From: Kamal Mostafa <ka...@canonical.com> Sent: Thursday, July 16, 2015 9:08 AM
> To: linux-kernel@vger.kernel.org; sta...@vger.kernel.org; kernel-
> t...@lists.ubuntu.com
> Cc: Kamal Mostafa; daniel.lezc...@linaro.org; kyungmin.p...@samsung.com;
> Damian Eppel; kg...@kernel.org; Thomas Gleixner; linux-arm-
> ker...@lists.infradead.org; m.szyprow...@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.ep...@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.kozlow...@samsung.com>
> Reviewed-by: Krzysztof Kozlowski <k.kozlow...@samsung.com>
> Tested-by: Krzysztof Kozlowski <k.kozlow...@samsung.com>
> Tested-by: Marcin Jabrzyk <m.jabr...@samsung.com>
> Signed-off-by: Damian Eppel <d.ep...@samsung.com>
> Cc: m.szyprow...@samsung.com
> Cc: kyungmin.p...@samsung.com
> Cc: daniel.lezc...@linaro.org
> Cc: kg...@kernel.org
> Cc: linux-arm-ker...@lists.infradead.org
> Link: http://lkml.kernel.org/r/1435324984-7328-1-git-send-email-
> d.ep...@samsung.com
> Signed-off-by: Thomas Gleixner <t...@linutronix.de>
> Signed-off-by: Kamal Mostafa <ka...@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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