From: Dave Chinner <david@fromorbit.com>
To: Andi Kleen <andi@firstfloor.org>
Cc: Christoph Hellwig <hch@infradead.org>,
linux-mm@kvack.org,
"Ryan C. England" <ryan.england@corvidtec.com>,
xfs@oss.sgi.com
Subject: Re: XFS causing stack overflow
Date: Mon, 12 Dec 2011 20:00:33 +1100 [thread overview]
Message-ID: <20111212090033.GQ14273@dastard> (raw)
In-Reply-To: <20111212051311.GJ24062@one.firstfloor.org>
On Mon, Dec 12, 2011 at 06:13:11AM +0100, Andi Kleen wrote:
> > It's ~180 bytes, so it's not really that small.
>
> Quite small compared to what real code uses. And also fixed
> size.
>
> >
> > > is on the new stack. ISTs are not used for interrupts, only for
> > > some special exceptions.
> >
> > IST = ???
>
> That's a hardware mechanism on x86-64 to switch stacks
> (Interrupt Stack Table or somesuch)
>
> With ISTs it would have been possible to move the the pt_regs too,
> but the software mechanism is somewhat simpler.
>
> > at the top of the stack frame? Is the stack unwinder walking back
> > across the interrupt stack to the previous task stack?
>
> Yes, the unwinder knows about all the extra stacks (interrupt
> and exception stacks) and crosses them as needed.
>
> BTW I suppose it wouldn't be all that hard to add more stacks and
> switch to them too, similar to what the 32bit do_IRQ does.
> Perhaps XFS could just allocate its own stack per thread
> (or maybe only if it detects some specific configuration that
> is known to need much stack)
That's possible, but rather complex, I think.
> It would need to be per thread if you could sleep inside them.
Yes, we'd need to sleep, do IO, possibly operate within a
transaction context, etc, and a workqueue handles all these cases
without having to do anything special. Splitting the stack at a
logical point is probably better, such as this patch:
http://oss.sgi.com/archives/xfs/2011-07/msg00443.html
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
_______________________________________________
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WARNING: multiple messages have this Message-ID (diff)
From: Dave Chinner <david@fromorbit.com>
To: Andi Kleen <andi@firstfloor.org>
Cc: Christoph Hellwig <hch@infradead.org>,
linux-mm@kvack.org, xfs@oss.sgi.com,
"Ryan C. England" <ryan.england@corvidtec.com>
Subject: Re: XFS causing stack overflow
Date: Mon, 12 Dec 2011 20:00:33 +1100 [thread overview]
Message-ID: <20111212090033.GQ14273@dastard> (raw)
In-Reply-To: <20111212051311.GJ24062@one.firstfloor.org>
On Mon, Dec 12, 2011 at 06:13:11AM +0100, Andi Kleen wrote:
> > It's ~180 bytes, so it's not really that small.
>
> Quite small compared to what real code uses. And also fixed
> size.
>
> >
> > > is on the new stack. ISTs are not used for interrupts, only for
> > > some special exceptions.
> >
> > IST = ???
>
> That's a hardware mechanism on x86-64 to switch stacks
> (Interrupt Stack Table or somesuch)
>
> With ISTs it would have been possible to move the the pt_regs too,
> but the software mechanism is somewhat simpler.
>
> > at the top of the stack frame? Is the stack unwinder walking back
> > across the interrupt stack to the previous task stack?
>
> Yes, the unwinder knows about all the extra stacks (interrupt
> and exception stacks) and crosses them as needed.
>
> BTW I suppose it wouldn't be all that hard to add more stacks and
> switch to them too, similar to what the 32bit do_IRQ does.
> Perhaps XFS could just allocate its own stack per thread
> (or maybe only if it detects some specific configuration that
> is known to need much stack)
That's possible, but rather complex, I think.
> It would need to be per thread if you could sleep inside them.
Yes, we'd need to sleep, do IO, possibly operate within a
transaction context, etc, and a workqueue handles all these cases
without having to do anything special. Splitting the stack at a
logical point is probably better, such as this patch:
http://oss.sgi.com/archives/xfs/2011-07/msg00443.html
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
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next prev parent reply other threads:[~2011-12-12 9:00 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-12-08 18:03 XFS causing stack overflow Ryan C. England
2011-12-09 11:55 ` Christoph Hellwig
2011-12-09 11:55 ` Christoph Hellwig
2011-12-09 15:56 ` Ryan C. England
2011-12-09 15:56 ` Ryan C. England
2011-12-09 22:19 ` Dave Chinner
2011-12-09 22:19 ` Dave Chinner
[not found] ` <20111209221956.GE14273__25752.826271537$1323469420$gmane$org@dastard>
2011-12-10 19:52 ` Andi Kleen
2011-12-10 19:52 ` Andi Kleen
2011-12-10 22:13 ` Dave Chinner
2011-12-10 22:13 ` Dave Chinner
2011-12-11 0:00 ` Andi Kleen
2011-12-11 0:00 ` Andi Kleen
2011-12-11 23:05 ` Dave Chinner
2011-12-11 23:05 ` Dave Chinner
2011-12-12 2:31 ` Andi Kleen
2011-12-12 2:31 ` Andi Kleen
2011-12-12 4:36 ` Dave Chinner
2011-12-12 4:36 ` Dave Chinner
2011-12-12 5:13 ` Andi Kleen
2011-12-12 5:13 ` Andi Kleen
2011-12-12 9:00 ` Dave Chinner [this message]
2011-12-12 9:00 ` Dave Chinner
2011-12-12 13:43 ` Ryan C. England
2011-12-12 13:43 ` Ryan C. England
2011-12-12 22:47 ` Dave Chinner
2011-12-12 22:47 ` Dave Chinner
[not found] ` <20111209115513.GA19994__23079.9863501035$1323435203$gmane$org@infradead.org>
2011-12-09 19:53 ` Andi Kleen
2011-12-09 19:53 ` Andi Kleen
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