A SCSI error handler and block runtime PM must not allocate
memory with GFP_KERNEL. Furthermore they must not wait for
tasks allocating memory with GFP_KERNEL.
That means that they cannot share a workqueue with arbitrary tasks.
Fix this for UAS using a private workqueue.
Signed-off-by: Oliver Neukum <oneukum@xxxxxxxx>
Fixes: f9dc024a2da1f ("uas: pre_reset and suspend: Fix a few races")
---
drivers/usb/storage/uas.c | 43 ++++++++++++++++++++++++++++++++++++++++---
1 file changed, 40 insertions(+), 3 deletions(-)
diff --git a/drivers/usb/storage/uas.c b/drivers/usb/storage/uas.c
index 08503e3507bf..d592071119ba 100644
--- a/drivers/usb/storage/uas.c
+++ b/drivers/usb/storage/uas.c
@@ -81,6 +81,19 @@ static void uas_free_streams(struct uas_dev_info *devinfo);
static void uas_log_cmd_state(struct scsi_cmnd *cmnd, const char *prefix,
int status);
+/*
+ * This driver needs its own workqueue, as we need to control memory allocation.
+ *
+ * In the course of error handling and power management uas_wait_for_pending_cmnds()
+ * needs to flush pending work items. In these contexts we cannot allocate memory
+ * by doing block IO as we would deadlock. For the same reason we cannot wait
+ * for anything allocating memory not heeding these constraints.
+ *
+ * So we have to control all work items that can be on the workqueue we flush.
+ * Hence we cannot share a queue and need our own.
+ */
+static struct workqueue_struct *workqueue;
+
static void uas_do_work(struct work_struct *work)
{
struct uas_dev_info *devinfo =
@@ -109,7 +122,7 @@ static void uas_do_work(struct work_struct *work)
if (!err)
cmdinfo->state &= ~IS_IN_WORK_LIST;
else
- schedule_work(&devinfo->work);
+ queue_work(workqueue, &devinfo->work);
}
out:
spin_unlock_irqrestore(&devinfo->lock, flags);
@@ -134,7 +147,7 @@ static void uas_add_work(struct uas_cmd_info *cmdinfo)
lockdep_assert_held(&devinfo->lock);
cmdinfo->state |= IS_IN_WORK_LIST;
- schedule_work(&devinfo->work);
+ queue_work(workqueue, &devinfo->work);
}
static void uas_zap_pending(struct uas_dev_info *devinfo, int result)
@@ -1229,7 +1242,31 @@ static struct usb_driver uas_driver = {
.id_table = uas_usb_ids,
};
-module_usb_driver(uas_driver);
+static int __init uas_init(void)
+{
+ int rv;
+
+ workqueue = alloc_workqueue("uas", WQ_MEM_RECLAIM, 0);
+ if (!workqueue)
+ return -ENOMEM;
+
+ rv = usb_register(&uas_driver);
+ if (rv) {
+ destroy_workqueue(workqueue);
+ return -ENOMEM;
+ }
+
+ return 0;
+}
+
+static void __exit uas_exit(void)
+{
+ usb_deregister(&uas_driver);
+ destroy_workqueue(workqueue);
+}
+
+module_init(uas_init);
+module_exit(uas_exit);
MODULE_LICENSE("GPL");
MODULE_IMPORT_NS(USB_STORAGE);
--
2.16.4
