[sheepdog] [PATCH] util: dump ucontext in crash handlers

[Hitoshi Mitake]

At Thu, 09 May 2013 00:19:12 +0900,
MORITA Kazutaka wrote:
> 
> At Mon, 06 May 2013 22:38:21 +0900,
> Hitoshi Mitake wrote:
> > 
> > At Wed, 01 May 2013 22:21:16 +0900,
> > MORITA Kazutaka wrote:
> > > 
> > > At Wed,  1 May 2013 18:30:56 +0900,
> > > Hitoshi Mitake wrote:
> > > > 
> > > > Current crash handlers (of sheep, collie, and logger) don't dump
> > > > register status when the signal rises. This patch let them dump the
> > > > information. I believe especially RIP is useful for debugging.
> > > 
> > > I don't thinks so.  If you are debugging Sheepdog on your environment,
> > > you can get the register values from the core file.  If you are
> > > debugging with a reported sheep.log from other environment, how does
> > > the register status help us?
> > > 
> > > I cannot image the use case of RIP, too.  We can know where the
> > > process crashed from the backtrace.  Why do we need it?
> > 
> > Sorry for my slack description. Sometimes I debug programs with
> > objdump -d, so contents of registers are informative for me. But this
> > is not a productive way and I should switch to gdb.
> > 
> > But dumping registers is helpful for users. Because core files might
> > contain sensitive information (potentially) so in some cases sending
> > core files to public mailing lists would not be allowed. Contents of
> > registers would be helpful for such a case. e.g. redis employes this
> > way: http://antirez.com/news/43
> > (Of course redis is a on memory storage software and it stores almost
> > every data on main memory. So core files produced by redis must be
> > more sensitive than ones produced by sheep. But the core files
> > produced by sheep would also contain sensitive information.)
> 
> NACK, the register status in the bug report doesn't help us unless we share the
> same executable binary file.  In addition, debugging with the register status is
> a pain.  I'd suggest adding more sd_printf() if you are trying to fix a problem
> which needs register information.

OK, I agree.

Thanks,
Hitoshi