lib: tevent: Initial checkin of threaded tevent context calling code.

Adds 2 new functions:

struct tevent_thread_proxy *tevent_thread_proxy_create(
                struct tevent_context *dest_ev_ctx);

void tevent_thread_proxy_schedule(struct tevent_thread_proxy *tp,
		struct tevent_immediate **pp_im,
		tevent_immediate_handler_t handler,
		void *pp_private_data);

Brief doc included. Tests, docs and tutorial to follow.

Signed-off-by: Jeremy Allison <jra@samba.org>
Signed-off-by: Ralph Boehme <slow@samba.org>
Reviewed-by: Stefan Metzmacher <metze@samba.org>

3 files changed, 423 insertions, 1 deletions

diff --git a/lib/tevent/tevent.h b/lib/tevent/tevent.h
index b6c39d1037b..cb955077938 100644
--- a/lib/tevent/tevent.h
+++ b/lib/tevent/tevent.h
@@ -39,6 +39,7 @@ struct tevent_fd;
 struct tevent_timer;
 struct tevent_immediate;
 struct tevent_signal;
+struct tevent_thread_proxy;
 
 /**
  * @defgroup tevent The tevent API
@@ -1698,6 +1699,57 @@ typedef int (*tevent_nesting_hook)(struct tevent_context *ev,
 				   bool begin,
 				   void *stack_ptr,
 				   const char *location);
+
+/**
+ * @brief Create a tevent_thread_proxy for message passing between threads.
+ *
+ * The tevent_context must have been allocated on the NULL
+ * talloc context, and talloc_disable_null_tracking() must
+ * have been called.
+ *
+ * @param[in]  dest_ev_ctx      The tevent_context to receive events.
+ *
+ * @return              An allocated tevent_thread_proxy, NULL on error.
+ *                      If tevent was compiled without PTHREAD support
+ *                      NULL is always returned and errno set to ENOSYS.
+ *
+ * @see tevent_thread_proxy_schedule()
+ */
+struct tevent_thread_proxy *tevent_thread_proxy_create(
+                struct tevent_context *dest_ev_ctx);
+
+/**
+ * @brief Schedule an immediate event on an event context from another thread.
+ *
+ * Causes dest_ev_ctx, being run by another thread, to receive an
+ * immediate event calling the handler with the *pp_private parameter.
+ *
+ * *pp_im must be a pointer to an immediate event talloced on a context owned
+ * by the calling thread, or the NULL context. Ownership will
+ * be transferred to the tevent_thread_proxy and *pp_im will be returned as NULL.
+ *
+ * *pp_private_data must be a talloced area of memory with no destructors.
+ * Ownership of this memory will be transferred to the tevent library and
+ * *pp_private_data will be set to NULL on successful completion of
+ * the call. Set pp_private to NULL if no parameter transfer
+ * needed (a pure callback). This is an asynchronous request, caller
+ * does not wait for callback to be completed before returning.
+ *
+ * @param[in]  tp               The tevent_thread_proxy to use.
+ *
+ * @param[in]  pp_im            Pointer to immediate event pointer.
+ *
+ * @param[in]  handler          The function that will be called.
+ *
+ * @param[in]  pp_private_data  The talloced memory to transfer.
+ *
+ * @see tevent_thread_proxy_create()
+ */
+void tevent_thread_proxy_schedule(struct tevent_thread_proxy *tp,
+				  struct tevent_immediate **pp_im,
+				  tevent_immediate_handler_t handler,
+				  void *pp_private_data);
+
 #ifdef TEVENT_DEPRECATED
 #ifndef _DEPRECATED_
 #if (__GNUC__ >= 3) && (__GNUC_MINOR__ >= 1 )
diff --git a/lib/tevent/tevent_threads.c b/lib/tevent/tevent_threads.c
new file mode 100644
index 00000000000..8d44e4f8f5f
--- /dev/null
+++ b/lib/tevent/tevent_threads.c
@@ -0,0 +1,370 @@
+/*
+   tevent event library.
+
+   Copyright (C) Jeremy Allison 2015
+
+     ** NOTE! The following LGPL license applies to the tevent
+     ** library. This does NOT imply that all of Samba is released
+     ** under the LGPL
+
+   This library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 3 of the License, or (at your option) any later version.
+
+   This library 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
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with this library; if not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "replace.h"
+#include "system/filesys.h"
+#include "talloc.h"
+#include "tevent.h"
+#include "tevent_internal.h"
+#include "tevent_util.h"
+
+#if defined(HAVE_PTHREAD)
+#include <pthread.h>
+
+struct tevent_immediate_list {
+	struct tevent_immediate_list *next, *prev;
+	tevent_immediate_handler_t handler;
+	struct tevent_immediate *im;
+	void *private_ptr;
+};
+
+struct tevent_thread_proxy {
+	pthread_mutex_t mutex;
+	struct tevent_context *dest_ev_ctx;
+	int read_fd;
+	int write_fd;
+	struct tevent_fd *pipe_read_fde;
+	/* Pending events list. */
+	struct tevent_immediate_list *im_list;
+	/* Completed events list. */
+	struct tevent_immediate_list *tofree_im_list;
+	struct tevent_immediate *free_im;
+};
+
+static void free_im_list(struct tevent_immediate_list **pp_list_head)
+{
+	struct tevent_immediate_list *im_entry = NULL;
+	struct tevent_immediate_list *im_next = NULL;
+
+	for (im_entry = *pp_list_head; im_entry; im_entry = im_next) {
+		im_next = im_entry->next;
+		DLIST_REMOVE(*pp_list_head, im_entry);
+		TALLOC_FREE(im_entry);
+	}
+}
+
+static void free_list_handler(struct tevent_context *ev,
+				struct tevent_immediate *im,
+				void *private_ptr)
+{
+	struct tevent_thread_proxy *tp =
+		talloc_get_type_abort(private_ptr, struct tevent_thread_proxy);
+	int ret;
+
+	ret = pthread_mutex_lock(&tp->mutex);
+	if (ret != 0) {
+		abort();
+		/* Notreached. */
+		return;
+	}
+
+	free_im_list(&tp->tofree_im_list);
+
+	ret = pthread_mutex_unlock(&tp->mutex);
+	if (ret != 0) {
+		abort();
+		/* Notreached. */
+		return;
+	}
+}
+
+static void schedule_immediate_functions(struct tevent_thread_proxy *tp)
+{
+	struct tevent_immediate_list *im_entry = NULL;
+	struct tevent_immediate_list *im_next = NULL;
+
+	for (im_entry = tp->im_list; im_entry; im_entry = im_next) {
+		im_next = im_entry->next;
+		DLIST_REMOVE(tp->im_list, im_entry);
+
+		tevent_schedule_immediate(im_entry->im,
+					tp->dest_ev_ctx,
+					im_entry->handler,
+					im_entry->private_ptr);
+
+		/* Move from pending list to free list. */
+		DLIST_ADD(tp->tofree_im_list, im_entry);
+	}
+	if (tp->tofree_im_list != NULL) {
+		/*
+		 * Once the current immediate events
+		 * are processed, we need to reshedule
+		 * ourselves to free them. This works
+		 * as tevent_schedule_immediate()
+		 * always adds events to the *END* of
+		 * the immediate events list.
+		 */
+		tevent_schedule_immediate(tp->free_im,
+					tp->dest_ev_ctx,
+					free_list_handler,
+					tp);
+	}
+}
+
+static void pipe_read_handler(struct tevent_context *ev,
+				struct tevent_fd *fde,
+				uint16_t flags,
+				void *private_ptr)
+{
+	struct tevent_thread_proxy *tp =
+		talloc_get_type_abort(private_ptr, struct tevent_thread_proxy);
+	ssize_t len = 64;
+	int ret;
+
+	ret = pthread_mutex_lock(&tp->mutex);
+	if (ret != 0) {
+		abort();
+		/* Notreached. */
+		return;
+	}
+
+	/*
+	 * Clear out all data in the pipe. We
+	 * don't really care if this returns -1.
+	 */
+	while (len == 64) {
+		char buf[64];
+		len = read(tp->read_fd, buf, 64);
+	};
+
+	schedule_immediate_functions(tp);
+
+	ret = pthread_mutex_unlock(&tp->mutex);
+	if (ret != 0) {
+		abort();
+		/* Notreached. */
+		return;
+	}
+}
+
+static int tevent_thread_proxy_destructor(struct tevent_thread_proxy *tp)
+{
+	int ret;
+
+	ret = pthread_mutex_lock(&tp->mutex);
+	if (ret != 0) {
+		abort();
+		/* Notreached. */
+		return 0;
+	}
+
+	TALLOC_FREE(tp->pipe_read_fde);
+
+	if (tp->read_fd != -1) {
+		(void)close(tp->read_fd);
+		tp->read_fd = -1;
+	}
+	if (tp->write_fd != -1) {
+		(void)close(tp->write_fd);
+		tp->write_fd = -1;
+	}
+
+	/* Hmmm. It's probably an error if we get here with
+	   any non-NULL immediate entries.. */
+
+	free_im_list(&tp->im_list);
+	free_im_list(&tp->tofree_im_list);
+
+	TALLOC_FREE(tp->free_im);
+
+	ret = pthread_mutex_unlock(&tp->mutex);
+	if (ret != 0) {
+		abort();
+		/* Notreached. */
+		return 0;
+	}
+
+	ret = pthread_mutex_destroy(&tp->mutex);
+	if (ret != 0) {
+		abort();
+		/* Notreached. */
+		return 0;
+	}
+
+	return 0;
+}
+
+/*
+ * Create a struct that can be passed to other threads
+ * to allow them to signal the struct tevent_context *
+ * passed in.
+ */
+
+struct tevent_thread_proxy *tevent_thread_proxy_create(
+		struct tevent_context *dest_ev_ctx)
+{
+	int ret;
+	int pipefds[2];
+	struct tevent_thread_proxy *tp;
+
+	tp = talloc_zero(dest_ev_ctx, struct tevent_thread_proxy);
+	if (tp == NULL) {
+		return NULL;
+	}
+
+	ret = pthread_mutex_init(&tp->mutex, NULL);
+	if (ret != 0) {
+		goto fail;
+	}
+
+	tp->dest_ev_ctx = dest_ev_ctx;
+	tp->read_fd = -1;
+	tp->write_fd = -1;
+
+	talloc_set_destructor(tp, tevent_thread_proxy_destructor);
+
+	ret = pipe(pipefds);
+	if (ret == -1) {
+		goto fail;
+	}
+
+	tp->read_fd = pipefds[0];
+	tp->write_fd = pipefds[1];
+
+	ret = ev_set_blocking(pipefds[0], false);
+	if (ret != 0) {
+		goto fail;
+	}
+	ret = ev_set_blocking(pipefds[1], false);
+	if (ret != 0) {
+		goto fail;
+	}
+	if (!ev_set_close_on_exec(pipefds[0])) {
+		goto fail;
+	}
+	if (!ev_set_close_on_exec(pipefds[1])) {
+		goto fail;
+	}
+
+	tp->pipe_read_fde = tevent_add_fd(dest_ev_ctx,
+				tp,
+				tp->read_fd,
+				TEVENT_FD_READ,
+				pipe_read_handler,
+				tp);
+	if (tp->pipe_read_fde == NULL) {
+		goto fail;
+	}
+
+	/*
+	 * Create an immediate event to free
+	 * completed lists.
+	 */
+	tp->free_im = tevent_create_immediate(tp);
+	if (tp->free_im == NULL) {
+		goto fail;
+	}
+
+	return tp;
+
+  fail:
+
+	TALLOC_FREE(tp);
+	return NULL;
+}
+
+/*
+ * This function schedules an immediate event to be called with argument
+ * *pp_private in the thread context of dest_ev_ctx. Caller doesn't
+ * wait for activation to take place, this is simply fire-and-forget.
+ *
+ * pp_im must be a pointer to an immediate event talloced on
+ * a context owned by the calling thread, or the NULL context.
+ * Ownership of *pp_im will be transfered to the tevent library.
+ *
+ * pp_private can be null, or contents of *pp_private must be
+ * talloc'ed memory on a context owned by the calling thread
+ * or the NULL context. If non-null, ownership of *pp_private will
+ * be transfered to the tevent library.
+ *
+ * If you want to return a message, have the destination use the
+ * same function call to send back to the caller.
+ */
+
+
+void tevent_thread_proxy_schedule(struct tevent_thread_proxy *tp,
+				  struct tevent_immediate **pp_im,
+				  tevent_immediate_handler_t handler,
+				  void *pp_private_data)
+{
+	struct tevent_immediate_list *im_entry;
+	int ret;
+	char c;
+
+	ret = pthread_mutex_lock(&tp->mutex);
+	if (ret != 0) {
+		abort();
+		/* Notreached. */
+		return;
+	}
+
+	if (tp->write_fd == -1) {
+		/* In the process of being destroyed. Ignore. */
+		goto end;
+	}
+
+	/* Create a new immediate_list entry. MUST BE ON THE NULL CONTEXT */
+	im_entry = talloc_zero(NULL, struct tevent_immediate_list);
+	if (im_entry == NULL) {
+		goto end;
+	}
+
+	im_entry->handler = handler;
+	im_entry->im = talloc_move(im_entry, pp_im);
+
+	if (pp_private_data != NULL) {
+		void **pptr = (void **)pp_private_data;
+		im_entry->private_ptr = talloc_move(im_entry, pptr);
+	}
+
+	DLIST_ADD(tp->im_list, im_entry);
+
+	/* And notify the dest_ev_ctx to wake up. */
+	c = '\0';
+	(void)write(tp->write_fd, &c, 1);
+
+  end:
+
+	ret = pthread_mutex_unlock(&tp->mutex);
+	if (ret != 0) {
+		abort();
+		/* Notreached. */
+	}
+}
+#else
+/* !HAVE_PTHREAD */
+struct tevent_thread_proxy *tevent_thread_proxy_create(
+		struct tevent_context *dest_ev_ctx)
+{
+	errno = ENOSYS;
+	return NULL;
+}
+
+void tevent_thread_proxy_schedule(struct tevent_thread_proxy *tp,
+				  struct tevent_immediate **pp_im,
+				  tevent_immediate_handler_t handler,
+				  void *pp_private_data)
+{
+	;
+}
+#endif
diff --git a/lib/tevent/wscript b/lib/tevent/wscript
index 827094c472a..d41e7e73ef6 100755
--- a/lib/tevent/wscript
+++ b/lib/tevent/wscript
@@ -83,7 +83,7 @@ def build(bld):
 
     SRC = '''tevent.c tevent_debug.c tevent_fd.c tevent_immediate.c
              tevent_queue.c tevent_req.c tevent_select.c
-             tevent_poll.c
+             tevent_poll.c tevent_threads.c
              tevent_signal.c tevent_standard.c tevent_timed.c tevent_util.c tevent_wakeup.c'''
 
     if bld.CONFIG_SET('HAVE_EPOLL'):