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authorJeremy Allison <jra@samba.org>2013-02-11 11:40:49 -0800
committerJeremy Allison <jra@samba.org>2013-02-14 10:19:38 -0800
commit16f57076b1b527c65da42e1fab6119c67bcd7f47 (patch)
tree69d9a2363704af3396f2b7d0ad5f7fb9b6ec57f7 /lib
parent203f85c25eb9238eae8e4dc5b55b549294b0fa03 (diff)
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tevent: Add in the new implementation of "standard" tevent backend.
Falls back cleanly from epoll -> poll, or uses poll if epoll not available. Signed-off-by: Jeremy Allison <jra@samba.org> Signed-off-by: Stefan Metzmacher <metze@samba.org> Reviewed-by: Stefan Metzmacher <metze@samba.org>
Diffstat (limited to 'lib')
-rw-r--r--lib/tevent/tevent_standard.c186
1 files changed, 180 insertions, 6 deletions
diff --git a/lib/tevent/tevent_standard.c b/lib/tevent/tevent_standard.c
index 938b223572..0c72226558 100644
--- a/lib/tevent/tevent_standard.c
+++ b/lib/tevent/tevent_standard.c
@@ -2,7 +2,8 @@
Unix SMB/CIFS implementation.
main select loop and event handling
Copyright (C) Andrew Tridgell 2003-2005
- Copyright (C) Stefan Metzmacher 2005-2009
+ Copyright (C) Stefan Metzmacher 2005-2013
+ Copyright (C) Jeremy Allison 2013
** NOTE! The following LGPL license applies to the tevent
** library. This does NOT imply that all of Samba is released
@@ -26,18 +27,17 @@
This is SAMBA's default event loop code
- we try to use epoll if configure detected support for it
- otherwise we use select()
+ otherwise we use poll()
- if epoll is broken on the system or the kernel doesn't support it
- at runtime we fallback to select()
+ at runtime we fallback to poll()
*/
#include "replace.h"
-#include "system/filesys.h"
-#include "system/select.h"
#include "tevent.h"
#include "tevent_util.h"
#include "tevent_internal.h"
+#if 0
struct std_event_context {
/* a pointer back to the generic event_context */
struct tevent_context *ev;
@@ -589,10 +589,184 @@ static const struct tevent_ops std_event_ops = {
.loop_once = std_event_loop_once,
.loop_wait = tevent_common_loop_wait,
};
+#endif
+
+struct std_event_glue {
+ const struct tevent_ops *epoll_ops;
+ const struct tevent_ops *poll_ops;
+ struct tevent_ops *glue_ops;
+ bool fallback_replay;
+};
+
+static int std_event_context_init(struct tevent_context *ev);
+
+static const struct tevent_ops std_event_ops = {
+ .context_init = std_event_context_init,
+};
+
+/*
+ If this function gets called. epoll failed at runtime.
+ Move us to using poll instead. If we return false here,
+ caller should abort().
+*/
+static bool std_fallback_to_poll(struct tevent_context *ev, bool replay)
+{
+ void *glue_ptr = talloc_parent(ev->ops);
+ struct std_event_glue *glue =
+ talloc_get_type_abort(glue_ptr,
+ struct std_event_glue);
+ int ret;
+ struct tevent_fd *fde;
+ struct tevent_fd *fde_next;
+
+ glue->fallback_replay = replay;
+
+ /* First switch all the ops to poll. */
+ glue->epoll_ops = NULL;
+ TALLOC_FREE(ev->additional_data);
+
+ /*
+ * Set custom_ops the same as poll.
+ */
+ *glue->glue_ops = *glue->poll_ops;
+ glue->glue_ops->context_init = std_event_context_init;
+ /* Next initialize the poll backend. */
+ ret = glue->poll_ops->context_init(ev);
+ if (ret != 0) {
+ return false;
+ }
+
+ /*
+ * Now we have to change all the existing file descriptor
+ * events from the epoll backend to the poll backend.
+ */
+ for (fde = ev->fd_events; fde; fde = fde_next) {
+ /*
+ * We must remove this fde off the ev->fd_events list.
+ */
+ fde_next = fde->next;
+
+ /* Remove from the ev->fd_events list. */
+ DLIST_REMOVE(ev->fd_events, fde);
+
+ /* Re-add this event as a poll backend event. */
+ tevent_poll_event_add_fd_internal(ev, fde);
+ }
+
+ return true;
+}
+
+static int std_event_loop_once(struct tevent_context *ev, const char *location)
+{
+ void *glue_ptr = talloc_parent(ev->ops);
+ struct std_event_glue *glue =
+ talloc_get_type_abort(glue_ptr,
+ struct std_event_glue);
+ int ret;
+
+ ret = glue->epoll_ops->loop_once(ev, location);
+ if (glue->epoll_ops != NULL) {
+ /* No fallback */
+ return ret;
+ }
+
+ if (!glue->fallback_replay) {
+ /*
+ * The problem happened while modifying an event.
+ * An event handler was triggered in this case
+ * and there is no need to call loop_once() again.
+ */
+ return ret;
+ }
+
+ return glue->poll_ops->loop_once(ev, location);
+}
+
+/*
+ Initialize the epoll backend and allow it to call a
+ switch function if epoll fails at runtime.
+*/
+static int std_event_context_init(struct tevent_context *ev)
+{
+ struct std_event_glue *glue;
+ int ret;
+
+ /*
+ * If this is the first initialization
+ * we need to set up the allocated ops
+ * pointers.
+ */
+
+ if (ev->ops == &std_event_ops) {
+ glue = talloc_zero(ev, struct std_event_glue);
+ if (glue == NULL) {
+ return -1;
+ }
+
+ glue->epoll_ops = tevent_find_ops_byname("epoll");
+
+ glue->poll_ops = tevent_find_ops_byname("poll");
+ if (glue->poll_ops == NULL) {
+ return -1;
+ }
+
+ /*
+ * Allocate space for our custom ops.
+ * Allocate as a child of our epoll_ops pointer
+ * so we can easily get to it using talloc_parent.
+ */
+ glue->glue_ops = talloc_zero(glue, struct tevent_ops);
+ if (glue->glue_ops == NULL) {
+ talloc_free(glue);
+ return -1;
+ }
+
+ ev->ops = glue->glue_ops;
+ } else {
+ void *glue_ptr = talloc_parent(ev->ops);
+ glue = talloc_get_type_abort(glue_ptr, struct std_event_glue);
+ }
+
+ if (glue->epoll_ops != NULL) {
+ /*
+ * Set custom_ops the same as epoll,
+ * except re-init using std_event_context_init()
+ * and use std_event_loop_once() to add the
+ * ability to fallback to a poll backend on
+ * epoll runtime error.
+ */
+ *glue->glue_ops = *glue->epoll_ops;
+ glue->glue_ops->context_init = std_event_context_init;
+ glue->glue_ops->loop_once = std_event_loop_once;
+
+ ret = glue->epoll_ops->context_init(ev);
+ if (ret == -1) {
+ goto fallback;
+ }
+#ifdef HAVE_EPOLL
+ if (!tevent_epoll_set_panic_fallback(ev, std_fallback_to_poll)) {
+ TALLOC_FREE(ev->additional_data);
+ goto fallback;
+ }
+#endif
+
+ return ret;
+ }
+
+fallback:
+ glue->epoll_ops = NULL;
+
+ /*
+ * Set custom_ops the same as poll.
+ */
+ *glue->glue_ops = *glue->poll_ops;
+ glue->glue_ops->context_init = std_event_context_init;
+
+ return glue->poll_ops->context_init(ev);
+}
_PRIVATE_ bool tevent_standard_init(void)
{
return tevent_register_backend("standard", &std_event_ops);
}
-