Re: Should glibc be fully reentrant? What do we allow interposed symbols to do?

[Will Newton <will.newton@linaro.org>]

On 23 October 2014 03:29, Carlos O'Donell <carlos@redhat.com> wrote:
> On 10/21/2014 06:47 PM, Roland McGrath wrote:
>> But the slippery slope concerns me most of all.
>
> Any function the user interposes acts as a synchronous interrupt on the
> runtime.
>
> It is my opinion that users expect to be able to call any routine in the
> runtime without caution unless we tell them otherwise.
>
> Given that dlopen locks are recursive, as are stdio locks, I propose we
> fully support this notion that users already believe exists.
>
> The alternative is that we don't support it and treat interposed functions
> as if they were in a signal handler context, only being allowed to call
> async-signal-safe functions, and we might as well remove the recursive
> support from the locks such that users get useful backtraces from deadlocks.
> It is my opinion that such a direction would not help our users and would
> not help the project.
>
> The similar situations we need to clarify are LD_AUDIT modules, and
> IFUNC resolvers, but let us proceed orderly one topic at a time.
>
> In summary
> ==========
>
> Allow interposed functions to call back into the runtime, and fix any
> places where this breaks.

Do you have a plan to fix dlsym similarly? ISTR that pretty reliably
trips on the same issue when used in a malloc hook.

-- 
Will Newton
Toolchain Working Group, Linaro