linux-kernel - Re: [PATCH -rt] ide: fix interrupts processing issue with preempt-able hardirqs

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Date:	Wed, 25 Jun 2008 18:59:37 +0400
From:	Anton Vorontsov <avorontsov@...mvista.com>
To:	Sergei Shtylyov <sshtylyov@...mvista.com>
Cc:	Ingo Molnar <mingo@...e.hu>, linux-ide@...r.kernel.org,
	Bartlomiej Zolnierkiewicz <bzolnier@...il.com>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Steven Rostedt <rostedt@...dmis.org>,
	Daniel Walker <dwalker@...sta.com>
Subject: Re: [PATCH -rt] ide: fix interrupts processing issue with
	preempt-able hardirqs

On Wed, Jun 25, 2008 at 06:22:49PM +0400, Anton Vorontsov wrote:
> On Wed, Jun 25, 2008 at 05:15:43PM +0400, Sergei Shtylyov wrote:
> > Hello.
> >
> > Anton Vorontsov wrote:
> >
> >>>>> IDE interrupt handler relies on the fact that, if necessary, 
> >>>>> hardirqs will re-trigger on ISR exit. With fully preemtable IRQs 
> >>>>> this seems to be not true, since if hardirq thread is currently 
> >>>>> running, and the same IRQ raised again, then this IRQ will be 
> >>>>> simply lost.
> >
> >>>> actually no, that should not happen - if -rt loses an IRQ then 
> >>>> something broke in the threaded IRQ code. It's supposed to be a 
> >>>> drop-in, compatible IRQ flow with no driver changes needed.
> >
> >>> ..just as I thought, the bug somewhere deeper... heh.
> >
> >> Ok, a bit more investigation showed that this is indeed not RT specific
> >> per see, but issue emerges only on RT-style IRQ handlers + alim15x3 IDE
> >> controller (for example, PDC20269 works ok).
> >
> >    Does it happen only with ATAPI devices also or with ATA disks too?
> 
> So far I own two ATAPI devices, IDE disks are quire rare nowadays,
> should find one. ;-)
[...]
> >> Also, further testing showed that this issue isn't drive-specific, i.e.
> >> with a delay inserted before the unmask_irq(), the bug shows with any
> >> drive I have.
> >
> >    So, "shit happens" even with the ATA drives?
> 
> Will try as soon as I'll get one.

Thanks for the drive, and the result is:

hda: irq timeout: status=0x58 { DriveReady SeekComplete DataRequest }
ide: failed opcode was: unknown

-- 
Anton Vorontsov
email: cbouatmailru@...il.com
irc://irc.freenode.net/bd2
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