X-Git-Url: https://git.lttng.org/?p=lttng-tools.git;a=blobdiff_plain;f=src%2Fcommon%2Fcompat%2Fcompat-poll.c;h=0c59e98ce9917c4b22b5912d1e88e23fe4c777ae;hp=2318920aed84a7c9dcdb5c1668035913ecb0ff10;hb=4fb28dfc10106c4095ca3b1155d4da9a04467fd1;hpb=a1de8fcc86468f9ae88786634face3e327e2f3b3

diff --git a/src/common/compat/compat-poll.c b/src/common/compat/compat-poll.c
index 2318920ae..0c59e98ce 100644
--- a/src/common/compat/compat-poll.c
+++ b/src/common/compat/compat-poll.c
@@ -1,19 +1,9 @@
 /*
- * Copyright (C)  2011 - David Goulet <david.goulet@polymtl.ca>
- * Copyright (C)  2019 - Yannick Lamarre <ylamarre@efficios.com>
+ * Copyright (C) 2011 David Goulet <david.goulet@polymtl.ca>
+ * Copyright (C) 2019 Yannick Lamarre <ylamarre@efficios.com>
  *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License, version 2 only,
- * as published by the Free Software Foundation.
+ * SPDX-License-Identifier: GPL-2.0-only
  *
- * This program is distributed in the hope that it will be useful, but WITHOUT
- * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
- * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
- * more details.
- *
- * You should have received a copy of the GNU General Public License along
- * with this program; if not, write to the Free Software Foundation, Inc.,
- * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
 #define _LGPL_SOURCE
@@ -30,7 +20,14 @@
 
 #include "poll.h"
 
-unsigned int poll_max_size;
+
+/*
+ * Maximum number of fd we can monitor.
+ *
+ * For poll(2), the max fds must not exceed RLIMIT_NOFILE given by
+ * getrlimit(2).
+ */
+static unsigned int poll_max_size;
 
 /*
  * Resize the epoll events structure of the new size.
@@ -103,6 +100,7 @@ error:
 /*
  * Create pollfd data structure.
  */
+LTTNG_HIDDEN
 int compat_poll_create(struct lttng_poll_event *events, int size)
 {
 	struct compat_poll_event_array *current, *wait;
@@ -155,6 +153,7 @@ error:
 /*
  * Add fd to pollfd data structure with requested events.
  */
+LTTNG_HIDDEN
 int compat_poll_add(struct lttng_poll_event *events, int fd,
 		uint32_t req_events)
 {
@@ -201,6 +200,7 @@ error:
 /*
  * Modify an fd's events..
  */
+LTTNG_HIDDEN
 int compat_poll_mod(struct lttng_poll_event *events, int fd,
 		uint32_t req_events)
 {
@@ -237,6 +237,7 @@ error:
 /*
  * Remove a fd from the pollfd structure.
  */
+LTTNG_HIDDEN
 int compat_poll_del(struct lttng_poll_event *events, int fd)
 {
 	int i, count = 0, ret;
@@ -291,15 +292,18 @@ error:
 /*
  * Wait on poll() with timeout. Blocking call.
  */
-int compat_poll_wait(struct lttng_poll_event *events, int timeout)
+LTTNG_HIDDEN
+int compat_poll_wait(struct lttng_poll_event *events, int timeout,
+		bool interruptible)
 {
-	int ret;
+	int ret, active_fd_count;
+	int idle_pfd_index = 0;
+	size_t i;
 
 	if (events == NULL || events->current.events == NULL) {
 		ERR("poll wait arguments error");
 		goto error;
 	}
-	assert(events->current.nb_fd >= 0);
 
 	if (events->current.nb_fd == 0) {
 		/* Return an invalid error to be consistent with epoll. */
@@ -318,18 +322,47 @@ int compat_poll_wait(struct lttng_poll_event *events, int timeout)
 
 	do {
 		ret = poll(events->wait.events, events->wait.nb_fd, timeout);
-	} while (ret == -1 && errno == EINTR);
+	} while (!interruptible && ret == -1 && errno == EINTR);
 	if (ret < 0) {
-		/* At this point, every error is fatal */
-		PERROR("poll wait");
+		if (errno != EINTR) {
+			PERROR("poll wait");
+		}
 		goto error;
 	}
 
+	active_fd_count = ret;
+
 	/*
-	 * poll() should always iterate on all FDs since we handle the pollset in
-	 * user space and after poll returns, we have to try every fd for a match.
+	 * Swap all active pollfd structs to the beginning of the
+	 * array to emulate compat-epoll behaviour. This algorithm takes
+	 * advantage of poll's returned value and the burst nature of active
+	 * events on the file descriptors. The while loop guarantees that
+	 * idle_pfd will always point to an idle fd.
 	 */
-	return events->wait.nb_fd;
+	if (active_fd_count == events->wait.nb_fd) {
+		goto end;
+	}
+	while (idle_pfd_index < active_fd_count &&
+			events->wait.events[idle_pfd_index].revents != 0) {
+		idle_pfd_index++;
+	}
+
+	for (i = idle_pfd_index + 1; idle_pfd_index < active_fd_count;
+			i++) {
+		struct pollfd swap_pfd;
+		struct pollfd *idle_pfd = &events->wait.events[idle_pfd_index];
+		struct pollfd *current_pfd = &events->wait.events[i];
+
+		if (idle_pfd->revents != 0) {
+			swap_pfd = *current_pfd;
+			*current_pfd = *idle_pfd;
+			*idle_pfd = swap_pfd;
+			idle_pfd_index++;
+		}
+	}
+
+end:
+	return ret;
 
 error:
 	return -1;
@@ -338,6 +371,7 @@ error:
 /*
  * Setup poll set maximum size.
  */
+LTTNG_HIDDEN
 int compat_poll_set_max_size(void)
 {
 	int ret, retval = 0;