Re: [PATCH v5 09/13] PCI: Introduce /sys/bus/pci/devices/.../remove

[Alex Chiang <achiang@hp.com>]

* Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>:
>
> I still have the following kernel error messages in testing with your
> latest set of patches (Jesse's linux-next). The test case is removing
> e1000e device or its parent bridge by "echo 1 > /sys/bus/pci/devices/
> .../remove".
>
> [  537.379995] =============================================
> [  537.380124] [ INFO: possible recursive locking detected ]
> [  537.380128] 2.6.29-rc8-kk #1
> [  537.380128] ---------------------------------------------
> [  537.380128] events/4/56 is trying to acquire lock:
> [  537.380128]  (events){--..}, at: [<ffffffff80257fc0>] flush_workqueue+0x0/0xa0
> [  537.380128]
> [  537.380128] but task is already holding lock:
> [  537.380128]  (events){--..}, at: [<ffffffff80257648>] run_workqueue+0x108/0x230
> [  537.380128]
> [  537.380128] other info that might help us debug this:
> [  537.380128] 3 locks held by events/4/56:
> [  537.380128]  #0:  (events){--..}, at: [<ffffffff80257648>] run_workqueue+0x108/0x230
> [  537.380128]  #1:  (&ss->work){--..}, at: [<ffffffff80257648>] run_workqueue+0x108/0x230
> [  537.380128]  #2:  (pci_remove_rescan_mutex){--..}, at: [<ffffffff803c10d1>] remove_callback+0x21/0x40

I still cannot reproduce this lockdep issue, even using your
.config with an e1000e device on an x86_64 kernel. :(

I tried removing the endpoint, an intermediate bridge device, and
the parent bus. I don't know what I'm doing wrong...

Can you please try this patch though, and see if it fixes the
warning? It applies on top of my other sysfs patch that
introduces a mutex in sysfs_schedule_callback.

Thanks.

/ac

diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
index 289c43a..7cc4dc0 100644
--- a/fs/sysfs/file.c
+++ b/fs/sysfs/file.c
@@ -667,6 +667,7 @@ struct sysfs_schedule_callback_struct {
 	struct work_struct	work;
 };
 
+static struct workqueue_struct *sysfs_workqueue;
 static DEFINE_MUTEX(sysfs_workq_mutex);
 static LIST_HEAD(sysfs_workq);
 static void sysfs_schedule_callback_work(struct work_struct *work)
@@ -720,6 +721,12 @@ int sysfs_schedule_callback(struct kobject *kobj, void (*func)(void *),
 		}
 	mutex_unlock(&sysfs_workq_mutex);
 
+	if (sysfs_workqueue == NULL) {
+		sysfs_workqueue = create_workqueue("sysfsqueue");
+		if (sysfs_workqueue == NULL)
+			return -ENOMEM;
+	}
+
 	ss = kmalloc(sizeof(*ss), GFP_KERNEL);
 	if (!ss) {
 		module_put(owner);
@@ -735,7 +742,7 @@ int sysfs_schedule_callback(struct kobject *kobj, void (*func)(void *),
 	mutex_lock(&sysfs_workq_mutex);
 	list_add_tail(&ss->workq_list, &sysfs_workq);
 	mutex_unlock(&sysfs_workq_mutex);
-	schedule_work(&ss->work);
+	queue_work(sysfs_workqueue, &ss->work);
 	return 0;
 }
 EXPORT_SYMBOL_GPL(sysfs_schedule_callback);