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    SubjectRe: [Xen-devel] Re: xen: IPI interrupts not resumed early enough on suspend/resume
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    On Fri, 2011-10-14 at 14:23 +0100, Ian Campbell wrote:
    > Ping? The original issue has made it into longterm-2.6.32.y and then
    > onto Debian (bug #644604) so people keep asking me about it...

    Sorry, the previous version had a warning in it (was missing the return
    type for resume_irqs), fixed up version follows.

    I noticed that the backport to longterm 2.6.32 won't work since syscore
    isn't available back then. I think one approach for the backport would
    be to call irq_pm_syscore_resume() directly from sysdev_resume(), does
    that sound sensible?

    Ian.

    8<------------------------------

    From cac68962d009cd916cc66b4d870630adc49c1e1e Mon Sep 17 00:00:00 2001
    From: Ian Campbell <ian.campbell@citrix.com>
    Date: Mon, 3 Oct 2011 15:37:00 +0100
    Subject: [PATCH] irq: add IRQF_RESUME_EARLY and resume such IRQs earlier in the process
    MIME-Version: 1.0
    Content-Type: text/plain; charset=UTF-8
    Content-Transfer-Encoding: 8bit

    This adds a mechanism to resume selected IRQs during syscore_resume instead of
    dpm_resume_noirq.

    Under Xen we need to resume IRQs associated with IPIs early enough that the
    resched IPI is unmasked and we can therefore schedule ourselves out of the
    stop_machine where the suspend/resume takes place.

    This issue was introduced by 676dc3cf5bc3 "xen: Use IRQF_FORCE_RESUME".

    Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: Rafael J. Wysocki <rjw@sisk.pl>
    Cc: Jeremy Fitzhardinge <jeremy@goop.org>
    Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
    Cc: xen-devel <xen-devel@lists.xensource.com>
    Cc: stable@kernel.org (at least to 2.6.32.y)
    [v2: refactor common code in irq_pm_syscore_resume and resume_device_irqs]
    [v3: resume_irqs returns void, "fixing warning: return type defaults to ‘int’"]
    ---
    drivers/xen/events.c | 2 +-
    include/linux/interrupt.h | 3 ++
    kernel/irq/pm.c | 48 ++++++++++++++++++++++++++++++++++++++------
    3 files changed, 45 insertions(+), 8 deletions(-)

    diff --git a/drivers/xen/events.c b/drivers/xen/events.c
    index 7523719..44490de 100644
    --- a/drivers/xen/events.c
    +++ b/drivers/xen/events.c
    @@ -1021,7 +1021,7 @@ int bind_ipi_to_irqhandler(enum ipi_vector ipi,
    if (irq < 0)
    return irq;

    - irqflags |= IRQF_NO_SUSPEND | IRQF_FORCE_RESUME;
    + irqflags |= IRQF_NO_SUSPEND | IRQF_FORCE_RESUME | IRQF_EARLY_RESUME;
    retval = request_irq(irq, handler, irqflags, devname, dev_id);
    if (retval != 0) {
    unbind_from_irq(irq);
    diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
    index a103732..f51a81b 100644
    --- a/include/linux/interrupt.h
    +++ b/include/linux/interrupt.h
    @@ -59,6 +59,8 @@
    * IRQF_NO_SUSPEND - Do not disable this IRQ during suspend
    * IRQF_FORCE_RESUME - Force enable it on resume even if IRQF_NO_SUSPEND is set
    * IRQF_NO_THREAD - Interrupt cannot be threaded
    + * IRQF_EARLY_RESUME - Resume IRQ early during syscore instead of at device
    + * resume time.
    */
    #define IRQF_DISABLED 0x00000020
    #define IRQF_SAMPLE_RANDOM 0x00000040
    @@ -72,6 +74,7 @@
    #define IRQF_NO_SUSPEND 0x00004000
    #define IRQF_FORCE_RESUME 0x00008000
    #define IRQF_NO_THREAD 0x00010000
    +#define IRQF_EARLY_RESUME 0x00020000

    #define IRQF_TIMER (__IRQF_TIMER | IRQF_NO_SUSPEND | IRQF_NO_THREAD)

    diff --git a/kernel/irq/pm.c b/kernel/irq/pm.c
    index f76fc00..15e53b1 100644
    --- a/kernel/irq/pm.c
    +++ b/kernel/irq/pm.c
    @@ -9,6 +9,7 @@
    #include <linux/irq.h>
    #include <linux/module.h>
    #include <linux/interrupt.h>
    +#include <linux/syscore_ops.h>

    #include "internals.h"

    @@ -39,25 +40,58 @@ void suspend_device_irqs(void)
    }
    EXPORT_SYMBOL_GPL(suspend_device_irqs);

    -/**
    - * resume_device_irqs - enable interrupt lines disabled by suspend_device_irqs()
    - *
    - * Enable all interrupt lines previously disabled by suspend_device_irqs() that
    - * have the IRQS_SUSPENDED flag set.
    - */
    -void resume_device_irqs(void)
    +static void resume_irqs(bool want_early)
    {
    struct irq_desc *desc;
    int irq;

    for_each_irq_desc(irq, desc) {
    unsigned long flags;
    + bool is_early = desc->action &&
    + desc->action->flags & IRQF_EARLY_RESUME;
    +
    + if (is_early != want_early)
    + continue;

    raw_spin_lock_irqsave(&desc->lock, flags);
    __enable_irq(desc, irq, true);
    raw_spin_unlock_irqrestore(&desc->lock, flags);
    }
    }
    +
    +/**
    + * irq_pm_syscore_ops - enable interrupt lines early
    + *
    + * Enable all interrupt lines with %IRQF_EARLY_RESUME set.
    + */
    +static void irq_pm_syscore_resume(void)
    +{
    + resume_irqs(true);
    +}
    +
    +static struct syscore_ops irq_pm_syscore_ops = {
    + .resume = irq_pm_syscore_resume,
    +};
    +
    +static int __init irq_pm_init_ops(void)
    +{
    + register_syscore_ops(&irq_pm_syscore_ops);
    + return 0;
    +}
    +
    +device_initcall(irq_pm_init_ops);
    +
    +/**
    + * resume_device_irqs - enable interrupt lines disabled by suspend_device_irqs()
    + *
    + * Enable all non-%IRQF_EARLY_RESUME interrupt lines previously
    + * disabled by suspend_device_irqs() that have the IRQS_SUSPENDED flag
    + * set as well as those with %IRQF_FORCE_RESUME.
    + */
    +void resume_device_irqs(void)
    +{
    + resume_irqs(false);
    +}
    EXPORT_SYMBOL_GPL(resume_device_irqs);

    /**
    --
    1.7.2.5


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