| Message ID | 1435324984-7328-1-git-send-email-d.eppel@samsung.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 06/26/2015 03:23 PM, Damian Eppel wrote: > This is to fix an issue of sleeping in atomic context when processing > hotplug notifications in Exynos MCT(Multi-Core Timer). > The issue was reproducible on Exynos 3250 (Rinato board) and Exynos 5420 > (Arndale Octa board). > > 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). Applied as a 4.2 fix. Should it be tagged stable@ ?
On Mon, 29 Jun 2015, Daniel Lezcano wrote: > On 06/26/2015 03:23 PM, Damian Eppel wrote: > > This is to fix an issue of sleeping in atomic context when processing > > hotplug notifications in Exynos MCT(Multi-Core Timer). > > The issue was reproducible on Exynos 3250 (Rinato board) and Exynos 5420 > > (Arndale Octa board). > > > > 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). > > Applied as a 4.2 fix. > > Should it be tagged stable@ ? I have that one queued in tip/timers/urgent already. Please check my branches before picking up stuff. Thanks, tglx -- To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 06/29/2015 11:24 AM, Thomas Gleixner wrote: > On Mon, 29 Jun 2015, Daniel Lezcano wrote: > >> On 06/26/2015 03:23 PM, Damian Eppel wrote: >>> This is to fix an issue of sleeping in atomic context when processing >>> hotplug notifications in Exynos MCT(Multi-Core Timer). >>> The issue was reproducible on Exynos 3250 (Rinato board) and Exynos 5420 >>> (Arndale Octa board). >>> >>> 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). >> >> Applied as a 4.2 fix. >> >> Should it be tagged stable@ ? > > I have that one queued in tip/timers/urgent already. Please check my > branches before picking up stuff. Mmmh, yep. I thought I refreshed my branch. Now I see it. Thanks for the heads up. -- Daniel
2015-06-29 18:19 GMT+09:00 Daniel Lezcano <daniel.lezcano@linaro.org>: > On 06/26/2015 03:23 PM, Damian Eppel wrote: >> >> This is to fix an issue of sleeping in atomic context when processing >> hotplug notifications in Exynos MCT(Multi-Core Timer). >> The issue was reproducible on Exynos 3250 (Rinato board) and Exynos 5420 >> (Arndale Octa board). >> >> 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). > > > Applied as a 4.2 fix. > > Should it be tagged stable@ ? The patch and commit in tip have cc-stable and fixes tags, so everything is fine. Thanks! Krzysztof -- To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/clocksource/exynos_mct.c b/drivers/clocksource/exynos_mct.c index 935b059..9064ff7 100644 --- a/drivers/clocksource/exynos_mct.c +++ b/drivers/clocksource/exynos_mct.c @@ -462,15 +462,12 @@ 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); } @@ -483,10 +480,12 @@ 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, @@ -518,7 +517,7 @@ 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; @@ -545,7 +544,25 @@ 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);
This is to fix an issue of sleeping in atomic context when processing hotplug notifications in Exynos MCT(Multi-Core Timer). The issue was reproducible on Exynos 3250 (Rinato board) and Exynos 5420 (Arndale Octa board). 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). root@target:~# echo 0 > /sys/devices/system/cpu/cpu1/online [ 25.157867] IRQ18 no longer affine to CPU1 ... [ 25.158445] CPU1: shutdown root@target:~# echo 1 > /sys/devices/system/cpu/cpu1/online [ 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) Solution: Clockevent irqs cannot be requested/freed every time cpu is hot-plugged/unplugged as CPU_STARTING/CPU_DYING notifications that signals hotplug or unplug events are sent with both preemption and local interrupts disabled. Since request_irq() may sleep it is moved to the initialization stage and performed for all possible cpus prior putting them online. Then, in the case of hotplug event the irq asociated with the given cpu will simply be enabled. Similarly on cpu unplug event the interrupt is not freed but just disabled. Note that after successful request_irq() call for a clockevent device associated to given cpu the requested irq is disabled (via disable_irq()). That is to make things symmetric as we expect hotplug event as a next thing (which will enable irq again). This should not pose any problems because at the time of requesting irq the clockevent device is not fully initialized yet, therefore should not produce interrupts at that point. For disabling an irq at cpu unplug notification disable_irq_nosync() is chosen which is a non-blocking function. This again shouldn't be a problem as prior sending CPU_DYING notification interrupts are migrated away from the cpu. Fixes: 7114cd749a12 ("clocksource: exynos_mct: use (request/free)_irq calls for local timer registration") Signed-off-by: Damian Eppel <d.eppel@samsung.com> Cc: <stable@vger.kernel.org> 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 on Arndale Octa Board) Tested-by: Marcin Jabrzyk <m.jabrzyk@samsung.com> (Tested on Rinato B2 (Exynos 3250) board) --- Notes: Changes since v1: o added Krzysztof's and Marcin's Reviewed-by / Tested-by with information about the test HW. Changes since v2: o requesting mct_irq already in disabled state instead of calling disable_irq() right after request_irq(). drivers/clocksource/exynos_mct.c | 43 ++++++++++++++++++++++++++++------------ 1 file changed, 30 insertions(+), 13 deletions(-)