firewire: clean up fw_card reference counting

This is a functionally equivalent replacement of the current reference
counting of struct fw_card instances.  It only converts it to common
idioms as suggested by Kristian Høgsberg:
  - struct kref replaces atomic_t as the counter.
  - wait_for_completion is used to wait for all card users to complete.

BTW, it may make sense to count card->flush_timer and card->work as
card users too.

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>

1 files changed, 20 insertions, 10 deletions

diff --git a/drivers/firewire/fw-card.c b/drivers/firewire/fw-card.c
index 1332b66ae0b3..da873d795aad 100644
--- a/drivers/firewire/fw-card.c
+++ b/drivers/firewire/fw-card.c
@@ -16,12 +16,15 @@
  * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  */
 
-#include <linux/module.h>
-#include <linux/errno.h>
+#include <linux/completion.h>
+#include <linux/crc-itu-t.h>
 #include <linux/delay.h>
 #include <linux/device.h>
+#include <linux/errno.h>
+#include <linux/kref.h>
+#include <linux/module.h>
 #include <linux/mutex.h>
-#include <linux/crc-itu-t.h>
+
 #include "fw-transaction.h"
 #include "fw-topology.h"
 #include "fw-device.h"
@@ -396,7 +399,6 @@ fw_card_initialize(struct fw_card *card, const struct fw_card_driver *driver,
 {
         static atomic_t index = ATOMIC_INIT(-1);
 
-        atomic_set(&card->device_count, 0);
         card->index = atomic_inc_return(&index);
         card->driver = driver;
         card->device = device;
@@ -405,6 +407,8 @@ fw_card_initialize(struct fw_card *card, const struct fw_card_driver *driver,
         card->color = 0;
         card->broadcast_channel = BROADCAST_CHANNEL_INITIAL;
 
+        kref_init(&card->kref);
+        init_completion(&card->done);
         INIT_LIST_HEAD(&card->transaction_list);
         spin_lock_init(&card->lock);
         setup_timer(&card->flush_timer,
@@ -507,6 +511,14 @@ static struct fw_card_driver dummy_driver = {
 };
 
 void
+fw_card_release(struct kref *kref)
+{
+        struct fw_card *card = container_of(kref, struct fw_card, kref);
+
+        complete(&card->done);
+}
+
+void
 fw_core_remove_card(struct fw_card *card)
 {
         card->driver->update_phy_reg(card, 4,
@@ -521,12 +533,10 @@ fw_core_remove_card(struct fw_card *card)
         card->driver = &dummy_driver;
 
         fw_destroy_nodes(card);
-        /*
-         * Wait for all device workqueue jobs to finish.  Otherwise the
-         * firewire-core module could be unloaded before the jobs ran.
-         */
-        while (atomic_read(&card->device_count) > 0)
-                msleep(100);
+
+        /* Wait for all users, especially device workqueue jobs, to finish. */
+        fw_card_put(card);
+        wait_for_completion(&card->done);
 
         cancel_delayed_work_sync(&card->work);
         fw_flush_transactions(card);