Re: [PATCH RFC] util/error.c: Print backtrace on error

["Daniel P. Berrangé" <berrange@redhat.com>]

On Wed, Aug 06, 2025 at 12:34:23PM +0100, Daniel P. Berrangé wrote:
> On Wed, Aug 06, 2025 at 12:11:38PM +0100, Alex Bennée wrote:
> > Daniel P. Berrangé <berrange@redhat.com> writes:
> > 
> > > On Tue, Aug 05, 2025 at 07:57:38PM +0300, Manos Pitsidianakis wrote:
> > >> On Tue, Aug 5, 2025 at 7:49 PM Daniel P. Berrangé <berrange@redhat.com> wrote:
> > >> >
> > >> >
> > >> > Was there a specific place where you found things hard to debug
> > >> > from the error message alone ?  I'm sure we have plenty of examples
> > >> > of errors that can be improved, but wondering if there are some
> > >> > general patterns we're doing badly that would be a good win
> > >> > to improve ?
> > >> 
> > >> Some months ago I was debugging a MemoryRegion use-after-free and used
> > >> this code to figure out that the free was called from RCU context
> > >> instead of the main thread.
> > >
> > > We give useful names to many (but not neccessarily all) threads that we
> > > spawn. Perhaps we should call pthread_getname_np() to fetch the current
> > > thread name, and used that as a prefix on the error message we print
> > > out, as a bit of extra context ?
> > 
> > Do we always have sensible names for threads or only if we enable the
> > option?
> 
> I was surprised to discover we don't name threads by default, only if we
> add '-name debug-threads=yes'.  I'm struggling to understand why we would
> ever want thread naming disabled, if an OS supports it ?
> 
> I'm inclined to deprecate 'debug-threads' and always set the names when
> available.

FYI, I'm working on a small series that will enable thread names and
IDs to be printed by default with errors, and should post it sometime
this week.

With regards,
Daniel
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