Re: [Crash-utility] mount cmd crashes crash

Wednesday, 18 August 2010

Sorry, forgot to reply all:
---------------------------

On Wed, 2010-08-18 at 20:57 +0000, Dave Anderson wrote:
...
 ----- "Bob Montgomery" <bob.montgomery(a)hp.com&gt;
wrote:

 > I'm working on a dump of a system that did not have a PID 1.  I don't
...
 > think it's relevant to the crash itself, but it does cause
crash get
 > a seg fault. 
...
 > 
 > I don't know if it was important to have the context of pid 1 for
 > reporting mounts, or just any context, but this hack makes the problem
...
 > go away, although not a very efficient way to find the lowest
existing
...
 > PID above 0.  

 Yeah, it's not important to use the context of pid 1, but it just needs
...
 some context, and I had presumed that init would always exist.  I
thought
...
 that the panic("Attempted to kill the idle task!") in
do_exit() would
 prevent pid 1 from ever going away -- but apparently your kernel figured
...
 out how to do it elsewhere...  ;-) 
That test is for PID 0, not PID 1 (at least on the kernel I'm
debugging.)  However, there is this also:

        if (unlikely(tsk == child_reaper))
                panic("Attempted to kill init!");

And child_reaper in the dump points to a task struct for init that isn't
in the ps listing.  Hmmm.  Maybe that part *is* interesting in this
dump...

...

 Your patch would pick a kernel thread pid, and apparently everything still
...
 works OK?  That being the case, it's fine with me. 
With the patch, these commands all produce the same output:
crash-5.0.6-fix> mount >mount.out
crash-5.0.6-fix> mount -n 2 >mount2.out
crash-5.0.6-fix> mount -n 1459 >mount1459.out

I discovered the -n option as my first workaround.

Bob M.

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