Re: Segmentation fault with drgn + libkdumpfile

On Wed, 10 Jan 2024 11:48:22 -0800
Stephen Brennan <[email protected]> wrote:

> Petr Tesařík <[email protected]> writes:
>[...]
> > I was able to write a test case for the NULL data pointer. The bug
> > should be fixed by commit e63dab40c8cefdfc013dc57915de9852dbb283e4.
> >
> > Stephen, can you rebuild and verify with your dump file that this was
> > indeed the same bug?  
> 
> Hi Petr,
> 
> I went ahead and pulled the latest from tip and ran my reproducer. The
> segmentation fault is indeed gone!

Great!

> I tested c10036e ("cache: Optimize data reclaim for missed entries"), to
> be exact, which contains e63dab4 as well.

I spent some time pondering whether the other call of reinit_entry() is
also affected. But it's not, so this other commit should be a no-op.

> Thank you so much for taking the time to go back & forth with me on this
> one! I suppose there's a reason that caching is one of the two hard
> problems in computer science ;)

Given that the relevant counter was decremented, it may also be seen as
an off-by-one bug. I think it's all a matter of naming things...

> I owe you a beverage of your choice next time we see each other!

Beer if in Europe, bourbon if in the US. Thanks. ;-)

Petr T