From: Duan Andy <fugang.duan@freescale.com>
To: Kamal Mostafa <kamal@canonical.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "stable@vger.kernel.org" <stable@vger.kernel.org>,
        "kernel-team@lists.ubuntu.com" <kernel-team@lists.ubuntu.com>
CC: "daniel.lezcano@linaro.org" <daniel.lezcano@linaro.org>,
        "kyungmin.park@samsung.com" <kyungmin.park@samsung.com>,
        Damian Eppel <d.eppel@samsung.com>,
        "kgene@kernel.org" <kgene@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        "linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>,
        "m.szyprowski@samsung.com" <m.szyprowski@samsung.com>
Subject: RE: [PATCH 3.19.y-ckt 173/251] clocksource: exynos_mct: Avoid
 blocking calls in the cpu hotplug notifier
Thread-Topic: [PATCH 3.19.y-ckt 173/251] clocksource: exynos_mct: Avoid
 blocking calls in the cpu hotplug notifier
Thread-Index: AQHQv2ULRJkCJ+tWi0is9V1wrJLW1p3dpClQ
Date: Thu, 16 Jul 2015 06:37:32 +0000
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References: <1437008972-9140-1-git-send-email-kamal@canonical.com>
 <1437008972-9140-174-git-send-email-kamal@canonical.com>
In-Reply-To: <1437008972-9140-174-git-send-email-kamal@canonical.com>
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From: Kamal Mostafa <kamal@canonical.com> Sent: Thursday, July 16, 2015 9:08 AM
> To: linux-kernel@vger.kernel.org; stable@vger.kernel.org; kernel-
> team@lists.ubuntu.com
> Cc: Kamal Mostafa; daniel.lezcano@linaro.org; kyungmin.park@samsung.com;
> Damian Eppel; kgene@kernel.org; Thomas Gleixner; linux-arm-
> kernel@lists.infradead.org; m.szyprowski@samsung.com
> Subject: [PATCH 3.19.y-ckt 173/251] clocksource: exynos_mct: Avoid
> blocking calls in the cpu hotplug notifier
> 
> 3.19.8-ckt4 -stable review patch.  If anyone has any objections, please
> let me know.
> 
> ------------------
> 
> From: Damian Eppel <d.eppel@samsung.com>
> 
> commit 56a94f13919c0db5958611b388e1581b4852f3c9 upstream.
> 
> Whilst testing cpu hotplug events on kernel configured with DEBUG_PREEMPT
> and DEBUG_ATOMIC_SLEEP we get following BUG message, caused by calling
> request_irq() and free_irq() in the context of hotplug notification
> (which is in this case atomic context).
> 
> [   40.785859] CPU1: Software reset
> [   40.786660] BUG: sleeping function called from invalid context at
> mm/slub.c:1241
> [   40.786668] in_atomic(): 1, irqs_disabled(): 128, pid: 0, name:
> swapper/1
> [   40.786678] Preemption disabled at:[<  (null)>]   (null)
> [   40.786681]
> [   40.786692] CPU: 1 PID: 0 Comm: swapper/1 Not tainted 3.19.0-rc4-
> 00024-g7dca860 #36
> [   40.786698] Hardware name: SAMSUNG EXYNOS (Flattened Device Tree)
> [   40.786728] [<c0014a00>] (unwind_backtrace) from [<c0011980>]
> (show_stack+0x10/0x14)
> [   40.786747] [<c0011980>] (show_stack) from [<c0449ba0>]
> (dump_stack+0x70/0xbc)
> [   40.786767] [<c0449ba0>] (dump_stack) from [<c00c6124>]
> (kmem_cache_alloc+0xd8/0x170)
> [   40.786785] [<c00c6124>] (kmem_cache_alloc) from [<c005d6f8>]
> (request_threaded_irq+0x64/0x128)
> [   40.786804] [<c005d6f8>] (request_threaded_irq) from [<c0350b8c>]
> (exynos4_local_timer_setup+0xc0/0x13c)
> [   40.786820] [<c0350b8c>] (exynos4_local_timer_setup) from [<c0350ca8>]
> (exynos4_mct_cpu_notify+0x30/0xa8)
> [   40.786838] [<c0350ca8>] (exynos4_mct_cpu_notify) from [<c003b330>]
> (notifier_call_chain+0x44/0x84)
> [   40.786857] [<c003b330>] (notifier_call_chain) from [<c0022fd4>]
> (__cpu_notify+0x28/0x44)
> [   40.786873] [<c0022fd4>] (__cpu_notify) from [<c0013714>]
> (secondary_start_kernel+0xec/0x150)
> [   40.786886] [<c0013714>] (secondary_start_kernel) from [<40008764>]
> (0x40008764)
> 
> Interrupts cannot be requested/freed in the CPU_STARTING/CPU_DYING
> notifications which run on the hotplugged cpu with interrupts and
> preemption disabled.
> 
> To avoid the issue, request the interrupts for all possible cpus in the
> boot code. The interrupts are marked NO_AUTOENABLE to avoid a racy
> request_irq/disable_irq() sequence. The flag prevents the
> request_irq() code from enabling the interrupt immediately.
> 
> The interrupt is then enabled in the CPU_STARTING notifier of the
> hotplugged cpu and again disabled with disable_irq_nosync() in the
> CPU_DYING notifier.
> 
> [ tglx: Massaged changelog to match the patch ]
> 
> Fixes: 7114cd749a12 ("clocksource: exynos_mct: use (request/free)_irq
> calls for local timer registration")
> Reported-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
> Reviewed-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
> Tested-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
> Tested-by: Marcin Jabrzyk <m.jabrzyk@samsung.com>
> Signed-off-by: Damian Eppel <d.eppel@samsung.com>
> Cc: m.szyprowski@samsung.com
> Cc: kyungmin.park@samsung.com
> Cc: daniel.lezcano@linaro.org
> Cc: kgene@kernel.org
> Cc: linux-arm-kernel@lists.infradead.org
> Link: http://lkml.kernel.org/r/1435324984-7328-1-git-send-email-
> d.eppel@samsung.com
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> Signed-off-by: Kamal Mostafa <kamal@canonical.com>
> ---
>  drivers/clocksource/exynos_mct.c | 43 ++++++++++++++++++++++++++++------
> ------
>  1 file changed, 30 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/clocksource/exynos_mct.c
> b/drivers/clocksource/exynos_mct.c
> index 83564c9..c844616 100644
> --- a/drivers/clocksource/exynos_mct.c
> +++ b/drivers/clocksource/exynos_mct.c
> @@ -466,15 +466,12 @@ static int exynos4_local_timer_setup(struct
> clock_event_device *evt)
>  	exynos4_mct_write(TICK_BASE_CNT, mevt->base + MCT_L_TCNTB_OFFSET);
> 
>  	if (mct_int_type == MCT_INT_SPI) {
> -		evt->irq = mct_irqs[MCT_L0_IRQ + cpu];
> -		if (request_irq(evt->irq, exynos4_mct_tick_isr,
> -				IRQF_TIMER | IRQF_NOBALANCING,
> -				evt->name, mevt)) {
> -			pr_err("exynos-mct: cannot register IRQ %d\n",
> -				evt->irq);
> +
> +		if (evt->irq == -1)
>  			return -EIO;
> -		}
> -		irq_force_affinity(mct_irqs[MCT_L0_IRQ + cpu],
> cpumask_of(cpu));
> +
> +		irq_force_affinity(evt->irq, cpumask_of(cpu));
> +		enable_irq(evt->irq);
>  	} else {
>  		enable_percpu_irq(mct_irqs[MCT_L0_IRQ], 0);

In here, why not use enable_percpu_irq(evt->irq) ?

>  	}
> @@ -487,10 +484,12 @@ static int exynos4_local_timer_setup(struct
> clock_event_device *evt)  static void exynos4_local_timer_stop(struct
> clock_event_device *evt)  {
>  	evt->set_mode(CLOCK_EVT_MODE_UNUSED, evt);
> -	if (mct_int_type == MCT_INT_SPI)
> -		free_irq(evt->irq, this_cpu_ptr(&percpu_mct_tick));
> -	else
> +	if (mct_int_type == MCT_INT_SPI) {
> +		if (evt->irq != -1)
> +			disable_irq_nosync(evt->irq);
> +	} else {
>  		disable_percpu_irq(mct_irqs[MCT_L0_IRQ]);

In here, why not use disable_percpu_irq(evt->irq) ?


> +	}
>  }
> 
>  static int exynos4_mct_cpu_notify(struct notifier_block *self, @@ -522,7
> +521,7 @@ static struct notifier_block exynos4_mct_cpu_nb = {
> 
>  static void __init exynos4_timer_resources(struct device_node *np, void
> __iomem *base)  {
> -	int err;
> +	int err, cpu;
>  	struct mct_clock_event_device *mevt =
> this_cpu_ptr(&percpu_mct_tick);
>  	struct clk *mct_clk, *tick_clk;
> 
> @@ -549,7 +548,25 @@ static void __init exynos4_timer_resources(struct
> device_node *np, void __iomem
>  		WARN(err, "MCT: can't request IRQ %d (%d)\n",
>  		     mct_irqs[MCT_L0_IRQ], err);
>  	} else {
> -		irq_set_affinity(mct_irqs[MCT_L0_IRQ], cpumask_of(0));
> +		for_each_possible_cpu(cpu) {
> +			int mct_irq = mct_irqs[MCT_L0_IRQ + cpu];
> +			struct mct_clock_event_device *pcpu_mevt =
> +				per_cpu_ptr(&percpu_mct_tick, cpu);
> +
> +			pcpu_mevt->evt.irq = -1;
> +
> +			irq_set_status_flags(mct_irq, IRQ_NOAUTOEN);
> +			if (request_irq(mct_irq,
> +					exynos4_mct_tick_isr,
> +					IRQF_TIMER | IRQF_NOBALANCING,
> +					pcpu_mevt->name, pcpu_mevt)) {
> +				pr_err("exynos-mct: cannot register IRQ
> (cpu%d)\n",
> +									cpu);
> +
> +				continue;
> +			}
> +			pcpu_mevt->evt.irq = mct_irq;
> +		}
>  	}
> 
>  	err = register_cpu_notifier(&exynos4_mct_cpu_nb);
> --
> 1.9.1
--
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