Add poll/epoll compat layer for session daemon

[lttng-tools.git] / ltt-sessiond / compat / compat-epoll.c

diff --git a/ltt-sessiond/compat/compat-epoll.c b/ltt-sessiond/compat/compat-epoll.c
new file mode 100644 (file)
index 0000000..578dd2e
--- /dev/null
+++ b/ltt-sessiond/compat/compat-epoll.c
@@ -0,0 +1,218 @@
+/*
+ * Copyright (C)  2011 - David Goulet <david.goulet@polymtl.ca>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; only version 2 of the License.
+ *
+ * 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., 59 Temple
+ * Place - Suite 330, Boston, MA  02111-1307, USA.
+ */
+
+#include <fcntl.h>
+#include <limits.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+#include <lttngerr.h>
+
+#include "poll.h"
+
+unsigned int poll_max_size;
+
+/*
+ * Create epoll set and allocate returned events structure.
+ */
+int compat_epoll_create(struct lttng_poll_event *events, int size, int flags)
+{
+       int ret;
+
+       if (events == NULL || size <= 0) {
+               goto error;
+       }
+
+       /* Don't bust the limit here */
+       if (size > poll_max_size) {
+               size = poll_max_size;
+       }
+
+       ret = epoll_create1(flags);
+       if (ret < 0) {
+               /* At this point, every error is fatal */
+               perror("epoll_create1");
+               goto error;
+       }
+
+       events->epfd = ret;
+
+       /* This *must* be freed by using lttng_poll_free() */
+       events->events = zmalloc(size * sizeof(struct epoll_event));
+       if (events->events == NULL) {
+               perror("malloc epoll set");
+               goto error_close;
+       }
+
+       events->events_size = size;
+       events->nb_fd = 0;
+
+       return 0;
+
+error_close:
+       close(events->epfd);
+error:
+       return -1;
+}
+
+/*
+ * Add a fd to the epoll set with requesting events.
+ */
+int compat_epoll_add(struct lttng_poll_event *events, int fd, uint32_t req_events)
+{
+       int ret, new_size;
+       struct epoll_event ev, *ptr;
+
+       if (events == NULL || events->events == NULL || fd < 0) {
+               ERR("Bad compat epoll add arguments");
+               goto error;
+       }
+
+       ev.events = req_events;
+       ev.data.fd = fd;
+
+       ret = epoll_ctl(events->epfd, EPOLL_CTL_ADD, fd, &ev);
+       if (ret < 0) {
+               switch (errno) {
+               case EEXIST:
+               case ENOSPC:
+               case EPERM:
+                       /* Print perror and goto end not failing. Show must go on. */
+                       perror("epoll_ctl ADD");
+                       goto end;
+               default:
+                       perror("epoll_ctl ADD fatal");
+                       goto error;
+               }
+       }
+
+       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;
+
+error:
+       return -1;
+}
+
+/*
+ * Remove a fd from the epoll set.
+ */
+int compat_epoll_del(struct lttng_poll_event *events, int fd)
+{
+       int ret;
+
+       if (events == NULL || fd < 0) {
+               goto error;
+       }
+
+       ret = epoll_ctl(events->epfd, EPOLL_CTL_DEL, fd, NULL);
+       if (ret < 0) {
+               switch (errno) {
+               case ENOENT:
+               case EPERM:
+                       /* Print perror and goto end not failing. Show must go on. */
+                       perror("epoll_ctl DEL");
+                       goto end;
+               default:
+                       perror("epoll_ctl DEL fatal");
+                       goto error;
+               }
+               perror("epoll_ctl del");
+               goto error;
+       }
+
+       events->nb_fd--;
+
+end:
+       return 0;
+
+error:
+       return -1;
+}
+
+/*
+ * Wait on epoll set. This is a blocking call of timeout value.
+ */
+int compat_epoll_wait(struct lttng_poll_event *events, int timeout)
+{
+       int ret;
+
+       if (events == NULL || events->events == NULL ||
+                       events->events_size < events->nb_fd) {
+               ERR("Wrong arguments in compat_epoll_wait");
+               goto error;
+       }
+
+       ret = epoll_wait(events->epfd, events->events, events->nb_fd, timeout);
+       if (ret < 0) {
+               /* At this point, every error is fatal */
+               perror("epoll_wait");
+               goto error;
+       }
+
+       return ret;
+
+error:
+       return -1;
+}
+
+/*
+ * Setup poll set maximum size.
+ */
+void compat_epoll_set_max_size(void)
+{
+       int ret, fd;
+       char buf[64];
+
+       poll_max_size = LTTNG_POLL_DEFAULT_SIZE;
+
+       fd = open(LTTNG_EPOLL_PROC_PATH, O_RDONLY);
+       if (fd < 0) {
+               return;
+       }
+
+       ret = read(fd, buf, sizeof(buf));
+       if (ret < 0) {
+               perror("read set max size");
+               goto error;
+       }
+
+       poll_max_size = atoi(buf);
+       if (poll_max_size <= 0) {
+               /* Extra precaution */
+               poll_max_size = LTTNG_POLL_DEFAULT_SIZE;
+       }
+
+       DBG("epoll set max size is %d", poll_max_size);
+
+error:
+       close(fd);
+}