LIBC_PROBE and locks

[Florian Weimer]

On 11/17/2015 05:20 AM, Carlos O'Donell wrote:
> On 11/16/2015 12:54 PM, Florian Weimer wrote:
>> Is it okay to call LIBC_PROBE while internal locks are held?  Or could
>> this result in deadlocks by itself?  (I'm aware that the arguments are
>> always evaluated.)
> 
> How would it cause deadlocks? The external observer, say systemtap or
> gdb, are outside of the process and should not modify the state of the
> process in such a way as to cause a deadlock. Under what conditions might
> the evaluation of the arguments cause a deadlock?

Are only external observers supported?  I wasn't sure if this is some
sort of self-observing capability which is supposed to work, in which
case this would be some sort of callback mechanism and subject to
similar locking issues.

Frank tells me that self-inspection isn't supported, so my concern is
unfounded.

Florian