Hi -
Jamie.Parsons (@UNKNOWN_DOMAIN :-() wrote:
> [...] There is still a bug in the system tap script as the exit
> value of functions is always returned as the same as the entry value
> to functions. [...]
This is an occasionally confusing aspect of systemtap .return probes.
As per the stapprobes man page and elsewhere, most $context variables
accessed from .return probes represent function *entry-time snapshots*.
Try instead use of the @entry() construct, which makes explicit
which values you wish to be entry-time evaluated, and which later.
probe module("sctp").function("sctp_process_init").return {
printf("sctp_process_init updates assoc %p peer rwnd to %d\n",
@entry($asoc),
@cast(@entry($asoc),"sctp_association")->peer->rwnd);
/* evaluated at .return time: ^^^^^^^^^^^^ */
}
(http://sourceware.org/PR14437 should make the @cast unnecessary
eventually.)
- FChE
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