linux-kernel - Re: KGDB fails to pass selft tests on x86-64 (v2.6.26)

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Date:	Thu, 24 Jul 2008 21:05:17 +0200
From:	"Vegard Nossum" <vegard.nossum@...il.com>
To:	"Jason Wessel" <jason.wessel@...driver.com>
Cc:	"Francis Moreau" <francis.moro@...il.com>,
	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>
Subject: Re: KGDB fails to pass selft tests on x86-64 (v2.6.26)

On Thu, Jul 24, 2008 at 4:55 PM, Jason Wessel
<jason.wessel@...driver.com> wrote:
> It is not likely that CONFIG_DEBUG_RODATA can have any impact because
> the boot test occurs before the text sections are marked read-only.  A
> hang in this section indicates a conflict where something is spinning
> for a lock in the NMI handler, or the NMI handler re-entered and tried
> to acquire another lock.
>
> In the 2.6.26 time frame I found and fixed at least one defect around
> updating the clock while in the NMI which required that you not do it
> from the NMI context.  It sounds as if there is yet another problem
> along these lines, and of course it is a timing race...

I just got another one now, with HEAD at
f0766440dda7ace8a43b030f75e2dcb82449fb85:

calling  init_kgdbts+0x0/0x20
kgdb: Registered I/O driver kgdbts.
kgdbts:RUN plant and detach test
kgdbts:RUN sw breakpoint test
kgdbts:RUN bad memory access test
kgdbts:RUN singlestep test 1000 iterations
kgdbts:RUN singlestep [0/1000]
kgdbts:RUN singlestep [100/1000]
kgdbts:RUN singlestep [200/1000]
kgdbts:RUN singlestep [300/1000]
kgdbts:RUN singlestep [400/1000]
kgdbts:RUN singlestep [500/1000]
kgdbts:RUN singlestep [600/1000]

Full stop. But the commit has timestamp May 9, 2008, so maybe you
fixed it after that.


Vegard

-- 
"The animistic metaphor of the bug that maliciously sneaked in while
the programmer was not looking is intellectually dishonest as it
disguises that the error is the programmer's own creation."
	-- E. W. Dijkstra, EWD1036
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