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From: Russell King - ARM Linux <linux@arm.linux.org.uk>
To: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Marc Zyngier <marc.zyngier@arm.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Viresh Kumar <viresh.kumar@linaro.org>,
	"linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>,
	"Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	linux-next@vger.kernel.org,
	"linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>,
	Guenter Roeck <linux@roeck-us.net>
Subject: Re: Crashes in arm qemu emulations due to 'cpufreq: governor: Replace timers with utilization ...'
Date: Mon, 15 Feb 2016 19:07:00 +0000	[thread overview]
Message-ID: <20160215190700.GN10826@n2100.arm.linux.org.uk> (raw)
In-Reply-To: <CAJZ5v0gfOVyoWeee5jg7NxLFm-xwdA6-sPQV+cJ=NWJOV-wYzg@mail.gmail.com>

On Mon, Feb 15, 2016 at 07:54:26PM +0100, Rafael J. Wysocki wrote:
> On Mon, Feb 15, 2016 at 7:49 PM, Marc Zyngier <marc.zyngier@arm.com> wrote:
> > Given that OMAP3 is a UP system, there is zero chance that it has
> > registered the magic hook that delivers IPIs (its interrupt controller
> > is not even capable of doing so).
> >
> > I don't really know the context, but IPIs on a UP system seem at best odd.
> 
> That would explain it, thanks.
> 
> So it looks like we should always use irq_work_queue() on UP even if
> CONFIG_SMP is set, shouldn't we?

irq_work_queue_on() doesn't check whether 'cpu' is the CPU that we're
running on.  This is a problem where we want to be able to run a kernel
built for SMP on a UP system.

I guess the question is whether irq_work_queue_on() is buggy, or whether
our implementation of arch_send_call_function_single_ipi() is buggy.
Should arch_send_call_function_single_ipi() do something on UP systems,
if so what?

We don't have IPIs on UP systems, so we can't raise any interrupts.
So, should we call generic_smp_call_function_interrupt() directly
from it?

Some clues would be good...

-- 
RMK's Patch system: http://www.arm.linux.org.uk/developer/patches/
FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
according to speedtest.net.

WARNING: multiple messages have this Message-ID (diff)
From: linux@arm.linux.org.uk (Russell King - ARM Linux)
To: linux-arm-kernel@lists.infradead.org
Subject: Crashes in arm qemu emulations due to 'cpufreq: governor: Replace timers with utilization ...'
Date: Mon, 15 Feb 2016 19:07:00 +0000	[thread overview]
Message-ID: <20160215190700.GN10826@n2100.arm.linux.org.uk> (raw)
In-Reply-To: <CAJZ5v0gfOVyoWeee5jg7NxLFm-xwdA6-sPQV+cJ=NWJOV-wYzg@mail.gmail.com>

On Mon, Feb 15, 2016 at 07:54:26PM +0100, Rafael J. Wysocki wrote:
> On Mon, Feb 15, 2016 at 7:49 PM, Marc Zyngier <marc.zyngier@arm.com> wrote:
> > Given that OMAP3 is a UP system, there is zero chance that it has
> > registered the magic hook that delivers IPIs (its interrupt controller
> > is not even capable of doing so).
> >
> > I don't really know the context, but IPIs on a UP system seem at best odd.
> 
> That would explain it, thanks.
> 
> So it looks like we should always use irq_work_queue() on UP even if
> CONFIG_SMP is set, shouldn't we?

irq_work_queue_on() doesn't check whether 'cpu' is the CPU that we're
running on.  This is a problem where we want to be able to run a kernel
built for SMP on a UP system.

I guess the question is whether irq_work_queue_on() is buggy, or whether
our implementation of arch_send_call_function_single_ipi() is buggy.
Should arch_send_call_function_single_ipi() do something on UP systems,
if so what?

We don't have IPIs on UP systems, so we can't raise any interrupts.
So, should we call generic_smp_call_function_interrupt() directly
from it?

Some clues would be good...

-- 
RMK's Patch system: http://www.arm.linux.org.uk/developer/patches/
FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
according to speedtest.net.

  parent reply	other threads:[~2016-02-15 19:07 UTC|newest]

Thread overview: 81+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-02-15 17:05 Crashes in arm qemu emulations due to 'cpufreq: governor: Replace timers with utilization ...' Guenter Roeck
2016-02-15 17:05 ` Guenter Roeck
2016-02-15 18:41 ` Rafael J. Wysocki
2016-02-15 18:41   ` Rafael J. Wysocki
2016-02-15 18:41   ` Rafael J. Wysocki
2016-02-15 18:49   ` Rafael J. Wysocki
2016-02-15 18:49     ` Rafael J. Wysocki
2016-02-15 18:49     ` Rafael J. Wysocki
2016-02-15 18:49   ` Marc Zyngier
2016-02-15 18:49     ` Marc Zyngier
2016-02-15 18:49     ` Marc Zyngier
2016-02-15 18:54     ` Rafael J. Wysocki
2016-02-15 18:54       ` Rafael J. Wysocki
2016-02-15 18:54       ` Rafael J. Wysocki
2016-02-15 19:03       ` Marc Zyngier
2016-02-15 19:03         ` Marc Zyngier
2016-02-15 19:03         ` Marc Zyngier
2016-02-15 19:12         ` Rafael J. Wysocki
2016-02-15 19:12           ` Rafael J. Wysocki
2016-02-15 19:12           ` Rafael J. Wysocki
2016-02-15 19:28           ` Rafael J. Wysocki
2016-02-15 19:28             ` Rafael J. Wysocki
2016-02-15 19:28             ` Rafael J. Wysocki
2016-02-15 19:42             ` Tony Lindgren
2016-02-15 19:42               ` Tony Lindgren
2016-02-15 19:42               ` Tony Lindgren
2016-02-15 19:46               ` Guenter Roeck
2016-02-15 19:46                 ` Guenter Roeck
2016-02-15 19:46                 ` Guenter Roeck
2016-02-15 19:57                 ` Tony Lindgren
2016-02-15 19:57                   ` Tony Lindgren
2016-02-15 19:57                   ` Tony Lindgren
2016-02-15 19:23         ` Russell King - ARM Linux
2016-02-15 19:23           ` Russell King - ARM Linux
2016-02-15 19:23           ` Russell King - ARM Linux
2016-02-15 20:41           ` Rafael J. Wysocki
2016-02-15 20:41             ` Rafael J. Wysocki
2016-02-15 20:41             ` Rafael J. Wysocki
2016-02-15 19:07       ` Russell King - ARM Linux [this message]
2016-02-15 19:07         ` Russell King - ARM Linux
2016-02-15 19:07         ` Russell King - ARM Linux
2016-02-15 19:01   ` Tony Lindgren
2016-02-15 19:01     ` Tony Lindgren
2016-02-15 19:01     ` Tony Lindgren
2016-02-15 19:40     ` Guenter Roeck
2016-02-15 19:40       ` Guenter Roeck
2016-02-15 19:40       ` Guenter Roeck
2016-02-15 19:58       ` Tony Lindgren
2016-02-15 19:58         ` Tony Lindgren
2016-02-15 19:58         ` Tony Lindgren
2016-02-15 20:09         ` Guenter Roeck
2016-02-15 20:09           ` Guenter Roeck
2016-02-15 20:09           ` Guenter Roeck
2016-02-15 20:38           ` Rafael J. Wysocki
2016-02-15 20:38             ` Rafael J. Wysocki
2016-02-15 20:38             ` Rafael J. Wysocki
2016-02-15 20:37         ` Rafael J. Wysocki
2016-02-15 20:37           ` Rafael J. Wysocki
2016-02-15 20:37           ` Rafael J. Wysocki
2016-02-15 21:36           ` Tony Lindgren
2016-02-15 21:36             ` Tony Lindgren
2016-02-15 21:36             ` Tony Lindgren
2016-02-16  1:38             ` Guenter Roeck
2016-02-16  1:38               ` Guenter Roeck
2016-02-16  1:38               ` Guenter Roeck
2016-02-15 19:02   ` Russell King - ARM Linux
2016-02-15 19:02     ` Russell King - ARM Linux
2016-02-15 19:02     ` Russell King - ARM Linux
2016-02-16  1:13   ` Viresh Kumar
2016-02-16  1:13     ` Viresh Kumar
2016-02-16  1:13     ` Viresh Kumar
2016-02-16  1:27     ` Rafael J. Wysocki
2016-02-16  1:27       ` Rafael J. Wysocki
2016-02-16  1:27       ` Rafael J. Wysocki
2016-02-16  1:36       ` Viresh Kumar
2016-02-16  1:36         ` Viresh Kumar
2016-02-16  1:36         ` Viresh Kumar
2016-02-15 22:29 ` Peter Maydell
2016-02-15 22:29   ` Peter Maydell
2016-02-15 23:19   ` Guenter Roeck
2016-02-15 23:19     ` Guenter Roeck

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