1 files changed, 146 insertions, 38 deletions

diff --git a/src/include/gpxe/async.h b/src/include/gpxe/async.h
index 8a6819786..d3b075b92 100644
--- a/src/include/gpxe/async.h
+++ b/src/include/gpxe/async.h
@@ -7,56 +7,164 @@
  *
  */
 
-#include <errno.h>
-#include <assert.h>
+#include <gpxe/list.h>
 
-/** An asynchronous operation */
-struct async_operation {
-	/** Operation status
-	 *
-	 * This is an error code as defined in errno.h, plus an offset
-	 * of EINPROGRESS.  This means that a status value of 0
-	 * corresponds to a return status code of -EINPROGRESS,
-	 * i.e. that the default state of an asynchronous operation is
-	 * "not yet completed".
-	 */
-	int status;
-};
+struct async;
 
-/**
- * Set asynchronous operation status
+/** An asynchronous operation ID
  *
- * @v aop	Asynchronous operation
- * @v rc	Return status code
+ * Only positive identifiers are valid; negative values are used to
+ * indicate errors.
  */
-static inline __attribute__ (( always_inline )) void
-async_set_status ( struct async_operation *aop, int rc ) {
-	aop->status = ( rc + EINPROGRESS );
-}
+typedef long aid_t;
+
+/** Signals that can be delivered to asynchronous operations */
+enum signal {
+	/** A child asynchronous operation has completed
+	 *
+	 * The parent should call async_wait() to reap the completed
+	 * child.  async_wait() will return the exit status and
+	 * operation identifier of the child.
+	 *
+	 * The handler for this signal can be set to @c NULL; if it
+	 * is, then the children will accumulate as zombies until
+	 * async_wait() is called.
+	 *
+	 * The handler for this signal can also be set to @c SIG_IGN;
+	 * if it is, then the children will automatically be reaped.
+	 * Note that if you use @c SIG_IGN then you will not be able
+	 * to retrieve the return status of the children; the call to
+	 * async_wait() will simply return -ECHILD.
+	 */
+	SIGCHLD = 0,
+	/** Cancel asynchronous operation
+	 *
+	 * This signal should trigger the asynchronous operation to
+	 * cancel itself (including killing all its own children, if
+	 * any), and then call async_done().  The asynchronous
+	 * operation is allowed to not complete immediately.
+	 *
+	 * The handler for this signal can be set to @c NULL; if it
+	 * is, then attempts to cancel the asynchronous operation will
+	 * fail and the operation will complete normally.  Anything
+	 * waiting for the operation to cancel will block.
+	 */
+	SIGKILL,
+	/** Update progress of asynchronous operation
+	 *
+	 * This signal should cause the asynchronous operation to
+	 * immediately update the @c completed and @c total fields.
+	 *
+	 * The handler for this signal can be set to @c NULL; if it
+	 * is, then the asynchronous operation is expected to keep its
+	 * @c completed and @c total fields up to date at all times.
+	 */
+	SIGUPDATE,
+	SIGMAX
+};
 
 /**
- * Get asynchronous operation status
+ * A signal handler
  *
- * @v aop	Asynchronous operation
- * @ret rc	Return status code
+ * @v async		Asynchronous operation
+ * @v signal		Signal received
  */
-static inline __attribute__ (( always_inline )) int
-async_status ( struct async_operation *aop ) {
-	return ( aop->status - EINPROGRESS );
-}
+typedef void ( * signal_handler_t ) ( struct async *async,
+				      enum signal signal );
+
+/** Asynchronous operation operations */
+struct async_operations {
+	/** Reap asynchronous operation
+	 *
+	 * @v async		Asynchronous operation
+	 *
+	 * Release all resources associated with the asynchronous
+	 * operation.  This will be called only after the asynchronous
+	 * operation itself calls async_done(), so the only remaining
+	 * resources will probably be the memory used by the struct
+	 * async itself.
+	 *
+	 * This method can be set to @c NULL; if it is, then no
+	 * resources will be freed.  This may be suitable for
+	 * asynchronous operations that consume no dynamically
+	 * allocated memory.
+	 */
+	void ( * reap ) ( struct async *async );
+	/** Handle signals */
+	signal_handler_t signal[SIGMAX];
+};
+
+/** An asynchronous operation */
+struct async {
+	/** Other asynchronous operations with the same parent */
+	struct list_head siblings;
+	/** Child asynchronous operations */
+	struct list_head children;
+	/** Parent asynchronous operation
+	 *
+	 * This field is optional; if left to NULL then the owner must
+	 * never call async_done().
+	 */
+	struct async *parent;
+	/** Asynchronous operation ID */
+	aid_t aid;
+	/** Final return status code */
+	int rc;
+
+	/** Amount of operation completed so far
+	 *
+	 * The units for this quantity are arbitrary.  @c completed
+	 * divded by @total should give something which approximately
+	 * represents the progress through the operation.  For a
+	 * download operation, using byte counts would make sense.
+	 *
+	 * This progress indicator should also incorporate the status
+	 * of any child asynchronous operations.
+	 */
+	unsigned long completed;
+	/** Total operation size
+	 *
+	 * See @c completed.  A zero value means "total size unknown"
+	 * and is explcitly permitted; users should take this into
+	 * account before calculating @c completed/total.
+	 */
+	unsigned long total;
+
+	struct async_operations *aop;
+};
+
+extern struct async_operations default_async_operations;
+extern struct async_operations orphan_async_operations;
+
+extern aid_t async_init ( struct async *async, struct async_operations *aop,
+			  struct async *parent );
+extern void async_ignore_signal ( struct async *async, enum signal signal );
+extern void async_signal ( struct async *async, enum signal signal );
+extern void async_signal_children ( struct async *async, enum signal signal );
+extern void async_done ( struct async *async, int rc );
+extern aid_t async_wait ( struct async *async, int *rc, int block );
+
+/** Default signal handler */
+#define SIG_DFL NULL
+
+/** Ignore signal */
+#define SIG_IGN async_ignore_signal
 
 /**
- * Flag asynchronous operation as complete
+ * Initialise orphan asynchronous operation
  *
- * @v aop	Asynchronous operation
- * @v rc	Return status code
+ * @v async		Asynchronous operation
+ * @ret aid		Asynchronous operation ID
+ *
+ * An orphan asynchronous operation can act as a context for child
+ * operations.  However, you must not call async_done() on such an
+ * operation, since this would attempt to send a signal to its
+ * (non-existent) parent.  Instead, simply free the structure (after
+ * calling async_wait() to ensure that any child operations have
+ * completed).
  */
-static inline __attribute__ (( always_inline )) void
-async_done ( struct async_operation *aop, int rc ) {
-	assert ( rc != -EINPROGRESS );
-	async_set_status ( aop, rc );
+static inline aid_t async_init_orphan ( struct async *async ) {
+	return async_init ( async, &orphan_async_operations, NULL );
 }
 
-extern int async_wait ( struct async_operation *aop );
-
 #endif /* _GPXE_ASYNC_H */