osmocom
/
libosmocore
mirror of https://gerrit.osmocom.org/libosmocore
11
0
Fork 0
Code Issues Releases Wiki Activity

fsm: term: safer iteration to remove all child FSMs 

When terminating child FSMs, restart iteration after every child, to make
sure that we don't terminate a child twice. Terminating one child may emit
events that in turn terminates other children.

I created this patch because at first it looked like the cause of a bug,
which turned out not to be the case. So I have no actual use case of this
situation, but it does generally make sense to me, so submitting this.

Change-Id: I00990b47e42eeb43707a9a42abcd9df52fe5f483
This commit is contained in:
Neels Hofmeyr 2016-12-20 12:05:19 +01:00
parent 42b59c1bf0
commit 06ac9b40ed
1 changed files with 20 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

24
src/fsm.c
View File

@ -427,17 +427,33 @@ void _osmo_fsm_inst_term(struct osmo_fsm_inst *fi,
enum osmo_fsm_term_cause cause, void *data,
const char *file, int line)
{
struct osmo_fsm_inst *child, *child2;
struct osmo_fsm_inst *first_child, *last_seen_first_child;
struct osmo_fsm_inst *parent = fi->proc.parent;
uint32_t parent_term_event = fi->proc.parent_term_event;
LOGPFSMSRC(fi, file, line, "Terminating (cause = %s)\n",
osmo_fsm_term_cause_name(cause));
/* iterate over all children */
llist_for_each_entry_safe(child, child2, &fi->proc.children, proc.child) {
/* iterate over all children, starting from the beginning every time:
* terminating an FSM may emit events that cause other FSMs to also
* terminate and remove themselves from this list. */
last_seen_first_child = NULL;
while (!llist_empty(&fi->proc.children)) {
first_child = llist_entry(fi->proc.children.next,
typeof(*first_child),
proc.child);
/* paranoia: do not loop forever */
if (first_child == last_seen_first_child) {
LOGPFSMLSRC(fi, LOGL_ERROR, file, line,
"Internal error while terminating child"
" FSMs: a child FSM is stuck\n");
break;
}
last_seen_first_child = first_child;
/* terminate child */
_osmo_fsm_inst_term(child, OSMO_FSM_TERM_PARENT, NULL,
_osmo_fsm_inst_term(first_child, OSMO_FSM_TERM_PARENT, NULL,
file, line);
}