linux-kernel - Re: [Patch v4 14/16] x86, irq: Introduce helper to check whether an IOAPIC has been registered

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Wed, 10 Sep 2014 22:08:00 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Jiang Liu <jiang.liu@...ux.intel.com>
cc:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Randy Dunlap <rdunlap@...radead.org>,
	Yinghai Lu <yinghai@...nel.org>,
	Borislav Petkov <bp@...en8.de>,
	Grant Likely <grant.likely@...aro.org>, x86@...nel.org,
	Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
	Prarit Bhargava <prarit@...hat.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Tony Luck <tony.luck@...el.com>,
	Joerg Roedel <joro@...tes.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
	linux-acpi@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
	linux-pm@...r.kernel.org
Subject: Re: [Patch v4 14/16] x86, irq: Introduce helper to check whether an
 IOAPIC has been registered

On Wed, 10 Sep 2014, Jiang Liu wrote:
> On 2014/9/9 20:37, Thomas Gleixner wrote:
> >> +	ret  = mp_ioapic_registered(gsi_base);
> >> +	up_write(&acpi_ioapic_rwsem);
> >> +
> >> +	return ret;
> >> +}
> > 
> > So I assume that this is for a particular caller in the apci ioapic
> > hotplug code and that call site has its own serialization. Otherwise
> > the return value is not protected at all.
> > 
> > Please add a Docbook comment to that function, and document the
> > locking rules as thats pretty non obvious.
> How about this comments about locking rules?
> /*
>  * Locks related to IOAPIC hotplug
>  * Hotplug side:
>  *      ->lock_device_hotplug() //device_hotplug_lock
>  *              ->acpi_ioapic_rwsem
>  *                      ->ioapic_lock
>  * Interrupt mapping side:
>  *      ->acpi_ioapic_rwsem
>  *              ->ioapic_mutex
>  *                      ->ioapic_lock
>  */

That looks asymetric. Why is the hotplug side not taking ioapic_mutex?

Thanks,

	tglx
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/