X-Git-Url: https://git.lttng.org/?p=lttng-tools.git;a=blobdiff_plain;f=src%2Fcommon%2Fcompat%2Fcompat-epoll.c;h=40451b3d21286106430c1322209b21d9fef9579f;hp=e1672c4c3178afbbce32acddebf2b30cea66fe09;hb=d21b0d71990ac6ec4272c1f80f0ca544103628b3;hpb=c617c0c651432f9d5ae7adf4c5c1a5fd92ad828e

diff --git a/src/common/compat/compat-epoll.c b/src/common/compat/compat-epoll.c
index e1672c4c3..40451b3d2 100644
--- a/src/common/compat/compat-epoll.c
+++ b/src/common/compat/compat-epoll.c
@@ -16,6 +16,7 @@
  */
 
 #define _GNU_SOURCE
+#include <assert.h>
 #include <fcntl.h>
 #include <limits.h>
 #include <stdlib.h>
@@ -31,6 +32,32 @@
 
 unsigned int poll_max_size;
 
+/*
+ * Resize the epoll events structure of the new size.
+ *
+ * Return 0 on success or else -1 with the current events pointer untouched.
+ */
+static int resize_poll_event(struct lttng_poll_event *events,
+		uint32_t new_size)
+{
+	struct epoll_event *ptr;
+
+	assert(events);
+
+	ptr = realloc(events->events, new_size * sizeof(*ptr));
+	if (ptr == NULL) {
+		PERROR("realloc epoll add");
+		goto error;
+	}
+	events->events = ptr;
+	events->alloc_size = new_size;
+
+	return 0;
+
+error:
+	return -1;
+}
+
 /*
  * Create epoll set and allocate returned events structure.
  */
@@ -63,7 +90,7 @@ int compat_epoll_create(struct lttng_poll_event *events, int size, int flags)
 		goto error_close;
 	}
 
-	events->events_size = size;
+	events->alloc_size = events->init_size = size;
 	events->nb_fd = 0;
 
 	return 0;
@@ -82,8 +109,8 @@ error:
  */
 int compat_epoll_add(struct lttng_poll_event *events, int fd, uint32_t req_events)
 {
-	int ret, new_size;
-	struct epoll_event ev, *ptr;
+	int ret;
+	struct epoll_event ev;
 
 	if (events == NULL || events->events == NULL || fd < 0) {
 		ERR("Bad compat epoll add arguments");
@@ -112,17 +139,6 @@ int compat_epoll_add(struct lttng_poll_event *events, int fd, uint32_t req_event
 
 	events->nb_fd++;
 
-	if (events->nb_fd >= events->events_size) {
-		new_size = 2 * events->events_size;
-		ptr = realloc(events->events, new_size * sizeof(struct epoll_event));
-		if (ptr == NULL) {
-			PERROR("realloc epoll add");
-			goto error;
-		}
-		events->events = ptr;
-		events->events_size = new_size;
-	}
-
 end:
 	return 0;
 
@@ -172,13 +188,39 @@ error:
 int compat_epoll_wait(struct lttng_poll_event *events, int timeout)
 {
 	int ret;
+	uint32_t new_size;
 
-	if (events == NULL || events->events == NULL ||
-			events->events_size < events->nb_fd) {
+	if (events == NULL || events->events == NULL) {
 		ERR("Wrong arguments in compat_epoll_wait");
 		goto error;
 	}
 
+	/*
+	 * Resize if needed before waiting. We could either expand the array or
+	 * shrink it down. It's important to note that after this step, we are
+	 * ensured that the events argument of the epoll_wait call will be large
+	 * enough to hold every possible returned events.
+	 */
+	if (events->nb_fd > events->alloc_size) {
+		/* Expand if the nb_fd is higher than the actual size. */
+		new_size = events->alloc_size << 1UL;
+	} else if ((events->nb_fd << 1UL) <= events->alloc_size &&
+			events->nb_fd >= events->init_size) {
+		/* Shrink if nb_fd multiplied by two is <= than the actual size. */
+		new_size = events->alloc_size >> 1UL;
+	} else {
+		/* Indicate that we don't want to resize. */
+		new_size = 0;
+	}
+
+	if (new_size) {
+		ret = resize_poll_event(events, new_size);
+		if (ret < 0) {
+			/* ENOMEM problem at this point. */
+			goto error;
+		}
+	}
+
 	do {
 		ret = epoll_wait(events->epfd, events->events, events->nb_fd, timeout);
 	} while (ret == -1 && errno == EINTR);
@@ -220,7 +262,7 @@ void compat_epoll_set_max_size(void)
 	}
 
 	poll_max_size = atoi(buf);
-	if (poll_max_size <= 0) {
+	if (poll_max_size == 0) {
 		/* Extra precaution */
 		poll_max_size = DEFAULT_POLL_SIZE;
 	}