Re: [PATCH v5 06/10] Uprobes: Support SDT markers having reference count (semaphore)

From: Srikar Dronamraju
Date: Wed Jul 04 2018 - 05:17:33 EST


>
> I'm not sure if I get your concerns but let me try to explain what happens
> in such cases. please let me know if I misunderstood your point.
>
> 1. Install a probe using perf.
> # ./perf probe sdt_tick:loop2
>
>
>
> Does this explain your concerns?
>


No, this was not my concern.
My concern is with two users on the same USDT.
1. First user enables the probe point but doesn't increment the ref_cnt.
via uprobe_register

2. Second user tries to enable the probe point and also increments the
ref_cnt via uprobe_register_refctr.

3. If the second user now removes the probe point via uprobe_unregister.

4. What is the state of the ref_cnt?

--
Thanks and Regards
Srikar