linux-kernel - Re: [PATCH v2 7/9] gpio: 104-idi-48: make use of raw

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Message-ID: <CACRpkdbqUmTHv7pyc+EVznzR8BiO_=pc12awsS4ygYJsbsG=EQ@mail.gmail.com>
Date:   Tue, 28 Mar 2017 11:11:59 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     William Breathitt Gray <vilhelm.gray@...il.com>
Cc:     Julia Cartwright <julia@...com>,
        Alexandre Courbot <gnurou@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        linux-rt-users@...r.kernel.org,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>
Subject: Re: [PATCH v2 7/9] gpio: 104-idi-48: make use of raw_spinlock variants

On Wed, Mar 22, 2017 at 1:44 PM, William Breathitt Gray
<vilhelm.gray@...il.com> wrote:
> On Tue, Mar 21, 2017 at 05:43:07PM -0500, Julia Cartwright wrote:
>>The 104-idi-48 gpio driver currently implements an irq_chip for handling
>>interrupts; due to how irq_chip handling is done, it's necessary for the
>>irq_chip methods to be invoked from hardirq context, even on a a
>>real-time kernel.  Because the spinlock_t type becomes a "sleeping"
>>spinlock w/ RT kernels, it is not suitable to be used with irq_chips.
>>
>>A quick audit of the operations under the lock reveal that they do only
>>minimal, bounded work, and are therefore safe to do under a raw spinlock.
>>
>>Signed-off-by: Julia Cartwright <julia@...com>
>
> Hi Julia,
>
> This driver also uses a second spinlock_t, called ack_lock, to prevent
> reentrance into the idi_48_irq_handler function. Should ack_lock also be
> implemented as a raw_spinlock_t?

Hm, can I apply this one patch or not?

Linus Walleij