linux-kernel - Re: [PATCH] fix a Sparse warning in the arch/x86/kernel/irq

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Date:	Tue, 13 Aug 2013 07:33:57 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	anish singh <anish198519851985@...il.com>
Cc:	Shailaja Neelam <neelamshaila@...il.com>,
	Frédéric Weisbecker <fweisbec@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	james.hogan@...tec.com,
	linux-kernel-mail <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH] fix a Sparse warning in the arch/x86/kernel/irq_work.c
 file

On Tue, 13 Aug 2013 11:09:34 +0530
anish singh <anish198519851985@...il.com> wrote:

> > Instead, it calls irq_work() to do the event within a normal interrupt
> > context. Some architectures have the ability to trigger an interrupt on
> 
> irq_work processes event in normal interrupt context as you said but
> why interrupt context ? Is it because of the fast processing which is
> needed? Can we use softirq as anyways we have interrupt
> disabled(functions which calls irq_work makes sure of that right?).
> Hope I am not asking something very obvious.
>

We just need to make sure the work gets done outside of problem areas.
Usually, outside of locks, and specifically locks that disable
interrupts. Now, if irq_work() is needed outside of a lock that
only disables softirq, then you are correct, this would not be enough.
But really, because it's called "irq_work()" and not "softirq_work()",
you shouldn't be using locks that don't disable interrupts with a
irq_work handler.

Making it happen in softirq will just complicate the process. Real
interrupts are just easier to implement and suits the job well.

-- Steve
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