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Date: Tue, 15 Feb 2011 18:29:41 +0100
From: Richard Cochran <richardcochran@gmail.com>
To: John Stultz <john.stultz@linaro.org>
Cc: linux-kernel@vger.kernel.org, linux-api@vger.kernel.org,
        netdev@vger.kernel.org, Alan Cox <alan@lxorguk.ukuu.org.uk>,
        Arnd Bergmann <arnd@arndb.de>, Christoph Lameter <cl@linux.com>,
        David Miller <davem@davemloft.net>, Krzysztof Halasa <khc@pm.waw.pl>,
        Peter Zijlstra <peterz@infradead.org>,
        Rodolfo Giometti <giometti@linux.it>,
        Thomas Gleixner <tglx@linutronix.de>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        "H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
        Mike Frysinger <vapier@gentoo.org>, Paul Mackerras <paulus@samba.org>,
        Russell King <linux@arm.linux.org.uk>
Subject: Re: [PATCH V10 12/15] ptp: Added a brand new class driver for ptp
 clocks.
Message-ID: <20110215172941.GA21150@riccoc20.at.omicron.at>
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On Fri, Feb 11, 2011 at 09:15:24AM +0100, Richard Cochran wrote:
> On Tue, Feb 01, 2011 at 06:00:31PM -0800, John Stultz wrote:
> > So what is serializing access to the timestamp_event_queue here? I don't
> > see any usage of tsevq_mux by the callers. Am I missing it? It looks
> > like its called from interrupt context, so do you really need a spinlock
> > and not a mutex here?
> 
> The external timestamp FIFO is written only from interrupt context.

Oops, I lied. After reworking the phyter driver, I find that I want to
enqueue time stamps from non-interrupt contexts, too.

So, you are right. This will need a spin lock...

Thanks,

Richard