From: Michael Ellerman <patch-notifications@ellerman•id.au>
To: Nicholas Piggin <npiggin@gmail•com>, linuxppc-dev@lists•ozlabs.org
Cc: Nicholas Piggin <npiggin@gmail•com>
Subject: Re: [01/11] powerpc/64: irq_work avoid interrupt when called with hardware irqs enabled
Date: Tue, 5 Jun 2018 00:10:44 +1000 (AEST) [thread overview]
Message-ID: <40zxfs0Y5Zz9s5b@ozlabs.org> (raw)
In-Reply-To: <20180504171935.25410-2-npiggin@gmail.com>
On Fri, 2018-05-04 at 17:19:25 UTC, Nicholas Piggin wrote:
> irq_work_raise should not cause a decrementer exception unless it is
> called from NMI context. Doing so often just results in an immediate
> masked decrementer interrupt:
>
> <...>-550 90d... 4us : update_curr_rt <-dequeue_task_rt
> <...>-550 90d... 5us : dbs_update_util_handler <-update_curr_rt
> <...>-550 90d... 6us : arch_irq_work_raise <-irq_work_queue
> <...>-550 90d... 7us : soft_nmi_interrupt <-soft_nmi_common
> <...>-550 90d... 7us : printk_nmi_enter <-soft_nmi_interrupt
> <...>-550 90d.Z. 8us : rcu_nmi_enter <-soft_nmi_interrupt
> <...>-550 90d.Z. 9us : rcu_nmi_exit <-soft_nmi_interrupt
> <...>-550 90d... 9us : printk_nmi_exit <-soft_nmi_interrupt
> <...>-550 90d... 10us : cpuacct_charge <-update_curr_rt
>
> The soft_nmi_interrupt here is the call into the watchdog, due to the
> decrementer interrupt firing with irqs soft-disabled. This is
> harmless, but sub-optimal.
>
> When it's not called from NMI context or with interrupts enabled, mark
> the decrementer pending in the irq_happened mask directly, rather than
> having the masked decrementer interupt handler do it. This will be
> replayed at the next local_irq_enable. See the comment for details.
>
> Signed-off-by: Nicholas Piggin <npiggin@gmail•com>
Series applied to powerpc next, thanks.
https://git.kernel.org/powerpc/c/ebb37cf3ffd39fdb6ec5b07111f8bb
cheers
next prev parent reply other threads:[~2018-06-04 14:10 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-04 17:19 [PATCH 00/11] assortment of timer, watchdog, interrupt Nicholas Piggin
2018-05-04 17:19 ` [PATCH 01/11] powerpc/64: irq_work avoid interrupt when called with hardware irqs enabled Nicholas Piggin
2018-06-04 14:10 ` Michael Ellerman [this message]
2018-05-04 17:19 ` [PATCH 02/11] powerpc/pseries: put cede MSR[EE] check under IRQ_SOFT_MASK_DEBUG Nicholas Piggin
2018-05-04 17:19 ` [PATCH 03/11] powerpc/64s: make PACA_IRQ_HARD_DIS track MSR[EE] closely Nicholas Piggin
2018-05-04 17:19 ` [PATCH 04/11] powerpc/64s: micro-optimise __hard_irq_enable() for mtmsrd L=1 support Nicholas Piggin
2018-05-04 17:19 ` [PATCH 05/11] powerpc/64: remove start_tb and accum_tb from thread_struct Nicholas Piggin
2018-05-04 17:19 ` [PATCH 06/11] powerpc/pseries: lparcfg calculate PURR on demand Nicholas Piggin
2018-05-04 17:19 ` [PATCH 07/11] powerpc: generic clockevents broadcast receiver call tick_receive_broadcast Nicholas Piggin
2018-05-05 14:38 ` kbuild test robot
2018-05-04 17:19 ` [PATCH 08/11] powerpc: allow soft-NMI watchdog to cover timer interrupts with large decrementers Nicholas Piggin
2018-05-04 17:19 ` [PATCH 09/11] powerpc: move timer broadcast code under GENERIC_CLOCKEVENTS_BROADCAST ifdef Nicholas Piggin
2018-05-04 17:19 ` [PATCH 10/11] powerpc: move a stray NMI IPI case under NMI_IPI ifdef Nicholas Piggin
2018-05-04 17:19 ` [PATCH 11/11] powerpc/time: account broadcast timer event interrupts separately Nicholas Piggin
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