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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 15:36:57 +1100	[thread overview]
Message-ID: <20111212043657.GO14273@dastard> (raw)
In-Reply-To: <20111212023130.GI24062@one.firstfloor.org>

On Mon, Dec 12, 2011 at 03:31:30AM +0100, Andi Kleen wrote:
> > But that happens before do_IRQ is called, so what is the do_IRQ call
> > chain doing on this stack given that we've already supposed to have
> > switched to the interrupt stack before do_IRQ is called?
> 
> Not sure I understand the question.
> 
> The pt_regs are on the original stack (but they are quite small), all the rest 

It's ~180 bytes, so it's not really that small.

> is on the new stack. ISTs are not used for interrupts, only for 
> some special exceptions.

IST = ???

> do_IRQ doesn't switch any stacks on 64bit.

No, but it appears that it's caller does:

/* 0(%rsp): ~(interrupt number) */
        .macro interrupt func
        /* reserve pt_regs for scratch regs and rbp */
        subq $ORIG_RAX-RBP, %rsp
        CFI_ADJUST_CFA_OFFSET ORIG_RAX-RBP
        SAVE_ARGS_IRQ
        call \func
        .endm

and the SAVE_ARGS_IRQ macro switches to the per cpu interrupt stack.
The only caller does this:

common_interrupt:
        XCPT_FRAME
        addq $-0x80,(%rsp)              /* Adjust vector to [-256,-1] range */
        interrupt do_IRQ

So, why do we get this:

Dec  6 20:27:55 localhost kernel: <IRQ>  [<ffffffff81067097>] ?  warn_slowpath_common+0x87/0xc0
Dec  6 20:27:55 localhost kernel: [<ffffffff8106f6da>] ?  __do_softirq+0x11a/0x1d0
Dec  6 20:27:55 localhost kernel: [<ffffffff81067186>] ?  warn_slowpath_fmt+0x46/0x50
Dec  6 20:27:55 localhost kernel: [<ffffffff8100c2cc>] ?  call_softirq+0x1c/0x30
Dec  6 20:27:55 localhost kernel: [<ffffffff8100dfcf>] ?  handle_irq+0x8f/0xa0
Dec  6 20:27:55 localhost kernel: [<ffffffff814e310c>] ? do_IRQ+0x6c/0xf0
Dec  6 20:27:55 localhost kernel: [<ffffffff8100bad3>] ?  ret_from_intr+0x0/0x11
Dec  6 20:27:55 localhost kernel: <EOI>  [<ffffffff8115b80f>] ?  kmem_cache_free+0xbf/0x2b0

at the top of the stack frame? Is the stack unwinder walking back
across the interrupt stack to the previous task stack?

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 15:36:57 +1100	[thread overview]
Message-ID: <20111212043657.GO14273@dastard> (raw)
In-Reply-To: <20111212023130.GI24062@one.firstfloor.org>

On Mon, Dec 12, 2011 at 03:31:30AM +0100, Andi Kleen wrote:
> > But that happens before do_IRQ is called, so what is the do_IRQ call
> > chain doing on this stack given that we've already supposed to have
> > switched to the interrupt stack before do_IRQ is called?
> 
> Not sure I understand the question.
> 
> The pt_regs are on the original stack (but they are quite small), all the rest 

It's ~180 bytes, so it's not really that small.

> is on the new stack. ISTs are not used for interrupts, only for 
> some special exceptions.

IST = ???

> do_IRQ doesn't switch any stacks on 64bit.

No, but it appears that it's caller does:

/* 0(%rsp): ~(interrupt number) */
        .macro interrupt func
        /* reserve pt_regs for scratch regs and rbp */
        subq $ORIG_RAX-RBP, %rsp
        CFI_ADJUST_CFA_OFFSET ORIG_RAX-RBP
        SAVE_ARGS_IRQ
        call \func
        .endm

and the SAVE_ARGS_IRQ macro switches to the per cpu interrupt stack.
The only caller does this:

common_interrupt:
        XCPT_FRAME
        addq $-0x80,(%rsp)              /* Adjust vector to [-256,-1] range */
        interrupt do_IRQ

So, why do we get this:

Dec  6 20:27:55 localhost kernel: <IRQ>  [<ffffffff81067097>] ?  warn_slowpath_common+0x87/0xc0
Dec  6 20:27:55 localhost kernel: [<ffffffff8106f6da>] ?  __do_softirq+0x11a/0x1d0
Dec  6 20:27:55 localhost kernel: [<ffffffff81067186>] ?  warn_slowpath_fmt+0x46/0x50
Dec  6 20:27:55 localhost kernel: [<ffffffff8100c2cc>] ?  call_softirq+0x1c/0x30
Dec  6 20:27:55 localhost kernel: [<ffffffff8100dfcf>] ?  handle_irq+0x8f/0xa0
Dec  6 20:27:55 localhost kernel: [<ffffffff814e310c>] ? do_IRQ+0x6c/0xf0
Dec  6 20:27:55 localhost kernel: [<ffffffff8100bad3>] ?  ret_from_intr+0x0/0x11
Dec  6 20:27:55 localhost kernel: <EOI>  [<ffffffff8115b80f>] ?  kmem_cache_free+0xbf/0x2b0

at the top of the stack frame? Is the stack unwinder walking back
across the interrupt stack to the previous task stack?

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

--
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  reply	other threads:[~2011-12-12  4:37 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 [this message]
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
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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