compat: remove always true assertion in compat-poll.c

[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 2318920aed84a7c9dcdb5c1668035913ecb0ff10..1193b785f9874e8bcd15cd16b72673b3f0d7f645 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;
@@ -291,15 +302,18 @@ 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 +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;
+
        /*
-        * 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 +381,7 @@ error:
 /*
  * Setup poll set maximum size.
  */
+LTTNG_HIDDEN
 int compat_poll_set_max_size(void)
 {
        int ret, retval = 0;