From: Alan <alan@lxorguk.ukuu.org.uk>
To: Tejun Heo <htejun@gmail.com>
Cc: albertl@mail.com, albertcc@tw.ibm.com,
Jeff Garzik <jeff@garzik.org>,
Linux IDE <linux-ide@vger.kernel.org>,
Mark Lord <mlord@pobox.com>,
matthieu castet <castet.matthieu@free.fr>,
Tobias Powalowski <t.powa@gmx.de>
Subject: Re: [PATCH] libata: waits up to 10 microseconds for early irq problem
Date: Tue, 28 Nov 2006 10:46:59 +0000 [thread overview]
Message-ID: <20061128104659.4ec91296@localhost.localdomain> (raw)
In-Reply-To: <456C0F11.30301@gmail.com>
> > The IRQ delivery is async to the I/O so this makes a lot of sense for all
> > cases.
>
> I don't think that's true unless the controller is doing something funky
> as in SET XFERMODE. Can you enlighten me?
It is true for all cases. There is no synchronization between interrupt
delivery and I/O cycles and both of them are asynchronous. It is
especially obvious on older APIC based boxes that use a 4 wire bus to
send interrupt messages around.
This leads to suprising sequences like
device raises IRQ
kernel blocks device IRQ at chip
kernel reads to post the block
kernel does other stuff
IRQ message finally arrives
IRQ taken
next prev parent reply other threads:[~2006-11-28 10:40 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <200611180759.34622.t.powa@gmx.de>
[not found] ` <20061118002357.564dbb9d.akpm@osdl.org>
2006-11-18 21:20 ` possibility to merge via_pata fixes to .19 stable series? Jeff Garzik
2006-11-18 22:43 ` Alan
2006-11-19 3:07 ` Andrew Morton
2006-11-19 5:34 ` Tejun Heo
2006-11-19 6:02 ` Andrew Morton
2006-11-28 6:52 ` [PATCH] libata: waits up to 10 microseconds for early irq problem Albert Lee
2006-11-28 10:25 ` Alan
2006-11-28 10:27 ` Tejun Heo
2006-11-28 10:46 ` Alan [this message]
2006-11-28 14:00 ` Mark Lord
2006-11-28 14:12 ` Alan
2006-11-28 14:16 ` Mark Lord
2006-11-28 11:32 ` Albert Lee
2006-11-28 14:17 ` Albert Lee
2006-11-28 14:42 ` Mark Lord
2006-11-28 19:13 ` Jeff Garzik
2006-11-30 9:43 ` [PATCH] libata: blacklist " Albert Lee
2006-11-30 11:29 ` Alan
2006-11-30 20:37 ` Mark Lord
2006-11-30 20:45 ` Mark Lord
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