Przywara" <Andre.Przywara@arm.com>,
"popcorn mix" <popcornmix@gmail.com>,
"Jorge Ramirez-Ortiz" <jorge.ramirez-ortiz@linaro.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH] serial/amba-pl011: Disable interrupts around TX softirq
Date: Mon, 8 Jun 2015 12:34:11 +0100 [thread overview]
Message-ID: <20150608113406.GA3654@e103592.cambridge.arm.com> (raw)
In-Reply-To: <55756FC5.5000801@arm.com>
On Mon, Jun 08, 2015 at 11:34:45AM +0100, Robin Murphy wrote:
> On 05/06/15 19:03, Robin Murphy wrote:
> > On 05/06/15 15:07, Dave P Martin wrote:
> >> pl011_tx_softirq() currently uses spin_{,un}lock(), which are not
> >> sufficient to inhibit pl011_int() from being triggered by a local
> >> IRQ and trying to re-take the same lock. This can lead to
> >> deadlocks.
> >>
> >> This patch uses the _irq() locking variants instead to ensure that
> >> pl011_int() handling for a given port is deferred until any
> >> pl011_tx_softirq() work for that port is complete.
> >>
> >> Signed-off-by: Dave Martin <Dave.Martin@arm.com>
> >> ---
> >>
> >> Another candidate for v4.1 if possible (sorry!) -- I thought this change
> >> was already in, but it went astray when I was refactoring.
> >>
> >> This patch conflicts with tty-next like the previous patch, since it
> >> fixes code that is removed by tty-next. The correct resolution for
> >> the resulting merge conflict is to keep the code from tty-next.
> >>
> >>
> >> I am not 100% certain yet whether some rare deadlocks that Robin is
> >> seeing are caused by this issue, or whether this patch fixes them --
> >> he's testing atm.
> >
> > FWIW, I've been running Juno in a startup/shutdown loop with a very
> > noisy systemd all afternoon and haven't hit a problem yet with this
> > patch applied. Testing without this patch yesterday I saw 3 or 4 lockdep
> > splats in about the same amount of time. I'll leave it going over the
> > weekend just to make sure, though.
>
> Having still seen nothing over several hundred more reboot cycles, I'm
> satisfied that the irq vs. softirq race explains the deadlock and that
> this patch fixes it, so;
>
> Tested-by: Robin Murphy <robin.murphy@arm.com>
Thanks for this
Cheers
---Dave
next prev parent reply other threads:[~2015-06-08 11:34 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-05 14:07 [PATCH] serial/amba-pl011: Disable interrupts around TX softirq Dave Martin
2015-06-05 14:07 ` Dave Martin
2015-06-05 18:03 ` Robin Murphy
2015-06-05 18:03 ` Robin Murphy
2015-06-08 10:34 ` Robin Murphy
2015-06-08 10:34 ` Robin Murphy
2015-06-08 11:34 ` Dave P Martin [this message]
2015-06-08 11:34 ` Dave P Martin
2015-06-13 0:39 ` Greg Kroah-Hartman
2015-06-13 0:39 ` Greg Kroah-Hartman
2015-06-15 10:53 ` Dave P Martin
2015-06-15 10:53 ` Dave P Martin
2015-06-15 11:09 ` Andre Przywara
2015-06-15 11:09 ` Andre Przywara
2015-06-15 14:03 ` Dave Martin
2015-06-15 14:03 ` Dave Martin
-- strict thread matches above, loose matches on Subject: below --
2015-06-18 13:54 Dave Martin
2015-06-18 13:54 ` Dave Martin
2015-06-20 9:09 ` Stefan Wahren
2015-06-20 9:09 ` Stefan Wahren
2015-06-20 9:09 ` Stefan Wahren
2015-06-23 11:13 ` Dave P Martin
2015-06-23 11:13 ` Dave P Martin
2015-07-09 10:57 Dave Martin
2015-07-09 10:57 ` Dave Martin
2015-07-23 22:05 ` Greg Kroah-Hartman
2015-07-23 22:05 ` Greg Kroah-Hartman
2015-07-24 9:56 ` Dave Martin
2015-07-24 9:56 ` Dave Martin
2015-07-24 15:15 ` Greg Kroah-Hartman
2015-07-24 15:15 ` Greg Kroah-Hartman
2015-07-24 16:46 ` Dave Martin
2015-07-24 16:46 ` Dave Martin
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