linux-kernel - Re: [PATCH 2/2] timer: really raise softirq if there is irq

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Message-ID: <52EBF8FE.3080608@linutronix.de>
Date:	Fri, 31 Jan 2014 20:26:54 +0100
From:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:	Steven Rostedt <rostedt@...dmis.org>, peterz@...radead.org,
	paulmck@...ux.vnet.ibm.com
CC:	linux-rt-users@...r.kernel.org, linux-kernel@...r.kernel.org,
	tglx@...utronix.de, Clark Williams <williams@...hat.com>
Subject: Re: [PATCH 2/2] timer: really raise softirq if there is irq_work
 to do

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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