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sd-event: rebreak comments

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This commit is contained in:
Yu Watanabe 2022-04-09 08:23:50 +09:00
parent d89e18cc38
commit 91c700713f
1 changed files with 22 additions and 31 deletions
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53
src/libsystemd/sd-event/sd-event.c
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@ -3218,23 +3218,16 @@ static int process_child(sd_event *e, int64_t threshold, int64_t *ret_min_priori
e->need_process_child = false;
/*
So, this is ugly. We iteratively invoke waitid() with P_PID
+ WNOHANG for each PID we wait for, instead of using
P_ALL. This is because we only want to get child
information of very specific child processes, and not all
of them. We might not have processed the SIGCHLD even of a
previous invocation and we don't want to maintain a
unbounded *per-child* event queue, hence we really don't
want anything flushed out of the kernel's queue that we
don't care about. Since this is O(n) this means that if you
have a lot of processes you probably want to handle SIGCHLD
yourself.
We do not reap the children here (by using WNOWAIT), this
is only done after the event source is dispatched so that
the callback still sees the process as a zombie.
*/
/* So, this is ugly. We iteratively invoke waitid() with P_PID + WNOHANG for each PID we wait
* for, instead of using P_ALL. This is because we only want to get child information of very
* specific child processes, and not all of them. We might not have processed the SIGCHLD event
* of a previous invocation and we don't want to maintain a unbounded *per-child* event queue,
* hence we really don't want anything flushed out of the kernel's queue that we don't care
* about. Since this is O(n) this means that if you have a lot of processes you probably want
* to handle SIGCHLD yourself.
*
* We do not reap the children here (by using WNOWAIT), this is only done after the event
* source is dispatched so that the callback still sees the process as a zombie. */
HASHMAP_FOREACH(s, e->child_sources) {
assert(s->type == SOURCE_CHILD);
@ -3251,7 +3244,9 @@ static int process_child(sd_event *e, int64_t threshold, int64_t *ret_min_priori
if (s->child.exited)
continue;
if (EVENT_SOURCE_WATCH_PIDFD(s)) /* There's a usable pidfd known for this event source? then don't waitid() for it here */
if (EVENT_SOURCE_WATCH_PIDFD(s))
/* There's a usable pidfd known for this event source? Then don't waitid() for
* it here */
continue;
zero(s->child.siginfo);
@ -3266,10 +3261,9 @@ static int process_child(sd_event *e, int64_t threshold, int64_t *ret_min_priori
s->child.exited = true;
if (!zombie && (s->child.options & WEXITED)) {
/* If the child isn't dead then let's
* immediately remove the state change
* from the queue, since there's no
* benefit in leaving it queued */
/* If the child isn't dead then let's immediately remove the state
* change from the queue, since there's no benefit in leaving it
* queued. */
assert(s->child.options & (WSTOPPED|WCONTINUED));
(void) waitid(P_PID, s->child.pid, &s->child.siginfo, WNOHANG|(s->child.options & (WSTOPPED|WCONTINUED)));
@ -3324,19 +3318,16 @@ static int process_signal(sd_event *e, struct signal_data *d, uint32_t events, i
assert_return(events == EPOLLIN, -EIO);
assert(min_priority);
/* If there's a signal queued on this priority and SIGCHLD is
on this priority too, then make sure to recheck the
children we watch. This is because we only ever dequeue
the first signal per priority, and if we dequeue one, and
SIGCHLD might be enqueued later we wouldn't know, but we
might have higher priority children we care about hence we
need to check that explicitly. */
/* If there's a signal queued on this priority and SIGCHLD is on this priority too, then make
* sure to recheck the children we watch. This is because we only ever dequeue the first signal
* per priority, and if we dequeue one, and SIGCHLD might be enqueued later we wouldn't know,
* but we might have higher priority children we care about hence we need to check that
* explicitly. */
if (sigismember(&d->sigset, SIGCHLD))
e->need_process_child = true;
/* If there's already an event source pending for this
* priority we don't read another */
/* If there's already an event source pending for this priority we don't read another */
if (d->current)
return 0;