[make-initrd] [PATCH] ueventd: Don't use a epoll timeout when it's not needed

[Alexey Gladkov]

The timeout is used to process queues that have unprocessed events
(dirty ones) even when no new events have arrived in the queue. When
there are no dirty queues, then there is no point in extra iterations of
the main loop.

Signed-off-by: Alexey Gladkov <gladkov.alexey at gmail.com>
---
 datasrc/ueventd/ueventd.c | 23 ++++++++++++++++++-----
 1 file changed, 18 insertions(+), 5 deletions(-)

diff --git a/datasrc/ueventd/ueventd.c b/datasrc/ueventd/ueventd.c
index 857d3b4f..afe050d0 100644
--- a/datasrc/ueventd/ueventd.c
+++ b/datasrc/ueventd/ueventd.c
@@ -56,7 +56,8 @@ enum {
 	PIPE_MAX,
 };
 
-int pipefd[PIPE_MAX];
+static int pipefd[PIPE_MAX];
+static int dirty_queues = 0;
 
 #define EV_PAUSE_MASK (IN_CREATE | IN_DELETE | IN_ONLYDIR)
 #define EV_ROOT_MASK  (IN_CREATE | IN_ONLYDIR)
@@ -121,8 +122,10 @@ int watch_path(int inotifyfd, const char *dir, const char *name, uint32_t mask,
 	new->next      = watch_list;
 
 	if (flags & F_QUEUE_DIR) {
-		if (!empty_directory(path))
+		if (!empty_directory(path)) {
 			new->q_flags |= F_DIRTY;
+			dirty_queues++;
+		}
 		new->q_parentfd = pipefd[PIPE_WRITE];
 	}
 
@@ -339,8 +342,10 @@ int process_inotify_events(int inotifyfd)
 				continue;
 			}
 
-			if (!(p->q_flags & F_DIRTY))
+			if (!(p->q_flags & F_DIRTY)) {
 				p->q_flags |= F_DIRTY;
+				dirty_queues++;
+			}
 		}
 	}
 	return 0;
@@ -375,8 +380,10 @@ int process_pipefd_events(int readfd)
 		for (p = watch_list; p; p = p->next) {
 			if (!(p->q_flags & F_QUEUE_DIR) || p->q_watchfd != value)
 				continue;
-			if (!(p->q_flags & F_DIRTY))
+			if (!(p->q_flags & F_DIRTY)) {
 				p->q_flags |= F_DIRTY;
+				dirty_queues++;
+			}
 			break;
 		}
 	}
@@ -521,7 +528,7 @@ int main(int argc, char **argv)
 		int fdcount;
 
 		errno = 0;
-		fdcount = epoll_wait(epollfd, ev, EV_MAX, 250);
+		fdcount = epoll_wait(epollfd, ev, EV_MAX, (dirty_queues ? 250 : -1));
 
 		if (fdcount < 0) {
 			if (errno == EINTR)
@@ -542,6 +549,12 @@ int main(int argc, char **argv)
 		for (e = watch_list; e; e = e->next) {
 			if (!(e->q_flags & F_QUEUE_DIR) || !(e->q_flags & F_DIRTY) || (e->q_pid != 0) || (e->q_flags & F_PAUSED))
 				continue;
+
+			if (dirty_queues == 0)
+				rd_fatal("BUG: dirty_queues == 0, but dirty queues are present");
+
+			dirty_queues--;
+
 			e->q_flags &= ~F_DIRTY;
 			e->q_pid = spawn_worker(epollfd, e);
 		}
-- 
2.33.8