Re: [PATCH v8 3/6] Uprobes: Support SDT markers having reference count (semaphore)

[Ravi Bangoria]

On 08/13/2018 06:47 PM, Oleg Nesterov wrote:
> On 08/13, Ravi Bangoria wrote:
>>
>>> But damn, process creation (exec) is trivial. We could add a new 
>>> uprobe_exec()
>>> hook and avoid delayed_uprobe_install() in uprobe_mmap().
>>
>> I'm sorry. I didn't get this.
> 
> Sorry for confusion...
> 
> I meant, if only exec*( could race with _register(), we could add another 
> uprobe
> hook which updates all (delayed) counters before return to user-mode.

Ok.

> 
>>> Afaics, the really problematic case is dlopen() which can race with 
>>> _register()
>>> too, right?
>>
>> dlopen() should internally use mmap() right? So what is the problem here? Can
>> you please elaborate.
> 
> What I tried to say is that we can't avoid 
> uprobe_mmap()->delayed_uprobe_install()
> because dlopen() can race with _register() too, just like exec.

Right :)

Thanks,
Ravi