linux-kernel - Re: preempt.h: some SOFTIRQ_OFFSET should be SOFTIRQ

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Message-ID: <20190213040539.GA8524@lenoir>
Date:   Wed, 13 Feb 2019 05:05:40 +0100
From:   Frederic Weisbecker <frederic@...nel.org>
To:     Denys Vlasenko <vda.linux@...glemail.com>
Cc:     Frederic Weisbecker <fweisbec@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: preempt.h: some SOFTIRQ_OFFSET should be SOFTIRQ_MASK?

On Tue, Feb 05, 2019 at 07:34:31PM +0100, Denys Vlasenko wrote:
> SOFTIRQ is a counter.
> Why here:
> 
> #define in_serving_softirq()    (softirq_count() & SOFTIRQ_OFFSET)
> #define in_task()               (!(preempt_count() & \
>                                    (NMI_MASK | HARDIRQ_MASK | SOFTIRQ_OFFSET)))
> 
> we check only lowest bit?

So we have SOFTIRQ_OFFSET that is used when serving softirqs.
And we have SOFTIRQ_DISABLE_OFFSET that is used when we disable
softirqs.

I think the choice is right on both tests above, or am I missing something?