Re: [PATCH] Remove deprecated IRQF_DISABLED flag entirely

From: Valentin Rothberg <valentinrothberg@gmail.com>
To: Hannes Reinecke <hare@suse.de>
Cc: akpm@linux-foundation.org, Jonathan Corbet <corbet@lwn.net>,
	Ralf Baechle <ralf@linux-mips.org>,
	David Woodhouse <dwmw2@infradead.org>,
	Brian Norris <computersforpeace@gmail.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Paul Bolle <pebolle@tiscali.nl>, Jiri Kosina <jkosina@suse.cz>,
	Ewan Milne <emilne@redhat.com>, Christoph Hellwig <hch@lst.de>,
	Huacai Chen <chenhc@lemote.com>, Hongliang Tao <taohl@lemote.com>,
	Nishanth Menon <nm@ti.com>,
	Santosh Shilimkar <santosh.shilimkar@ti.com>,
	Peter Ujfalusi <peter.ujfalusi@ti.com>,
	Tony Lindgren <tony@atomide.com>, Rajendra Nayak <rnayak@ti.com>,
	Sricharan R <r.sricharan@ti.com>, Afzal Mohammed <afzal@ti.com>,
	Keerthy <j-keerthy@ti.com>,
	Dan Carpenter <dan.carpenter@oracle.com>,
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	Randy Dunlap <rdunlap@infradead.org>,
	Kukjin Kim <kgene.kim@samsung.com>,
	"Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
	Quentin Lambert <lambert.quentin@gmail.com>,
	Eyal Perry <eyalpe@mellanox.com>, Arnd Bergmann <arnd@arndb.de>,
	Peter Zijlstra <peterz@infradead.org>,
	linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-mips@linux-mips.org, iss_storagedev@hp.com,
	linux-mtd@lists.infradead.org, linux-usb@vger.kernel.org
Subject: Re: [PATCH] Remove deprecated IRQF_DISABLED flag entirely
Date: Thu, 5 Mar 2015 14:41:03 +0100	[thread overview]
Message-ID: <CAD3Xx4K+ewe3RK479J_Vsm69pC3NO4q-u76Xy5L6Ps=FjVcQrw@mail.gmail.com> (raw)
In-Reply-To: <54F855E4.9030106@suse.de>

On Thu, Mar 5, 2015 at 2:11 PM, Hannes Reinecke <hare@suse.de> wrote:
> On 03/05/2015 01:59 PM, Valentin Rothberg wrote:
>> The IRQF_DISABLED is a NOOP and has been scheduled for removal since
>> Linux v2.6.36 by commit 6932bf37bed4 ("genirq: Remove IRQF_DISABLED from
>> core code").
>>
>> According to commit e58aa3d2d0cc ("genirq: Run irq handlers with
>> interrupts disabled") running IRQ handlers with interrupts enabled can
>> cause stack overflows when the interrupt line of the issuing device is
>> still active.
>>
>> This patch ends the grace period for IRQF_DISABLED (i.e., SA_INTERRUPT
>> in older versions of Linux) and removes the definition and all remaining
>> usages of this flag.
>>
>> Signed-off-by: Valentin Rothberg <valentinrothberg@gmail.com>
>> ---
>> The bigger hunk in Documentation/scsi/ncr53c8xx.txt is removed entirely
>> as IRQF_DISABLED is gone now; the usage in older kernel versions
>> (including the old SA_INTERRUPT flag) should be discouraged.  The
>> trouble of using IRQF_SHARED is a general problem and not specific to
>> any driver.
>>
>> I left the reference in Documentation/PCI/MSI-HOWTO.txt untouched since
>> it has already been removed in linux-next by commit b0e1ee8e1405
>> ("MSI-HOWTO.txt: remove reference on IRQF_DISABLED").
>>
>> All remaining references are changelogs that I suggest to keep.
>
> While you're at it: having '0x0' as a value for the irq flags looks
> a bit silly, and makes you wonder what the parameter is for.
>
> I would rather like to have
>
> #define IRQF_NONE 0x0
>
> and use it for these cases.
> That way the scope of that parameter is clear.

I like the idea.  I checked the source code for such cases and passing
0 or 0x0 as IRQ flags appears quite often (also in the devm
counterparts).
If nobody is against your proposal, then I will prepare a Coccinelle
script that takes care of it and send it in  a patch series (e.g.,
introduce definition of IRQF_NONE, the Coccinelle and following a big
patch that applies changes proposed by the script).

Kind regards,
 Valentin