why just the last stap command works?

[Frank Ch. Eigler]

hit201j <hit201j@gmail.com> writes:

> [...]

Those registration-error-negative-22 messages are due to the kernel
rejecting kprobes on the requested addresses.  It can do this for a
variety of reasons, including placement on unfavourable instructions
(like lock/synch ones), or resource constraints (memory shortage), or
blacklisting.  You might try disassembling the kernel code at the
stap-identified addresses to get a hint why the kernel might be saying
no to us.

.function probes place probes at the head of the function.  .statement
probes place them within the body, and different line numbers/addresses
can lead to different rejection criteria. 

- FChE