linux-kernel - Re: Interrupts are being dropped under heavy IO on -rt .

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]

Message-ID: <alpine.LFD.2.00.0904102357470.21577@localhost.localdomain>
Date:	Fri, 10 Apr 2009 23:59:48 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	jvrao <jvrao@...ux.vnet.ibm.com>
cc:	LKML <linux-kernel@...r.kernel.org>,
	rt-users <linux-rt-users@...r.kernel.org>,
	Mike Anderson <andmike@...ux.vnet.ibm.com>,
	"Luis Claudio R. Goncalves" <lgoncalv@...hat.com>,
	linux-driver@...gic.com
Subject: Re: Interrupts are being dropped under heavy IO on -rt .

On Fri, 10 Apr 2009, jvrao wrote:
> Qlogic driver uses MSI-EDGE interrupts by default.
> 
> On -rt kernel under heavy IO load we observed that the driver missed
> interrupts occasionally.
> 
> Missing interrupts caused spurious mailbox timeouts and path failovers.
> 
> Suspecting MSI interrupts, we disabled MSI and forcing the driver to use APIC
> interrupts (Patch attached).
> 
> With this change, our IO tests ran for extended period of time without any
> issues.
> 
> It would be interesting to see if the MSI infrastructure itself has issues on
> realtime, or it is the combination of qla2xxx/MSI.
> 
> Right now we don't have any setup to test out MSI with other adapters. Hence,
> wondering if anyone faced similar issues.

Hmm. Can we get down to the root cause of that problem instead of
applying a bandaid patch ?

If -rt has problems with MSI edge interrupts then we really need to
figure out why. If the qlogic driver has problems with the different
timings of -rt then we need to fix that one.

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/