[vbox-dev] OSE r32797 causes null-pointer dereference on linux host

[Frank Mehnert]

Walt,

On Friday 08 October 2010, walt wrote:
> On 10/07/2010 09:04 AM, Frank Mehnert wrote:
> > On Wednesday 06 October 2010, walt wrote:
> >> My amd64 machine doesn't print anything at all, but syslog on my
> >> x86 is included below.  It makes sense that the offending code has
> >> to do with timers because GVMM_SCHED_WITH_PPT is the only thing
> >> changed by r32797.
> >
> > I have a tickless system here as well and currently running
> > Linux 2.6.36-rc7. Could you check if the problem persists if
> > you update to this version? And please make sure to update the
> > VBox source code to r32985 or later.
>
> Okay, I'm up to date with r32986 and 2.6.36-rc7.  Alas, I see the same
> behavior -- instant lockup on the amd64x2 with no messages on the console
> or in syslog, but the amd32 linux host survives the VBox crash and prints
> the same syslog I posted yesterday.

Ok, thanks for the test. Could you attach your kernel config
(compress please)?

> The critical lines of code involved:
>
> #if defined(RT_OS_LINUX) || defined(DOXYGEN_RUNNING)
> /** Define this to enable the periodic preemption timer. */
> # define GVMM_SCHED_WITH_PPT
> #endif

This code enables a new mechanism which causes the problem on your
kernel.

> Is DOXYGEN_RUNNING referring to the documentation system of the same
> name?  I ask only because I used the --disable-docs configure flag on
> both machines because I didn't want to install the entire latex system
> just to generate the user manual.

DOXYGEN_RUNNING is only defined while doxygen is is processing the
source files. The DOXYGEN_RUNNING is not related to this problem.

> However, the test for RT_OS_LINUX is the recent addition that tickles
> this bug by setting GVMM_SCHED_WITH_PPT to TRUE.  If I delete the test
> for RT_OS_LINUX, the crash disappears.

That is to be expected as written above. When you disable this define
you disable the new code.

> BTW, what does the 'RT' mean?

'runtime' ... (_not_ realtime!)

Kind regards,

Frank
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