[3.19.y-ckt,173/251] clocksource: exynos_mct: Avoid blocking calls in the cpu hotplug notifier

Commit Message

Kamal Mostafa July 16, 2015, 1:08 a.m. UTC

3.19.8-ckt4 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Damian Eppel <[e-mail]>

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 <[e-mail]>
Reviewed-by: Krzysztof Kozlowski <[e-mail]>
Tested-by: Krzysztof Kozlowski <[e-mail]>
Tested-by: Marcin Jabrzyk <[e-mail]>
Signed-off-by: Damian Eppel <[e-mail]>
Cc: [e-mail]
Cc: [e-mail]
Cc: [e-mail]
Cc: [e-mail]
Cc: [e-mail]
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Thomas Gleixner <[e-mail]>
Signed-off-by: Kamal Mostafa <[e-mail]>
---
 drivers/clocksource/exynos_mct.c | 43 ++++++++++++++++++++++++++++------------
 1 file changed, 30 insertions(+), 13 deletions(-)

Comments

[e-mail] July 16, 2015, 6:37 a.m. UTC | #1

From: Kamal Mostafa <[e-mail]> Sent: Thursday, July 16, 2015 9:08 AM
> To: [e-mail]; [e-mail]; kernel-
> [e-mail]
> Cc: Kamal Mostafa; [e-mail]; [e-mail];
> Damian Eppel; [e-mail]; Thomas Gleixner; linux-arm-
> [e-mail]; [e-mail]
> 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 <[e-mail]>
> 
> 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 <[e-mail]>
> Reviewed-by: Krzysztof Kozlowski <[e-mail]>
> Tested-by: Krzysztof Kozlowski <[e-mail]>
> Tested-by: Marcin Jabrzyk <[e-mail]>
> Signed-off-by: Damian Eppel <[e-mail]>
> Cc: [e-mail]
> Cc: [e-mail]
> Cc: [e-mail]
> Cc: [e-mail]
> Cc: [e-mail]
> Link: http://lkml.kernel.org/r/1435324984-7328-1-git-send-email-
> [e-mail]
> Signed-off-by: Thomas Gleixner <[e-mail]>
> Signed-off-by: Kamal Mostafa <[e-mail]>
> ---
>  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

Krzysztof Kozlowski July 16, 2015, 6:55 a.m. UTC | #2

2015-07-16 15:37 GMT+09:00 Duan Andy <[e-mail]>:
> From: Kamal Mostafa <[e-mail]> Sent: Thursday, July 16, 2015 9:08 AM
>> To: [e-mail]; [e-mail]; kernel-
>> [e-mail]
>> Cc: Kamal Mostafa; [e-mail]; [e-mail];
>> Damian Eppel; [e-mail]; Thomas Gleixner; linux-arm-
>> [e-mail]; [e-mail]
>> 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 <[e-mail]>
>>
>> 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 <[e-mail]>
>> Reviewed-by: Krzysztof Kozlowski <[e-mail]>
>> Tested-by: Krzysztof Kozlowski <[e-mail]>
>> Tested-by: Marcin Jabrzyk <[e-mail]>
>> Signed-off-by: Damian Eppel <[e-mail]>
>> Cc: [e-mail]
>> Cc: [e-mail]
>> Cc: [e-mail]
>> Cc: [e-mail]
>> Cc: [e-mail]
>> Link: http://lkml.kernel.org/r/1435324984-7328-1-git-send-email-
>> [e-mail]
>> Signed-off-by: Thomas Gleixner <[e-mail]>
>> Signed-off-by: Kamal Mostafa <[e-mail]>
>> ---
>>  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) ?

You know this is just a semi-automatic stable backport and this was
already merged to mainline?

Best regards,
Krzysztof

[e-mail] July 16, 2015, 8:14 a.m. UTC | #3

From: Krzysztof Kozlowski <[e-mail]> Sent: Thursday, July 16, 2015 2:56 PM
> To: Duan Fugang-B38611
> Cc: Kamal Mostafa; [e-mail]; [e-mail];
> [e-mail]; [e-mail]; Damian Eppel;
> [e-mail]; [e-mail]; Thomas Gleixner; linux-arm-
> [e-mail]; [e-mail]
> Subject: Re: [PATCH 3.19.y-ckt 173/251] clocksource: exynos_mct: Avoid
> blocking calls in the cpu hotplug notifier
> 
> 2015-07-16 15:37 GMT+09:00 Duan Andy <[e-mail]>:
> > From: Kamal Mostafa <[e-mail]> Sent: Thursday, July 16,
> > 2015 9:08 AM
> >> To: [e-mail]; [e-mail]; kernel-
> >> [e-mail]
> >> Cc: Kamal Mostafa; [e-mail];
> >> [e-mail]; Damian Eppel; [e-mail]; Thomas
> >> Gleixner; linux-arm- [e-mail];
> >> [e-mail]
> >> 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 <[e-mail]>
> >>
> >> 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 <[e-mail]>
> >> Reviewed-by: Krzysztof Kozlowski <[e-mail]>
> >> Tested-by: Krzysztof Kozlowski <[e-mail]>
> >> Tested-by: Marcin Jabrzyk <[e-mail]>
> >> Signed-off-by: Damian Eppel <[e-mail]>
> >> Cc: [e-mail]
> >> Cc: [e-mail]
> >> Cc: [e-mail]
> >> Cc: [e-mail]
> >> Cc: [e-mail]
> >> Link: http://lkml.kernel.org/r/1435324984-7328-1-git-send-email-
> >> [e-mail]
> >> Signed-off-by: Thomas Gleixner <[e-mail]>
> >> Signed-off-by: Kamal Mostafa <[e-mail]>
> >> ---
> >>  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) ?
> 
> You know this is just a semi-automatic stable backport and this was
> already merged to mainline?
> 
> Best regards,
> Krzysztof

Yes, I know. Do you know the reason why not enable other cpus irq ?
I want to confirm whether it is right after below change ?
enable_percpu_irq(mct_irqs[MCT_L0_IRQ], 0); -> enable_percpu_irq(evt->irq, 0);
disable_percpu_irq(mct_irqs[MCT_L0_IRQ]) -> disable_percpu_irq(evt->irq)

Regards,
Andy

Krzysztof Kozlowski July 16, 2015, 9:52 a.m. UTC | #4

2015-07-16 17:14 GMT+09:00 Duan Andy <[e-mail]>:
> From: Krzysztof Kozlowski <[e-mail]> Sent: Thursday, July 16, 2015 2:56 PM
>> To: Duan Fugang-B38611
>> Cc: Kamal Mostafa; [e-mail]; [e-mail];
>> [e-mail]; [e-mail]; Damian Eppel;
>> [e-mail]; [e-mail]; Thomas Gleixner; linux-arm-
>> [e-mail]; [e-mail]
>> Subject: Re: [PATCH 3.19.y-ckt 173/251] clocksource: exynos_mct: Avoid
>> blocking calls in the cpu hotplug notifier
>>
>> 2015-07-16 15:37 GMT+09:00 Duan Andy <[e-mail]>:
>> > From: Kamal Mostafa <[e-mail]> Sent: Thursday, July 16,
>> > 2015 9:08 AM
>> >> To: [e-mail]; [e-mail]; kernel-
>> >> [e-mail]
>> >> Cc: Kamal Mostafa; [e-mail];
>> >> [e-mail]; Damian Eppel; [e-mail]; Thomas
>> >> Gleixner; linux-arm- [e-mail];
>> >> [e-mail]
>> >> 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 <[e-mail]>
>> >>
>> >> 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 <[e-mail]>
>> >> Reviewed-by: Krzysztof Kozlowski <[e-mail]>
>> >> Tested-by: Krzysztof Kozlowski <[e-mail]>
>> >> Tested-by: Marcin Jabrzyk <[e-mail]>
>> >> Signed-off-by: Damian Eppel <[e-mail]>
>> >> Cc: [e-mail]
>> >> Cc: [e-mail]
>> >> Cc: [e-mail]
>> >> Cc: [e-mail]
>> >> Cc: [e-mail]
>> >> Link: http://lkml.kernel.org/r/1435324984-7328-1-git-send-email-
>> >> [e-mail]
>> >> Signed-off-by: Thomas Gleixner <[e-mail]>
>> >> Signed-off-by: Kamal Mostafa <[e-mail]>
>> >> ---
>> >>  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) ?
>>
>> You know this is just a semi-automatic stable backport and this was
>> already merged to mainline?
>>
>> Best regards,
>> Krzysztof
>
> Yes, I know. Do you know the reason why not enable other cpus irq ?
> I want to confirm whether it is right after below change ?
> enable_percpu_irq(mct_irqs[MCT_L0_IRQ], 0); -> enable_percpu_irq(evt->irq, 0);
> disable_percpu_irq(mct_irqs[MCT_L0_IRQ]) -> disable_percpu_irq(evt->irq)

This is a backport so are there any objections about this patch? Do
you think the patch is invalid so it should not be backported to
stable?

Best regards,
Krzysztof

[e-mail] July 17, 2015, 1:29 a.m. UTC | #5

From: Krzysztof Kozlowski <[e-mail]> Sent: Thursday, July 16, 2015 5:52 PM
> To: Duan Fugang-B38611
> Cc: Krzysztof Kozlowski; Kamal Mostafa; [e-mail]; linux-
> [e-mail]; [e-mail]; Damian Eppel;
> [e-mail]; [e-mail]; Thomas Gleixner;
> [e-mail]; [e-mail]; kernel-
> [e-mail]
> Subject: Re: [PATCH 3.19.y-ckt 173/251] clocksource: exynos_mct: Avoid
> blocking calls in the cpu hotplug notifier
> 
> 2015-07-16 17:14 GMT+09:00 Duan Andy <[e-mail]>:
> > From: Krzysztof Kozlowski <[e-mail]> Sent: Thursday,
> > July 16, 2015 2:56 PM
> >> To: Duan Fugang-B38611
> >> Cc: Kamal Mostafa; [e-mail];
> >> [e-mail]; [e-mail];
> >> [e-mail]; Damian Eppel; [e-mail];
> >> [e-mail]; Thomas Gleixner; linux-arm-
> >> [e-mail]; [e-mail]
> >> Subject: Re: [PATCH 3.19.y-ckt 173/251] clocksource: exynos_mct:
> >> Avoid blocking calls in the cpu hotplug notifier
> >>
> >> 2015-07-16 15:37 GMT+09:00 Duan Andy <[e-mail]>:
> >> > From: Kamal Mostafa <[e-mail]> Sent: Thursday, July 16,
> >> > 2015 9:08 AM
> >> >> To: [e-mail]; [e-mail]; kernel-
> >> >> [e-mail]
> >> >> Cc: Kamal Mostafa; [e-mail];
> >> >> [e-mail]; Damian Eppel; [e-mail]; Thomas
> >> >> Gleixner; linux-arm- [e-mail];
> >> >> [e-mail]
> >> >> 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 <[e-mail]>
> >> >>
> >> >> 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 <[e-mail]>
> >> >> Reviewed-by: Krzysztof Kozlowski <[e-mail]>
> >> >> Tested-by: Krzysztof Kozlowski <[e-mail]>
> >> >> Tested-by: Marcin Jabrzyk <[e-mail]>
> >> >> Signed-off-by: Damian Eppel <[e-mail]>
> >> >> Cc: [e-mail]
> >> >> Cc: [e-mail]
> >> >> Cc: [e-mail]
> >> >> Cc: [e-mail]
> >> >> Cc: [e-mail]
> >> >> Link: http://lkml.kernel.org/r/1435324984-7328-1-git-send-email-
> >> >> [e-mail]
> >> >> Signed-off-by: Thomas Gleixner <[e-mail]>
> >> >> Signed-off-by: Kamal Mostafa <[e-mail]>
> >> >> ---
> >> >>  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) ?
> >>
> >> You know this is just a semi-automatic stable backport and this was
> >> already merged to mainline?
> >>
> >> Best regards,
> >> Krzysztof
> >
> > Yes, I know. Do you know the reason why not enable other cpus irq ?
> > I want to confirm whether it is right after below change ?
> > enable_percpu_irq(mct_irqs[MCT_L0_IRQ], 0); ->
> > enable_percpu_irq(evt->irq, 0);
> > disable_percpu_irq(mct_irqs[MCT_L0_IRQ]) ->
> > disable_percpu_irq(evt->irq)
> 
> This is a backport so are there any objections about this patch? Do you
> think the patch is invalid so it should not be backported to stable?
> 
No, I just have some questions about the original code design.
Your patch has no problem.

Regards,
Andy

Patch

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);
 	}
@@ -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]);
+	}
 }
 
 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);