]> sigrok.org Git - libsigrok.git/blobdiff - src/session.c
session: Port to GLib main loop
[libsigrok.git] / src / session.c
index 58be444605e985109ec385c76a33be08eb0fb6a3..cc5f09dccb607910d3cb4ef62789203114bf6aaf 100644 (file)
@@ -2,6 +2,7 @@
  * This file is part of the libsigrok project.
  *
  * Copyright (C) 2010-2012 Bert Vermeulen <bert@biot.com>
+ * Copyright (C) 2015 Daniel Elstner <daniel.kitta@gmail.com>
  *
  * 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
  * @{
  */
 
-struct source {
-       int64_t timeout;        /* microseconds */
-       int64_t due;            /* microseconds */
-
-       sr_receive_data_callback cb;
+struct datafeed_callback {
+       sr_datafeed_callback cb;
        void *cb_data;
+};
 
-       /* This is used to keep track of the object (fd, pollfd or channel) which is
-        * being polled and will be used to match the source when removing it again.
-        */
-       gintptr poll_object;
+/** Custom GLib event source for generic descriptor I/O.
+ * @internal
+ */
+struct fd_source {
+       GSource base;
 
-       /* Number of fds to poll for this source. This will be 0 for timer
-        * sources, 1 for normal I/O sources, and 1 or more for libusb I/O
-        * sources on Unix platforms.
-        */
-       int num_fds;
+       int64_t timeout_us;
+       int64_t due_us;
 
-       gboolean triggered;
-};
+       /* Meta-data needed to keep track of installed sources */
+       struct sr_session *session;
+       void *key;
 
-struct datafeed_callback {
-       sr_datafeed_callback cb;
-       void *cb_data;
+       GPollFD pollfd;
 };
 
+/** FD event source prepare() method.
+ */
+static gboolean fd_source_prepare(GSource *source, int *timeout)
+{
+       int64_t now_us;
+       struct fd_source *fsource;
+       int remaining_ms;
+
+       fsource = (struct fd_source *)source;
+
+       if (fsource->timeout_us >= 0) {
+               now_us = g_source_get_time(source);
+
+               if (fsource->due_us == 0) {
+                       /* First-time initialization of the expiration time */
+                       fsource->due_us = now_us + fsource->timeout_us;
+               }
+               remaining_ms = (MAX(0, fsource->due_us - now_us) + 999) / 1000;
+       } else {
+               remaining_ms = -1;
+       }
+       *timeout = remaining_ms;
+
+       return (remaining_ms == 0);
+}
+
+/** FD event source check() method.
+ */
+static gboolean fd_source_check(GSource *source)
+{
+       struct fd_source *fsource;
+       unsigned int revents;
+
+       fsource = (struct fd_source *)source;
+       revents = fsource->pollfd.revents;
+
+       return (revents != 0 || (fsource->timeout_us >= 0
+                       && fsource->due_us <= g_source_get_time(source)));
+}
+
+/** FD event source dispatch() method.
+ */
+static gboolean fd_source_dispatch(GSource *source,
+               GSourceFunc callback, void *user_data)
+{
+       struct fd_source *fsource;
+       const char *name;
+       unsigned int revents;
+       gboolean keep;
+
+       fsource = (struct fd_source *)source;
+       name = g_source_get_name(source);
+       revents = fsource->pollfd.revents;
+
+       if (revents != 0) {
+               sr_spew("%s: %s " G_POLLFD_FORMAT ", revents 0x%.2X",
+                       __func__, name, fsource->pollfd.fd, revents);
+       } else {
+               sr_spew("%s: %s " G_POLLFD_FORMAT ", timed out",
+                       __func__, name, fsource->pollfd.fd);
+       }
+       if (!callback) {
+               sr_err("Callback not set, cannot dispatch event.");
+               return G_SOURCE_REMOVE;
+       }
+       keep = (*(sr_receive_data_callback)callback)
+                       (fsource->pollfd.fd, revents, user_data);
+
+       if (fsource->timeout_us >= 0 && G_LIKELY(keep)
+                       && G_LIKELY(!g_source_is_destroyed(source)))
+               fsource->due_us = g_source_get_time(source)
+                               + fsource->timeout_us;
+       return keep;
+}
+
+/** FD event source finalize() method.
+ */
+static void fd_source_finalize(GSource *source)
+{
+       struct fd_source *fsource;
+
+       fsource = (struct fd_source *)source;
+
+       sr_dbg("%s: key %p", __func__, fsource->key);
+
+       sr_session_source_destroyed(fsource->session, fsource->key, source);
+}
+
+/** Create an event source for I/O on a file descriptor.
+ *
+ * In order to maintain API compatibility, this event source also doubles
+ * as a timer event source.
+ *
+ * @param session The session the event source belongs to.
+ * @param key The key used to identify this source.
+ * @param fd The file descriptor or HANDLE.
+ * @param timeout_ms The timeout interval in ms, or -1 to wait indefinitely.
+ * @return A new event source object, or NULL on failure.
+ */
+static GSource *fd_source_new(struct sr_session *session, void *key,
+               gintptr fd, int events, int timeout_ms)
+{
+       static GSourceFuncs fd_source_funcs = {
+               .prepare  = &fd_source_prepare,
+               .check    = &fd_source_check,
+               .dispatch = &fd_source_dispatch,
+               .finalize = &fd_source_finalize
+       };
+       GSource *source;
+       struct fd_source *fsource;
+
+       source = g_source_new(&fd_source_funcs, sizeof(struct fd_source));
+       fsource = (struct fd_source *)source;
+
+       g_source_set_name(source, (fd < 0) ? "timer" : "fd");
+
+       if (timeout_ms >= 0) {
+               fsource->timeout_us = 1000 * (int64_t)timeout_ms;
+               fsource->due_us = 0;
+       } else {
+               fsource->timeout_us = -1;
+               fsource->due_us = INT64_MAX;
+       }
+       fsource->session = session;
+       fsource->key = key;
+
+       fsource->pollfd.fd = fd;
+       fsource->pollfd.events = events;
+       fsource->pollfd.revents = 0;
+
+       if (fd >= 0)
+               g_source_add_poll(source, &fsource->pollfd);
+
+       return source;
+}
+
 /**
  * Create a new session.
  *
@@ -95,10 +227,12 @@ SR_API int sr_session_new(struct sr_context *ctx,
 
        session->ctx = ctx;
 
-       session->sources = g_array_new(FALSE, FALSE, sizeof(struct source));
-       session->pollfds = g_array_new(FALSE, FALSE, sizeof(GPollFD));
+       g_mutex_init(&session->main_mutex);
 
-       g_mutex_init(&session->stop_mutex);
+       /* To maintain API compatibility, we need a lookup table
+        * which maps poll_object IDs to GSource* pointers.
+        */
+       session->event_sources = g_hash_table_new(NULL, NULL);
 
        *new_session = session;
 
@@ -124,12 +258,11 @@ SR_API int sr_session_destroy(struct sr_session *session)
        }
 
        sr_session_dev_remove_all(session);
-       g_mutex_clear(&session->stop_mutex);
-
        g_slist_free_full(session->owned_devs, (GDestroyNotify)sr_dev_inst_free);
 
-       g_array_unref(session->pollfds);
-       g_array_unref(session->sources);
+       g_hash_table_unref(session->event_sources);
+
+       g_mutex_clear(&session->main_mutex);
 
        g_free(session);
 
@@ -371,192 +504,6 @@ SR_API int sr_session_trigger_set(struct sr_session *session, struct sr_trigger
        return SR_OK;
 }
 
-static gboolean sr_session_check_aborted(struct sr_session *session)
-{
-       gboolean stop;
-
-       g_mutex_lock(&session->stop_mutex);
-       stop = session->abort_session;
-       if (stop) {
-               sr_session_stop_sync(session);
-               /* But once is enough. */
-               session->abort_session = FALSE;
-       }
-       g_mutex_unlock(&session->stop_mutex);
-
-       return stop;
-}
-
-/**
- * Poll the session's event sources.
- *
- * @param session The session to use. Must not be NULL.
- * @retval SR_OK Success.
- * @retval SR_ERR Error occurred.
- */
-static int sr_session_iteration(struct sr_session *session)
-{
-       int64_t start_time, stop_time, min_due, due;
-       int timeout_ms;
-       unsigned int i;
-       int k, fd_index;
-       int ret;
-       int fd;
-       int revents;
-       gboolean triggered, stopped;
-       struct source *source;
-       GPollFD *pollfd;
-       gintptr poll_object;
-#if HAVE_LIBUSB_1_0
-       int64_t usb_timeout;
-       int64_t usb_due;
-       struct timeval tv;
-#endif
-       if (session->sources->len == 0) {
-               sr_session_check_aborted(session);
-               return SR_OK;
-       }
-       start_time = g_get_monotonic_time();
-       min_due = INT64_MAX;
-
-       for (i = 0; i < session->sources->len; ++i) {
-               source = &g_array_index(session->sources, struct source, i);
-               if (source->due < min_due)
-                       min_due = source->due;
-               source->triggered = FALSE;
-       }
-#if HAVE_LIBUSB_1_0
-       usb_due = INT64_MAX;
-       if (session->ctx->usb_source_present) {
-               ret = libusb_get_next_timeout(session->ctx->libusb_ctx, &tv);
-               if (ret < 0) {
-                       sr_err("Error getting libusb timeout: %s",
-                               libusb_error_name(ret));
-                       return SR_ERR;
-               } else if (ret == 1) {
-                       usb_timeout = (int64_t)tv.tv_sec * G_USEC_PER_SEC
-                                       + tv.tv_usec;
-                       usb_due = start_time + usb_timeout;
-                       if (usb_due < min_due)
-                               min_due = usb_due;
-
-                       sr_spew("poll: next USB timeout %g ms",
-                               1e-3 * usb_timeout);
-               }
-       }
-#endif
-       if (min_due == INT64_MAX)
-               timeout_ms = -1;
-       else if (min_due > start_time)
-               timeout_ms = MIN((min_due - start_time + 999) / 1000, INT_MAX);
-       else
-               timeout_ms = 0;
-
-       sr_spew("poll enter: %u sources, %u fds, %d ms timeout",
-               session->sources->len, session->pollfds->len, timeout_ms);
-
-       ret = g_poll((GPollFD *)session->pollfds->data,
-                       session->pollfds->len, timeout_ms);
-#ifdef G_OS_UNIX
-       if (ret < 0 && errno != EINTR) {
-               sr_err("Error in poll: %s", g_strerror(errno));
-               return SR_ERR;
-       }
-#else
-       if (ret < 0) {
-               sr_err("Error in poll: %d", ret);
-               return SR_ERR;
-       }
-#endif
-       stop_time = g_get_monotonic_time();
-
-       sr_spew("poll leave: %g ms elapsed, %d events",
-               1e-3 * (stop_time - start_time), ret);
-
-       triggered = FALSE;
-       stopped = FALSE;
-       fd_index = 0;
-
-       for (i = 0; i < session->sources->len; ++i) {
-               source = &g_array_index(session->sources, struct source, i);
-
-               poll_object = source->poll_object;
-               fd = (int)poll_object;
-               revents = 0;
-
-               for (k = 0; k < source->num_fds; ++k) {
-                       pollfd = &g_array_index(session->pollfds,
-                                       GPollFD, fd_index + k);
-                       fd = pollfd->fd;
-                       revents |= pollfd->revents;
-               }
-               fd_index += source->num_fds;
-
-               if (source->triggered)
-                       continue; /* already handled */
-               if (ret > 0 && revents == 0)
-                       continue; /* skip timeouts if any I/O event occurred */
-
-               /* Make invalid to avoid confusion in case of multiple FDs. */
-               if (source->num_fds > 1)
-                       fd = -1;
-               if (ret <= 0)
-                       revents = 0;
-
-               due = source->due;
-#if HAVE_LIBUSB_1_0
-               if (usb_due < due && poll_object
-                               == (gintptr)session->ctx->libusb_ctx)
-                       due = usb_due;
-#endif
-               if (revents == 0 && stop_time < due)
-                       continue;
-               /*
-                * The source may be gone after the callback returns,
-                * so access any data now that needs accessing.
-                */
-               if (source->timeout >= 0)
-                       source->due = stop_time + source->timeout;
-               source->triggered = TRUE;
-               triggered = TRUE;
-               /*
-                * Invoke the source's callback on an event or timeout.
-                */
-               sr_spew("callback for event source %" G_GINTPTR_FORMAT " with"
-                       " event mask 0x%.2X", poll_object, (unsigned)revents);
-               if (!source->cb(fd, revents, source->cb_data)) {
-#if HAVE_LIBUSB_1_0
-                       /* Hackish, to be cleaned up when porting to
-                        * the GLib main loop.
-                        */
-                       if (poll_object == (gintptr)session->ctx->libusb_ctx)
-                               usb_source_remove(session, session->ctx);
-                       else
-#endif
-                               sr_session_source_remove_internal(session,
-                                               poll_object);
-               }
-               /*
-                * We want to take as little time as possible to stop
-                * the session if we have been told to do so. Therefore,
-                * we check the flag after processing every source, not
-                * just once per main event loop.
-                */
-               if (!stopped)
-                       stopped = sr_session_check_aborted(session);
-
-               /* Restart loop as the sources list may have changed. */
-               fd_index = 0;
-               i = 0;
-       }
-
-       /* Check for abort at least once per iteration. */
-       if (!triggered)
-               sr_session_check_aborted(session);
-
-       return SR_OK;
-}
-
 static int verify_trigger(struct sr_trigger *trigger)
 {
        struct sr_trigger_stage *stage;
@@ -593,6 +540,85 @@ static int verify_trigger(struct sr_trigger *trigger)
        return SR_OK;
 }
 
+/** Set up the main context the session will be executing in.
+ *
+ * Must be called just before the session starts, by the thread which
+ * will execute the session main loop. Once acquired, the main context
+ * pointer is immutable for the duration of the session run.
+ */
+static int set_main_context(struct sr_session *session)
+{
+       GMainContext *def_context;
+
+       /* May happen if sr_session_start() is called again after
+        * sr_session_run(), but the session hasn't been stopped yet.
+        */
+       if (session->main_loop) {
+               sr_err("Cannot set main context; main loop already created.");
+               return SR_ERR;
+       }
+
+       g_mutex_lock(&session->main_mutex);
+
+       def_context = g_main_context_get_thread_default();
+
+       if (!def_context)
+               def_context = g_main_context_default();
+       /*
+        * Try to use an existing main context if possible, but only if we
+        * can make it owned by the current thread. Otherwise, create our
+        * own main context so that event source callbacks can execute in
+        * the session thread.
+        */
+       if (g_main_context_acquire(def_context)) {
+               g_main_context_release(def_context);
+
+               sr_dbg("Using thread-default main context.");
+
+               session->main_context = def_context;
+               session->main_context_is_default = TRUE;
+       } else {
+               sr_dbg("Creating our own main context.");
+
+               session->main_context = g_main_context_new();
+               session->main_context_is_default = FALSE;
+       }
+       g_mutex_unlock(&session->main_mutex);
+
+       return SR_OK;
+}
+
+/** Unset the main context used for the current session run.
+ *
+ * Must be called right after stopping the session. Note that if the
+ * session is stopped asynchronously, the main loop may still be running
+ * after the main context has been unset. This is OK as long as no new
+ * event sources are created -- the main loop holds its own reference
+ * to the main context.
+ */
+static int unset_main_context(struct sr_session *session)
+{
+       int ret;
+
+       g_mutex_lock(&session->main_mutex);
+
+       if (session->main_context) {
+               if (!session->main_context_is_default)
+                       g_main_context_unref(session->main_context);
+
+               session->main_context = NULL;
+               ret = SR_OK;
+       } else {
+               /* May happen if the set/unset calls are not matched.
+                */
+               sr_err("No main context to unset.");
+               ret = SR_ERR;
+       }
+       g_mutex_unlock(&session->main_mutex);
+
+       return ret;
+}
+
 /**
  * Start a session.
  *
@@ -624,9 +650,14 @@ SR_API int sr_session_start(struct sr_session *session)
        if (session->trigger && verify_trigger(session->trigger) != SR_OK)
                return SR_ERR;
 
+       ret = set_main_context(session);
+       if (ret != SR_OK)
+               return ret;
+
+       session->running = TRUE;
+
        sr_info("Starting.");
 
-       ret = SR_OK;
        for (l = session->devs; l; l = l->next) {
                sdi = l->data;
                enabled_channels = 0;
@@ -656,6 +687,10 @@ SR_API int sr_session_start(struct sr_session *session)
                }
        }
 
+       if (ret != SR_OK) {
+               unset_main_context(session);
+               session->running = FALSE;
+       }
        /* TODO: What if there are multiple devices? Which return code? */
 
        return ret;
@@ -674,70 +709,65 @@ SR_API int sr_session_start(struct sr_session *session)
  */
 SR_API int sr_session_run(struct sr_session *session)
 {
-       int ret;
-
        if (!session) {
                sr_err("%s: session was NULL", __func__);
                return SR_ERR_ARG;
        }
-
        if (!session->devs) {
                /* TODO: Actually the case? */
                sr_err("%s: session->devs was NULL; a session "
                       "cannot be run without devices.", __func__);
                return SR_ERR_ARG;
        }
-       session->running = TRUE;
+       if (session->main_loop) {
+               sr_err("Main loop already created.");
+               return SR_ERR;
+       }
+       if (g_hash_table_size(session->event_sources) == 0) {
+               sr_err("Refusing to run without any event sources.");
+               return SR_ERR;
+       }
 
+       g_mutex_lock(&session->main_mutex);
+       if (!session->main_context) {
+               sr_err("Cannot run without main context.");
+               g_mutex_unlock(&session->main_mutex);
+               return SR_ERR;
+       }
        sr_info("Running.");
 
-       /* Poll event sources until none are left. */
-       while (session->sources->len > 0) {
-               ret = sr_session_iteration(session);
-               if (ret != SR_OK)
-                       return ret;
-       }
+       session->main_loop = g_main_loop_new(session->main_context, FALSE);
+       g_mutex_unlock(&session->main_mutex);
+
+       g_main_loop_run(session->main_loop);
+
+       g_main_loop_unref(session->main_loop);
+       session->main_loop = NULL;
+
        return SR_OK;
 }
 
-/**
- * Stop a session.
- *
- * The session is stopped immediately, with all acquisition sessions stopped
- * and hardware drivers cleaned up.
- *
- * This must be called from within the session thread, to prevent freeing
- * resources that the session thread will try to use.
- *
- * @param session The session to use. Must not be NULL.
- *
- * @retval SR_OK Success.
- * @retval SR_ERR_ARG Invalid session passed.
- *
- * @private
- */
-SR_PRIV int sr_session_stop_sync(struct sr_session *session)
+static gboolean session_stop_sync(void *user_data)
 {
+       struct sr_session *session;
        struct sr_dev_inst *sdi;
-       GSList *l;
+       GSList *node;
 
-       if (!session) {
-               sr_err("%s: session was NULL", __func__);
-               return SR_ERR_ARG;
-       }
+       session = user_data;
+
+       if (!session->running)
+               return G_SOURCE_REMOVE;
 
        sr_info("Stopping.");
 
-       for (l = session->devs; l; l = l->next) {
-               sdi = l->data;
-               if (sdi->driver) {
-                       if (sdi->driver->dev_acquisition_stop)
-                               sdi->driver->dev_acquisition_stop(sdi, sdi);
-               }
+       for (node = session->devs; node; node = node->next) {
+               sdi = node->data;
+               if (sdi->driver && sdi->driver->dev_acquisition_stop)
+                       sdi->driver->dev_acquisition_stop(sdi, sdi);
        }
        session->running = FALSE;
 
-       return SR_OK;
+       return G_SOURCE_REMOVE;
 }
 
 /**
@@ -755,6 +785,7 @@ SR_PRIV int sr_session_stop_sync(struct sr_session *session)
  *
  * @retval SR_OK Success.
  * @retval SR_ERR_ARG Invalid session passed.
+ * @retval SR_ERR Other error.
  *
  * @since 0.4.0
  */
@@ -762,14 +793,19 @@ SR_API int sr_session_stop(struct sr_session *session)
 {
        if (!session) {
                sr_err("%s: session was NULL", __func__);
-               return SR_ERR_BUG;
+               return SR_ERR_ARG;
        }
+       g_mutex_lock(&session->main_mutex);
 
-       g_mutex_lock(&session->stop_mutex);
-       session->abort_session = TRUE;
-       g_mutex_unlock(&session->stop_mutex);
+       if (session->main_context) {
+               g_main_context_invoke(session->main_context,
+                               &session_stop_sync, session);
+       } else {
+               sr_err("No main context set; already stopped?");
+       }
+       g_mutex_unlock(&session->main_mutex);
 
-       return SR_OK;
+       return unset_main_context(session);
 }
 
 /**
@@ -910,107 +946,62 @@ SR_PRIV int sr_session_send(const struct sr_dev_inst *sdi,
  * Add an event source for a file descriptor.
  *
  * @param session The session to use. Must not be NULL.
- * @param[in] timeout Max time in ms to wait before the callback is called,
- *                    or -1 to wait indefinitely.
- * @param cb Callback function to add. Must not be NULL.
- * @param cb_data Data for the callback function. Can be NULL.
- * @param poll_object Handle by which the source is identified
- *
+ * @param key The key which identifies the event source.
+ * @param source An event source object. Must not be NULL.
  * @retval SR_OK Success.
  * @retval SR_ERR_ARG Invalid argument.
- * @retval SR_ERR An event source for @a poll_object is already installed.
+ * @retval SR_ERR_BUG Event source with @a key already installed.
+ * @retval SR_ERR Other error.
  */
 SR_PRIV int sr_session_source_add_internal(struct sr_session *session,
-               int timeout, sr_receive_data_callback cb, void *cb_data,
-               gintptr poll_object)
+               void *key, GSource *source)
 {
-       struct source src;
-       unsigned int i;
-
-       /* Note: cb_data can be NULL, that's not a bug. */
-       if (!cb) {
-               sr_err("%s: cb was NULL", __func__);
-               return SR_ERR_ARG;
-       }
-       /* Make sure that poll_object is unique.
+       int ret;
+       /*
+        * This must not ever happen, since the source has already been
+        * created and its finalize() method will remove the key for the
+        * already installed source. (Well it would, if we did not have
+        * another sanity check there.)
         */
-       for (i = 0; i < session->sources->len; ++i) {
-               if (g_array_index(session->sources, struct source, i)
-                               .poll_object == poll_object) {
-                       sr_err("Event source %" G_GINTPTR_FORMAT
-                               " already installed.", poll_object);
-                       return SR_ERR;
-               }
+       if (g_hash_table_contains(session->event_sources, key)) {
+               sr_err("Event source with key %p already exists.", key);
+               return SR_ERR_BUG;
        }
-       sr_dbg("Installing event source %" G_GINTPTR_FORMAT
-               " with %d ms timeout.", poll_object, timeout);
-       src.cb = cb;
-       src.cb_data = cb_data;
-       src.poll_object = poll_object;
-       src.num_fds = 0;
-       src.triggered = FALSE;
-
-       if (timeout >= 0) {
-               src.timeout = INT64_C(1000) * timeout;
-               src.due = g_get_monotonic_time() + src.timeout;
+       g_hash_table_insert(session->event_sources, key, source);
+
+       g_mutex_lock(&session->main_mutex);
+
+       if (session->main_context) {
+               if (g_source_attach(source, session->main_context) > 0)
+                       ret = SR_OK;
+               else
+                       ret = SR_ERR;
        } else {
-               src.timeout = -1;
-               src.due = INT64_MAX;
+               sr_err("Cannot add event source without main context.");
+               ret = SR_ERR;
        }
-       g_array_append_val(session->sources, src);
+       g_mutex_unlock(&session->main_mutex);
 
-       return SR_OK;
+       return ret;
 }
 
-SR_PRIV int sr_session_source_poll_add(struct sr_session *session,
-               gintptr poll_object, gintptr fd, int events)
+static int attach_fd_source(struct sr_session *session,
+               void *key, int fd, int events, int timeout,
+               sr_receive_data_callback cb, void *cb_data)
 {
-       struct source *source;
-       GPollFD pollfd;
-       unsigned int i;
-       int fd_index, k;
-
-       source = NULL;
-       fd_index = 0;
+       GSource *source;
+       int ret;
 
-       /* Look up existing event source.
-        */
-       for (i = 0; i < session->sources->len; ++i) {
-               source = &g_array_index(session->sources, struct source, i);
-               if (source->poll_object == poll_object)
-                       break;
-               fd_index += source->num_fds;
-       }
-       if (!source) {
-               sr_err("Cannot add poll FD %" G_GINTPTR_FORMAT
-                       " to non-existing event source %" G_GINTPTR_FORMAT
-                       ".",  fd, poll_object);
+       source = fd_source_new(session, key, fd, events, timeout);
+       if (!source)
                return SR_ERR;
-       }
-       /* Make sure the FD is unique.
-        */
-       for (k = 0; k < source->num_fds; ++k)
-               if (g_array_index(session->pollfds, GPollFD, fd_index + k)
-                               .fd == fd) {
-                       sr_err("Cannot add poll FD %" G_GINTPTR_FORMAT
-                               " twice to event source %" G_GINTPTR_FORMAT
-                               ".", fd, poll_object);
-                       return SR_ERR;
-               }
-
-       pollfd.fd = fd;
-       pollfd.events = events;
-       pollfd.revents = 0;
 
-       g_array_insert_val(session->pollfds,
-               fd_index + source->num_fds, pollfd);
-       ++source->num_fds;
+       g_source_set_callback(source, (GSourceFunc)cb, cb_data, NULL);
 
-       sr_dbg("Added poll FD %" G_GINTPTR_FORMAT " with event mask 0x%.2X"
-               " to event source %" G_GINTPTR_FORMAT ".",
-               fd, (unsigned)events, poll_object);
+       ret = sr_session_source_add_internal(session, key, source);
+       g_source_unref(source);
 
-       return SR_OK;
+       return ret;
 }
 
 /**
@@ -1032,17 +1023,12 @@ SR_PRIV int sr_session_source_poll_add(struct sr_session *session,
 SR_API int sr_session_source_add(struct sr_session *session, int fd,
                int events, int timeout, sr_receive_data_callback cb, void *cb_data)
 {
-       int ret;
-
        if (fd < 0 && timeout < 0) {
-               sr_err("Timer source without timeout would block indefinitely");
+               sr_err("Cannot create timer source without timeout.");
                return SR_ERR_ARG;
        }
-       ret = sr_session_source_add_internal(session, timeout, cb, cb_data, fd);
-       if (ret != SR_OK || fd < 0)
-               return ret;
-
-       return sr_session_source_poll_add(session, fd, fd, events);
+       return attach_fd_source(session, GINT_TO_POINTER(fd),
+                       fd, events, timeout, cb, cb_data);
 }
 
 /**
@@ -1064,19 +1050,12 @@ SR_API int sr_session_source_add_pollfd(struct sr_session *session,
                GPollFD *pollfd, int timeout, sr_receive_data_callback cb,
                void *cb_data)
 {
-       int ret;
-
        if (!pollfd) {
                sr_err("%s: pollfd was NULL", __func__);
                return SR_ERR_ARG;
        }
-       ret = sr_session_source_add_internal(session,
-                       timeout, cb, cb_data, (gintptr)pollfd);
-       if (ret != SR_OK)
-               return ret;
-
-       return sr_session_source_poll_add(session,
-                       (gintptr)pollfd, pollfd->fd, pollfd->events);
+       return attach_fd_source(session, pollfd, pollfd->fd,
+                       pollfd->events, timeout, cb, cb_data);
 }
 
 /**
@@ -1099,108 +1078,51 @@ SR_API int sr_session_source_add_channel(struct sr_session *session,
                GIOChannel *channel, int events, int timeout,
                sr_receive_data_callback cb, void *cb_data)
 {
-       int ret;
+       GPollFD pollfd;
 
-       ret = sr_session_source_add_internal(session,
-                       timeout, cb, cb_data, (gintptr)channel);
-       if (ret != SR_OK)
-               return ret;
+       if (!channel) {
+               sr_err("%s: channel was NULL", __func__);
+               return SR_ERR_ARG;
+       }
+       /* We should be using g_io_create_watch(), but can't without
+        * changing the driver API, as the callback signature is different.
+        */
 #ifdef G_OS_WIN32
-       GPollFD p;
-       g_io_channel_win32_make_pollfd(channel, events, &p);
-
-       return sr_session_source_poll_add(session,
-                       (gintptr)channel, p.fd, p.events);
+       g_io_channel_win32_make_pollfd(channel, events, &pollfd);
 #else
-       return sr_session_source_poll_add(session, (gintptr)channel,
-                       g_io_channel_unix_get_fd(channel), events);
+       pollfd.fd = g_io_channel_unix_get_fd(channel);
+       pollfd.events = events;
 #endif
+       return attach_fd_source(session, channel, pollfd.fd,
+                       pollfd.events, timeout, cb, cb_data);
 }
 
 /**
  * Remove the source identified by the specified poll object.
  *
  * @param session The session to use. Must not be NULL.
- * @param poll_object The channel for which the source should be removed.
+ * @param key The key by which the source is identified.
  *
  * @retval SR_OK Success
  * @retval SR_ERR_BUG No event source for poll_object found.
  */
 SR_PRIV int sr_session_source_remove_internal(struct sr_session *session,
-               gintptr poll_object)
+               void *key)
 {
-       struct source *source;
-       unsigned int i;
-       int fd_index = 0;
+       GSource *source;
 
-       for (i = 0; i < session->sources->len; ++i) {
-               source = &g_array_index(session->sources, struct source, i);
-
-               if (source->poll_object == poll_object) {
-                       if (source->num_fds > 0)
-                               g_array_remove_range(session->pollfds,
-                                               fd_index, source->num_fds);
-                       g_array_remove_index(session->sources, i);
-
-                       sr_dbg("Removed event source %" G_GINTPTR_FORMAT ".",
-                               poll_object);
-                       return SR_OK;
-               }
-               fd_index += source->num_fds;
-       }
-       /* Trying to remove an already removed event source is problematic
+       source = g_hash_table_lookup(session->event_sources, key);
+       /*
+        * Trying to remove an already removed event source is problematic
         * since the poll_object handle may have been reused in the meantime.
         */
-       sr_warn("Cannot remove non-existing event source %"
-               G_GINTPTR_FORMAT ".", poll_object);
-
-       return SR_ERR_BUG;
-}
-
-SR_PRIV int sr_session_source_poll_remove(struct sr_session *session,
-               gintptr poll_object, gintptr fd)
-{
-       struct source *source;
-       unsigned int i;
-       int fd_index, k;
-
-       source = NULL;
-       fd_index = 0;
-
-       /* Look up existing event source.
-        */
-       for (i = 0; i < session->sources->len; ++i) {
-               source = &g_array_index(session->sources, struct source, i);
-               if (source->poll_object == poll_object)
-                       break;
-               fd_index += source->num_fds;
-       }
        if (!source) {
-               sr_err("Cannot remove poll FD %" G_GINTPTR_FORMAT
-                       " from non-existing event source %" G_GINTPTR_FORMAT
-                       ".", fd, poll_object);
-               return SR_ERR;
+               sr_warn("Cannot remove non-existing event source %p.", key);
+               return SR_ERR_BUG;
        }
-       /* Look up the FD in the poll set.
-        */
-       for (k = 0; k < source->num_fds; ++k)
-               if (g_array_index(session->pollfds, GPollFD, fd_index + k)
-                               .fd == fd) {
+       g_source_destroy(source);
 
-                       g_array_remove_index(session->pollfds, fd_index + k);
-                       --source->num_fds;
-
-                       sr_dbg("Removed poll FD %" G_GINTPTR_FORMAT
-                               " from event source %" G_GINTPTR_FORMAT ".",
-                               fd, poll_object);
-                       return SR_OK;
-               }
-
-       sr_err("Cannot remove non-existing poll FD %" G_GINTPTR_FORMAT
-               " from event source %" G_GINTPTR_FORMAT ".",
-               fd, poll_object);
-
-       return SR_ERR;
+       return SR_OK;
 }
 
 /**
@@ -1217,7 +1139,7 @@ SR_PRIV int sr_session_source_poll_remove(struct sr_session *session,
  */
 SR_API int sr_session_source_remove(struct sr_session *session, int fd)
 {
-       return sr_session_source_remove_internal(session, fd);
+       return sr_session_source_remove_internal(session, GINT_TO_POINTER(fd));
 }
 
 /**
@@ -1239,7 +1161,7 @@ SR_API int sr_session_source_remove_pollfd(struct sr_session *session,
                sr_err("%s: pollfd was NULL", __func__);
                return SR_ERR_ARG;
        }
-       return sr_session_source_remove_internal(session, (gintptr)pollfd);
+       return sr_session_source_remove_internal(session, pollfd);
 }
 
 /**
@@ -1261,7 +1183,52 @@ SR_API int sr_session_source_remove_channel(struct sr_session *session,
                sr_err("%s: channel was NULL", __func__);
                return SR_ERR_ARG;
        }
-       return sr_session_source_remove_internal(session, (gintptr)channel);
+       return sr_session_source_remove_internal(session, channel);
+}
+
+/** Unregister an event source that has been destroyed.
+ *
+ * This is intended to be called from a source's finalize() method.
+ *
+ * @param session The session to use. Must not be NULL.
+ * @param key The key used to identify @a source.
+ * @param source The source object that was destroyed.
+ *
+ * @retval SR_OK Success.
+ * @retval SR_ERR_BUG Event source for @a key does not match @a source.
+ */
+SR_PRIV int sr_session_source_destroyed(struct sr_session *session,
+               void *key, GSource *source)
+{
+       GSource *registered_source;
+
+       registered_source = g_hash_table_lookup(session->event_sources, key);
+       /*
+        * Trying to remove an already removed event source is problematic
+        * since the poll_object handle may have been reused in the meantime.
+        */
+       if (!registered_source) {
+               sr_err("No event source for key %p found.", key);
+               return SR_ERR_BUG;
+       }
+       if (registered_source != source) {
+               sr_err("Event source for key %p does not match"
+                       " destroyed source.", key);
+               return SR_ERR_BUG;
+       }
+       g_hash_table_remove(session->event_sources, key);
+       /*
+        * Quit the main loop if we just removed the last event source.
+        * TODO: This may need an idle callback depending on when event
+        * sources are finalized. (The issue is remove followed by add
+        * within the same main loop iteration.)
+        */
+       if (session->main_loop
+                       && g_hash_table_size(session->event_sources) == 0) {
+               sr_dbg("Stopping main loop...");
+               g_main_loop_quit(session->main_loop);
+       }
+       return SR_OK;
 }
 
 static void copy_src(struct sr_config *src, struct sr_datafeed_meta *meta_copy)