[PATCH 3.19.y-ckt 173/251] clocksource: exynos_mct: Avoid blocking calls in the cpu hotplug notifier
Duan Andy
fugang.duan at freescale.com
Thu Jul 16 01:14:57 PDT 2015
From: Krzysztof Kozlowski <k.kozlowski at samsung.com> Sent: Thursday, July 16, 2015 2:56 PM
> To: Duan Fugang-B38611
> Cc: Kamal Mostafa; linux-kernel at vger.kernel.org; stable at vger.kernel.org;
> kernel-team at lists.ubuntu.com; daniel.lezcano at linaro.org; Damian Eppel;
> kyungmin.park at samsung.com; kgene at kernel.org; Thomas Gleixner; linux-arm-
> kernel at lists.infradead.org; m.szyprowski at samsung.com
> 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 <fugang.duan at freescale.com>:
> > From: Kamal Mostafa <kamal at canonical.com> Sent: Thursday, July 16,
> > 2015 9:08 AM
> >> To: linux-kernel at vger.kernel.org; stable at vger.kernel.org; kernel-
> >> team at lists.ubuntu.com
> >> Cc: Kamal Mostafa; daniel.lezcano at linaro.org;
> >> kyungmin.park at samsung.com; Damian Eppel; kgene at kernel.org; Thomas
> >> Gleixner; linux-arm- kernel at lists.infradead.org;
> >> m.szyprowski at 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 at 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 at samsung.com>
> >> Reviewed-by: Krzysztof Kozlowski <k.kozlowski at samsung.com>
> >> Tested-by: Krzysztof Kozlowski <k.kozlowski at samsung.com>
> >> Tested-by: Marcin Jabrzyk <m.jabrzyk at samsung.com>
> >> Signed-off-by: Damian Eppel <d.eppel at samsung.com>
> >> Cc: m.szyprowski at samsung.com
> >> Cc: kyungmin.park at samsung.com
> >> Cc: daniel.lezcano at linaro.org
> >> Cc: kgene at kernel.org
> >> Cc: linux-arm-kernel at lists.infradead.org
> >> Link: http://lkml.kernel.org/r/1435324984-7328-1-git-send-email-
> >> d.eppel at samsung.com
> >> Signed-off-by: Thomas Gleixner <tglx at linutronix.de>
> >> Signed-off-by: Kamal Mostafa <kamal at 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) ?
>
> 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
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