greybus: operation: make cancellation synchronous

Make sure to wait for the operation to become inactive before returning
after having cancelled an operation.

This makes sure that any ongoing operation completion callbacks have
finished.

Signed-off-by: Johan Hovold <johan@hovoldconsulting.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

diff --git a/drivers/staging/greybus/connection.c b/drivers/staging/greybus/connection.c
index 65a2bd5891d9959fd0753e3842a0696bd9310390..b9f9b11b1b65f2f335e2fbb14599ce038e8b0c83 100644 (file)
--- a/drivers/staging/greybus/connection.c
+++ b/drivers/staging/greybus/connection.c
@@ -227,7 +227,6 @@ void gb_connection_destroy(struct gb_connection *connection)
        if (WARN_ON(!connection))
                return;
 
-       /* XXX Need to wait for any outstanding requests to complete */
        if (WARN_ON(!list_empty(&connection->operations))) {
                list_for_each_entry_safe(operation, next,
                                         &connection->operations, links)

diff --git a/drivers/staging/greybus/operation.c b/drivers/staging/greybus/operation.c
index abe44c18fb9e2cc61234d96cc891ef52ed790f24..5e8ea0289053d7210512c728275ef4820e527cc6 100644 (file)
--- a/drivers/staging/greybus/operation.c
+++ b/drivers/staging/greybus/operation.c
@@ -10,6 +10,8 @@
 #include <linux/kernel.h>
 #include <linux/slab.h>
 #include <linux/module.h>
+#include <linux/sched.h>
+#include <linux/wait.h>
 #include <linux/workqueue.h>
 
 #include "greybus.h"
@@ -23,6 +25,9 @@ static struct kmem_cache *gb_message_cache;
 /* Workqueue to handle Greybus operation completions. */
 static struct workqueue_struct *gb_operation_workqueue;
 
+/* Wait queue for synchronous cancellations. */
+static DECLARE_WAIT_QUEUE_HEAD(gb_operation_cancellation_queue);
+
 /*
  * Protects access to connection operations lists, as well as
  * updates to operation->errno.
@@ -41,7 +46,15 @@ static inline void gb_operation_get_active(struct gb_operation *operation)
 /* Caller holds operation reference. */
 static inline void gb_operation_put_active(struct gb_operation *operation)
 {
-       atomic_dec(&operation->active);
+       if (atomic_dec_and_test(&operation->active)) {
+               if (atomic_read(&operation->waiters))
+                       wake_up(&gb_operation_cancellation_queue);
+       }
+}
+
+static inline bool gb_operation_is_active(struct gb_operation *operation)
+{
+       return atomic_read(&operation->active);
 }
 
 /*
@@ -463,6 +476,7 @@ gb_operation_create_common(struct gb_connection *connection, u8 type,
        init_completion(&operation->completion);
        kref_init(&operation->kref);
        atomic_set(&operation->active, 0);
+       atomic_set(&operation->waiters, 0);
 
        spin_lock_irqsave(&gb_operations_lock, flags);
        list_add_tail(&operation->links, &connection->operations);
@@ -873,7 +887,8 @@ void gb_connection_recv(struct gb_connection *connection,
 }
 
 /*
- * Cancel an operation, and record the given error to indicate why.
+ * Cancel an operation synchronously, and record the given error to indicate
+ * why.
  */
 void gb_operation_cancel(struct gb_operation *operation, int errno)
 {
@@ -890,6 +905,11 @@ void gb_operation_cancel(struct gb_operation *operation, int errno)
                        gb_operation_put(operation);
                }
        }
+
+       atomic_inc(&operation->waiters);
+       wait_event(gb_operation_cancellation_queue,
+                       !gb_operation_is_active(operation));
+       atomic_dec(&operation->waiters);
 }
 EXPORT_SYMBOL_GPL(gb_operation_cancel);
 

diff --git a/drivers/staging/greybus/operation.h b/drivers/staging/greybus/operation.h
index b32386636f6ecb1ae22fa285f29f1ab02750eadf..c8aaf90a006ac9be2db80adfab79797efb42bd64 100644 (file)
--- a/drivers/staging/greybus/operation.h
+++ b/drivers/staging/greybus/operation.h
@@ -128,6 +128,7 @@ struct gb_operation {
 
        struct kref             kref;
        atomic_t                active;
+       atomic_t                waiters;
 
        struct list_head        links;          /* connection->operations */
 };