From: Dave Hansen <dave.hansen@linux.intel.com>
To: mingo@kernel.org, hpa@zytor.com, linux-kernel@vger.kernel.org,
peterz@infradead.org, tglx@linutronix.de, dzickus@redhat.com,
linux-tip-commits@vger.kernel.org
Subject: Re: [tip:perf/core] x86/nmi: Push duration printk() to irq context
Date: Mon, 10 Feb 2014 08:45:16 -0800 [thread overview]
Message-ID: <52F9021C.1030801@linux.intel.com> (raw)
In-Reply-To: <tip-rdw0au56a5ymis1u8p48c12d@git.kernel.org>
On 02/10/2014 05:29 AM, tip-bot for Peter Zijlstra wrote:
> x86/nmi: Push duration printk() to irq context
>
> Calling printk() from NMI context is bad (TM), so move it to IRQ
> context.
Bad since the I/O device that we're doing it to may be slow and make the
NMI painfully long?
I can see why it might be a bad idea, but I'm unsold that it is
*universally* a bad idea.
> In doing so we slightly change (probably wreck) the debugfs
> nmi_longest_ns thingy, in that it doesn't update to reflect the
> longest, nor does writing to it reset the count.
The reason I coded this up was that NMIs were firing off so fast that
nothing else was getting a chance to run. With this patch, at least the
printk() would come out and I'd have some idea what was going on.
next prev parent reply other threads:[~2014-02-10 16:46 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-02-10 13:29 [tip:perf/core] x86/nmi: Push duration printk() to irq context tip-bot for Peter Zijlstra
2014-02-10 16:45 ` Dave Hansen [this message]
2014-02-10 17:05 ` Peter Zijlstra
2014-02-11 15:01 ` Peter Zijlstra
2014-02-11 16:44 ` Dave Hansen
2014-02-21 21:12 ` [tip:perf/core] perf/x86: Warn to early_printk() in case irq_work is too slow tip-bot for Peter Zijlstra
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