Message-ID: <52EBF8FE.3080608@linutronix.de>
Date: Fri, 31 Jan 2014 20:26:54 +0100
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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To: Steven Rostedt <rostedt@goodmis.org>, peterz@infradead.org,
        paulmck@linux.vnet.ibm.com
CC: linux-rt-users@vger.kernel.org, linux-kernel@vger.kernel.org,
        tglx@linutronix.de, Clark Williams <williams@redhat.com>
Subject: Re: [PATCH 2/2] timer: really raise softirq if there is irq_work
 to do
References: <1391178845-15837-1-git-send-email-bigeasy@linutronix.de>	<1391178845-15837-2-git-send-email-bigeasy@linutronix.de>	<20140131120757.594e24d6@gandalf.local.home>	<20140131174227.GN9012@linux.vnet.ibm.com> <20140131125719.73340f6e@gandalf.local.home>
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Sender: linux-kernel-owner@vger.kernel.org

On 01/31/2014 06:57 PM, Steven Rostedt wrote:

> In vanilla Linux, irq_work_run() is called from update_process_times()
> when it is called from the timer interrupt. In -rt, there's reasons we

and in vanilla Linux some architectures (like x86 or sparc to name just
a few) overwrite arch_irq_work_raise() which means they provide
their "own" interrupt like callback. That means on those architectures
irq_work_run() gets invoked twice: once via update_process_times() and
via and once the custom interface.
So my question to the original inventor of this code: Peter, do we
really need that arch specific callback? Wouldn't one be enough? Is it
that critical that it can't wait to the next timer tick?

Sebastian

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