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tevent: Clarify apparently useless conditions

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Comment on two similar conditions in tevent_standard.c, which,
otherwise, at a first glance, seem useless, i.e. always true.

The conditions checking glue->epoll_ops for being non-NULL, imply that
it *can* be NULL. A casual reader would not generally expect a "member"
function to modify its container's pointer in a container higher up, and
would assume that glue->epoll_ops could be NULL before the call,
resulting in a near-NULL pointer dereference.

However, in this case epoll_ops is indeed cleared in those "member"
functions, in the case of an epoll interface failure, to signify
fallback to poll interface.

Reviewed-by: Jeremy Allison <jra@samba.org>
Reviewed-by: Uri Simchoni <uri@samba.org>

Autobuild-User(master): Uri Simchoni <uri@samba.org>
Autobuild-Date(master): Tue Jul 12 13:56:41 CEST 2016 on sn-devel-144
This commit is contained in:
Nikolai Kondrashov 2016-06-29 15:05:08 +03:00 committed by Uri Simchoni
parent 792f89cdb6
commit 9d29593d92
1 changed files with 10 additions and 0 deletions
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10
lib/tevent/tevent_standard.c
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@ -112,6 +112,11 @@ static int std_event_loop_once(struct tevent_context *ev, const char *location)
int ret;
ret = glue->epoll_ops->loop_once(ev, location);
/*
* If the above hasn't panicked due to an epoll interface failure,
* std_fallback_to_poll() wasn't called, and hasn't cleared epoll_ops to
* signify fallback to poll_ops.
*/
if (glue->epoll_ops != NULL) {
/* No fallback */
return ret;
@ -138,6 +143,11 @@ static int std_event_loop_wait(struct tevent_context *ev, const char *location)
int ret;
ret = glue->epoll_ops->loop_wait(ev, location);
/*
* If the above hasn't panicked due to an epoll interface failure,
* std_fallback_to_poll() wasn't called, and hasn't cleared epoll_ops to
* signify fallback to poll_ops.
*/
if (glue->epoll_ops != NULL) {
/* No fallback */
return ret;