From: Changbin Du <changbin.du@gmail.com>
To: Changbin Du <changbin.du@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
hpa@zytor.com, x86@kernel.org,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] x86/nmi: remove the irqwork from long duration nmi handler
Date: Tue, 7 Jan 2020 22:41:53 +0800 [thread overview]
Message-ID: <20200107144153.ysspbqtuwbywpjnm@mail.google.com> (raw)
In-Reply-To: <20200101072017.82990-1-changbin.du@gmail.com>
Hi, Thomas,
Have you checked this one? I think this even can consider as a fix.
On Wed, Jan 01, 2020 at 03:20:17PM +0800, Changbin Du wrote:
> First, printk is NMI context safe now since the safe printk has been
> implemented. The safe printk already has an irqwork to make NMI context
> safe.
>
> Second, the NMI irqwork actually does not work if a NMI handler causes
> panic by watchdog timeout. This NMI irqwork have no chance to run in such
> case, while the safe printk will flush its per-cpu buffer before panic.
>
> Signed-off-by: Changbin Du <changbin.du@gmail.com>
> ---
> arch/x86/include/asm/nmi.h | 1 -
> arch/x86/kernel/nmi.c | 20 +++++++++-----------
> 2 files changed, 9 insertions(+), 12 deletions(-)
>
> diff --git a/arch/x86/include/asm/nmi.h b/arch/x86/include/asm/nmi.h
> index 75ded1d13d98..9d5d949e662e 100644
> --- a/arch/x86/include/asm/nmi.h
> +++ b/arch/x86/include/asm/nmi.h
> @@ -41,7 +41,6 @@ struct nmiaction {
> struct list_head list;
> nmi_handler_t handler;
> u64 max_duration;
> - struct irq_work irq_work;
> unsigned long flags;
> const char *name;
> };
> diff --git a/arch/x86/kernel/nmi.c b/arch/x86/kernel/nmi.c
> index e676a9916c49..aa15d4f2340f 100644
> --- a/arch/x86/kernel/nmi.c
> +++ b/arch/x86/kernel/nmi.c
> @@ -104,18 +104,22 @@ static int __init nmi_warning_debugfs(void)
> }
> fs_initcall(nmi_warning_debugfs);
>
> -static void nmi_max_handler(struct irq_work *w)
> +static void nmi_check_duration(struct nmiaction *action, u64 duration)
> {
> - struct nmiaction *a = container_of(w, struct nmiaction, irq_work);
> int remainder_ns, decimal_msecs;
> - u64 whole_msecs = READ_ONCE(a->max_duration);
> + u64 whole_msecs = READ_ONCE(action->max_duration);
> +
> + if (duration < nmi_longest_ns || duration < action->max_duration)
> + return;
> +
> + action->max_duration = duration;
>
> remainder_ns = do_div(whole_msecs, (1000 * 1000));
> decimal_msecs = remainder_ns / 1000;
>
> printk_ratelimited(KERN_INFO
> "INFO: NMI handler (%ps) took too long to run: %lld.%03d msecs\n",
> - a->handler, whole_msecs, decimal_msecs);
> + action->handler, whole_msecs, decimal_msecs);
> }
>
> static int nmi_handle(unsigned int type, struct pt_regs *regs)
> @@ -142,11 +146,7 @@ static int nmi_handle(unsigned int type, struct pt_regs *regs)
> delta = sched_clock() - delta;
> trace_nmi_handler(a->handler, (int)delta, thishandled);
>
> - if (delta < nmi_longest_ns || delta < a->max_duration)
> - continue;
> -
> - a->max_duration = delta;
> - irq_work_queue(&a->irq_work);
> + nmi_check_duration(a, delta);
> }
>
> rcu_read_unlock();
> @@ -164,8 +164,6 @@ int __register_nmi_handler(unsigned int type, struct nmiaction *action)
> if (!action->handler)
> return -EINVAL;
>
> - init_irq_work(&action->irq_work, nmi_max_handler);
> -
> raw_spin_lock_irqsave(&desc->lock, flags);
>
> /*
> --
> 2.24.0
>
--
Cheers,
Changbin Du
next prev parent reply other threads:[~2020-01-07 14:42 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-01 7:20 [PATCH] x86/nmi: remove the irqwork from long duration nmi handler Changbin Du
2020-01-07 14:41 ` Changbin Du [this message]
2020-01-09 20:55 ` Thomas Gleixner
2020-01-09 21:02 ` Borislav Petkov
[not found] ` <20200110140549.xqjhrdpxllkvqbuk@mail.google.com>
[not found] ` <20200110151329.GF19453@zn.tnic>
2020-01-10 17:34 ` Changbin Du
2020-01-10 19:58 ` Borislav Petkov
2020-01-11 0:17 ` Changbin Du
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