Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933703AbdCVMvb (ORCPT ); Wed, 22 Mar 2017 08:51:31 -0400 Received: from mail-yw0-f193.google.com ([209.85.161.193]:35290 "EHLO mail-yw0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759041AbdCVMvV (ORCPT ); Wed, 22 Mar 2017 08:51:21 -0400 Date: Wed, 22 Mar 2017 08:44:14 -0400 From: William Breathitt Gray To: Julia Cartwright Cc: Linus Walleij , Alexandre Courbot , linux-kernel@vger.kernel.org, linux-rt-users@vger.kernel.org, linux-gpio@vger.kernel.org Subject: Re: [PATCH v2 7/9] gpio: 104-idi-48: make use of raw_spinlock variants Message-ID: <20170322124414.GA22323@sophia> References: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.7.2 (2016-11-26) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3174 Lines: 97 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 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? Thanks, William Breathitt Gray >--- >New patch as of v2 of series. > > drivers/gpio/gpio-104-idi-48.c | 18 ++++++++++-------- > 1 file changed, 10 insertions(+), 8 deletions(-) > >diff --git a/drivers/gpio/gpio-104-idi-48.c b/drivers/gpio/gpio-104-idi-48.c >index 568375a7ebc2..337c048168d8 100644 >--- a/drivers/gpio/gpio-104-idi-48.c >+++ b/drivers/gpio/gpio-104-idi-48.c >@@ -51,7 +51,7 @@ MODULE_PARM_DESC(irq, "ACCES 104-IDI-48 interrupt line numbers"); > */ > struct idi_48_gpio { > struct gpio_chip chip; >- spinlock_t lock; >+ raw_spinlock_t lock; > spinlock_t ack_lock; > unsigned char irq_mask[6]; > unsigned base; >@@ -112,11 +112,12 @@ static void idi_48_irq_mask(struct irq_data *data) > if (!idi48gpio->irq_mask[boundary]) { > idi48gpio->cos_enb &= ~BIT(boundary); > >- spin_lock_irqsave(&idi48gpio->lock, flags); >+ raw_spin_lock_irqsave(&idi48gpio->lock, flags); > > outb(idi48gpio->cos_enb, idi48gpio->base + 7); > >- spin_unlock_irqrestore(&idi48gpio->lock, flags); >+ raw_spin_unlock_irqrestore(&idi48gpio->lock, >+ flags); > } > > return; >@@ -145,11 +146,12 @@ static void idi_48_irq_unmask(struct irq_data *data) > if (!prev_irq_mask) { > idi48gpio->cos_enb |= BIT(boundary); > >- spin_lock_irqsave(&idi48gpio->lock, flags); >+ raw_spin_lock_irqsave(&idi48gpio->lock, flags); > > outb(idi48gpio->cos_enb, idi48gpio->base + 7); > >- spin_unlock_irqrestore(&idi48gpio->lock, flags); >+ raw_spin_unlock_irqrestore(&idi48gpio->lock, >+ flags); > } > > return; >@@ -186,11 +188,11 @@ static irqreturn_t idi_48_irq_handler(int irq, void *dev_id) > > spin_lock(&idi48gpio->ack_lock); > >- spin_lock(&idi48gpio->lock); >+ raw_spin_lock(&idi48gpio->lock); > > cos_status = inb(idi48gpio->base + 7); > >- spin_unlock(&idi48gpio->lock); >+ raw_spin_unlock(&idi48gpio->lock); > > /* IRQ Status (bit 6) is active low (0 = IRQ generated by device) */ > if (cos_status & BIT(6)) { >@@ -256,7 +258,7 @@ static int idi_48_probe(struct device *dev, unsigned int id) > idi48gpio->chip.get = idi_48_gpio_get; > idi48gpio->base = base[id]; > >- spin_lock_init(&idi48gpio->lock); >+ raw_spin_lock_init(&idi48gpio->lock); > spin_lock_init(&idi48gpio->ack_lock); > > err = devm_gpiochip_add_data(dev, &idi48gpio->chip, idi48gpio); >-- >2.12.0 >