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Date: Sun, 17 Feb 2013 19:17:09 +0100
Message-ID: <CAFTL4hyBm8AH4UKyN2VaRb4yBt7C4rG1ETQ3qXvNUdbh5HzSng@mail.gmail.com>
Subject: Re: Debugging Thinkpad T430s occasional suspend failure.
From: Frederic Weisbecker <fweisbec@gmail.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>, Dave Jones <davej@redhat.com>,
        Hugh Dickins <hughd@google.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Paul McKenney <paul.mckenney@linaro.org>
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2013/2/17 Linus Torvalds <torvalds@linux-foundation.org>:
> On Sun, Feb 17, 2013 at 7:11 AM, Frederic Weisbecker <fweisbec@gmail.com> wrote:
>>
>> preempt_value_in_interrupt() looks buggy in your patch: it makes
>> invoke_softirq() returning if (val & HARDIRQ_MASK). But that's always
>> true since you have moved further the sub_preempt_count(IRQ_EXIT)
>> further.
>
> No, that's not it. The value hasn't been written back yet, but it already did:
>
> +       int offset = IRQ_EXIT_OFFSET;
> +       int count = preempt_count() - offset;
>
> so the 'count' has the IRQ_EXIT_OFFSET already subtracted. So no,
> HARDIRQ_MASK is *not* always set.

Ah right. I was confused.