[PATCH] Avoid deadlock in malloc on backtrace

[Carlos O'Donell]

On 03/02/2015 12:57 PM, Mike Frysinger wrote:
> to be clear, while i support adding an optional "paranoid" mode, i'm entirely 
> against disabling them by default.  these crash messages have improved the lives 
> of users and developers significantly since they were added.  i don't have data 
> to back this claim up, but having worked as a developer writing my own code, 
> an upstream developer releasing my own packages, and a distro maintainer on a 
> wide swath of packages, all continuously since the glibc 2.2.5 days, i think my 
> anecdotal memory is sufficient.  as a maintainer of the toolchain, i certainly 
> know it helps bucket bugs -- before this message, most random crashes were 
> thrown at the toolchain distro maintainers (after all, a crash in malloc must 
> surely be the fault of the C library).  now with all the memory corruption 
> hooks, we've got a pretty strong/reliable signal that it is entirely the fault 
> of the package.  returning to that status quo would be a terrible idea.
> 
> if a distro has frameworks in place to replace the functionality of these (e.g. 
> a core dump handler), then they can make the decision to also opt in their C 
> library to this mode.  on Gentoo, we make the decision based on how hardened the 
> user wants their system.

That's a very cogent argument for keeping the status-quo behaviour and fixing
the deadlock, while continuing the discussion over what exactly should be done.

Cheers,
Carlos.