discover: Add load_url_cancel

We'd like a way to cancel pending loads, as part of aborting the boot
process.

Signed-off-by: Jeremy Kerr <jk@ozlabs.org>

2 files changed, 38 insertions, 4 deletions

diff --git a/discover/paths.c b/discover/paths.c
index c352ca0..aa977fd 100644
--- a/discover/paths.c
+++ b/discover/paths.c
@@ -1,5 +1,6 @@
 #define _GNU_SOURCE
 
+#include <assert.h>
 #include <string.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -79,9 +80,14 @@ static void load_url_process_exit(struct process *process)
 	data = task->async_data;
 	cb = task->async_cb;
 
-	result->status = process->exit_status == 0 ? LOAD_OK : LOAD_ERROR;
-	if (result->status == LOAD_ERROR)
+	if (result->status == LOAD_CANCELLED) {
 		load_url_result_cleanup_local(result);
+	} else if (process->exit_status == 0) {
+		result->status = LOAD_OK;
+	} else {
+		result->status = LOAD_ERROR;
+		load_url_result_cleanup_local(result);
+	}
 
 	/* The load callback may well free the ctx, which was the
 	 * talloc parent of the task. Therefore, we want to do our cleanup
@@ -89,6 +95,7 @@ static void load_url_process_exit(struct process *process)
 	 */
 	process_release(process);
 	talloc_free(task);
+	result->task = NULL;
 
 	cb(result, data);
 }
@@ -359,6 +366,7 @@ struct load_url_result *load_url_async(void *ctx, struct pb_url *url,
 	task->url = url;
 	task->async = async_cb != NULL;
 	task->result = talloc_zero(ctx, struct load_url_result);
+	task->result->task = task;
 	task->process = process_create(task);
 	if (task->async) {
 		task->async_cb = async_cb;
@@ -407,3 +415,22 @@ struct load_url_result *load_url(void *ctx, struct pb_url *url)
 {
 	return load_url_async(ctx, url, NULL, NULL);
 }
+
+void load_url_async_cancel(struct load_url_result *res)
+{
+	struct load_task *task = res->task;
+
+	/* the completion callback may have already been called; this clears
+	 * res->task */
+	if (!task)
+		return;
+
+	if (res->status == LOAD_CANCELLED)
+		return;
+
+	assert(task->async);
+	assert(task->process);
+
+	res->status = LOAD_CANCELLED;
+	process_stop_async(task->process);
+}
diff --git a/discover/paths.h b/discover/paths.h
index e905094..ed0e153 100644
--- a/discover/paths.h
+++ b/discover/paths.h
@@ -16,6 +16,7 @@ char *join_paths(void *alloc_ctx, const char *a, const char *b);
  */
 const char *mount_base(void);
 
+struct load_task;
 
 struct load_url_result {
 	enum {
@@ -26,9 +27,12 @@ struct load_url_result {
 			     * (sync will see a NULL result) */
 
 		LOAD_ASYNC, /* async load still in progress */
+
+		LOAD_CANCELLED,
 	} status;
-	const char	*local;
-	bool		cleanup_local;
+	const char		*local;
+	bool			cleanup_local;
+	struct load_task	*task;
 };
 
 /* callback type for asynchronous loads. The callback implementation is
@@ -40,6 +44,9 @@ typedef void (*load_url_complete)(struct load_url_result *result, void *data);
 struct load_url_result *load_url_async(void *ctx, struct pb_url *url,
 		load_url_complete complete, void *data);
 
+/* Cancel a pending load */
+void load_url_async_cancel(struct load_url_result *res);
+
 struct load_url_result *load_url(void *ctx, struct pb_url *url);
 
 #endif /* PATHS_H */