Fix: common: poll: compat_poll_wait never finishes

[lttng-tools.git] / src / common / compat / compat-poll.c

diff --git a/src/common/compat/compat-poll.c b/src/common/compat/compat-poll.c
index 0220b27854ab776294404c6c80e9a5608bfdeb54..499a2762307f61c16023d574fba7aa337c10c6f9 100644 (file)
--- a/src/common/compat/compat-poll.c
+++ b/src/common/compat/compat-poll.c
@@ -30,7 +30,14 @@
 
 #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 +110,7 @@ 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 +163,7 @@ 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 +210,7 @@ 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 +247,7 @@ 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;
@@ -291,11 +302,12 @@ 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, active_fd_count;
-       int idle_pfd_index = 0;
-       size_t i;
+       size_t pos = 0, consecutive_entries = 0, non_idle_pos;
 
        if (events == NULL || events->current.events == NULL) {
                ERR("poll wait arguments error");
@@ -320,44 +332,47 @@ 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;
 
        /*
-        * 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.
+        * Move all active pollfd structs to the beginning of the
+        * array to emulate compat-epoll behaviour.
         */
        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 (ipfd->revents != 0) {
-                       swap_pfd = *current_pfd;
-                       *current_pfd = *idle_pfd;
-                       *idle_pfd = swap_pfd;
-                       idle_pfd_index++;
+       while (consecutive_entries != active_fd_count) {
+               struct pollfd *current = &events->wait.events[pos];
+               struct pollfd idle_entry;
+
+               if (current->revents != 0) {
+                       consecutive_entries++;
+                       pos++;
+                       continue;
                }
-       }
 
+               non_idle_pos = pos;
+
+               /* Look for next non-idle entry. */
+               while (events->wait.events[++non_idle_pos].revents == 0);
+
+               /* Swap idle and non-idle entries. */
+               idle_entry = *current;
+               *current = events->wait.events[non_idle_pos];
+               events->wait.events[non_idle_pos] = idle_entry;
+
+               consecutive_entries++;
+               pos++;
+       }
 end:
        return ret;
 
@@ -368,6 +383,7 @@ error:
 /*
  * Setup poll set maximum size.
  */
+LTTNG_HIDDEN
 int compat_poll_set_max_size(void)
 {
        int ret, retval = 0;