Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Wed, 13 Feb 2019 05:05:40 +0100
From:   Frederic Weisbecker <frederic@kernel.org>
To:     Denys Vlasenko <vda.linux@googlemail.com>
Cc:     Frederic Weisbecker <fweisbec@gmail.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: preempt.h: some SOFTIRQ_OFFSET should be SOFTIRQ_MASK?
Message-ID: <20190213040539.GA8524@lenoir>
References: <CAK1hOcN8_0MNEFfoHg0sAuu09SPhXHvXfXkeHONtoFXOArjumg@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CAK1hOcN8_0MNEFfoHg0sAuu09SPhXHvXfXkeHONtoFXOArjumg@mail.gmail.com>
User-Agent: Mutt/1.9.4 (2018-02-28)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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?