On Mon, 29 Jan 2024, Tejun Heo wrote:
The only generic interface to execute asynchronously in the BH context is
tasklet; however, it's marked deprecated and has some design flaws. To
replace tasklets, BH workqueue support was recently added. A BH workqueue
behaves similarly to regular workqueues except that the queued work items
are executed in the BH context.
This patch converts usb hcd from tasklet to BH workqueue.
In the past this tasklet removal was held up by Mauro's device not properly
streaming - hopefully this no longer the case. Cc'ing.
https://lore.kernel.org/all/20180216170450.yl5owfphuvltstnt@xxxxxxxxxxxxx/
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
Cc: linux-usb@xxxxxxxxxxxxxxx
Acked-by: Davidlohr Bueso <dave@xxxxxxxxxxxx>
---
drivers/usb/core/hcd.c | 23 ++++++++++++-----------
include/linux/usb/hcd.h | 2 +-
2 files changed, 13 insertions(+), 12 deletions(-)
diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
index 12b6dfeaf658..edf74458474a 100644
--- a/drivers/usb/core/hcd.c
+++ b/drivers/usb/core/hcd.c
@@ -1664,9 +1664,10 @@ static void __usb_hcd_giveback_urb(struct urb *urb)
usb_put_urb(urb);
}
-static void usb_giveback_urb_bh(struct tasklet_struct *t)
+static void usb_giveback_urb_bh(struct work_struct *work)
{
- struct giveback_urb_bh *bh = from_tasklet(bh, t, bh);
+ struct giveback_urb_bh *bh =
+ container_of(work, struct giveback_urb_bh, bh);
struct list_head local_list;
spin_lock_irq(&bh->lock);
@@ -1691,9 +1692,9 @@ static void usb_giveback_urb_bh(struct tasklet_struct *t)
spin_lock_irq(&bh->lock);
if (!list_empty(&bh->head)) {
if (bh->high_prio)
- tasklet_hi_schedule(&bh->bh);
+ queue_work(system_bh_highpri_wq, &bh->bh);
else
- tasklet_schedule(&bh->bh);
+ queue_work(system_bh_wq, &bh->bh);
}
bh->running = false;
spin_unlock_irq(&bh->lock);
@@ -1706,7 +1707,7 @@ static void usb_giveback_urb_bh(struct tasklet_struct *t)
* @status: completion status code for the URB.
*
* Context: atomic. The completion callback is invoked in caller's context.
- * For HCDs with HCD_BH flag set, the completion callback is invoked in tasklet
+ * For HCDs with HCD_BH flag set, the completion callback is invoked in BH
* context (except for URBs submitted to the root hub which always complete in
* caller's context).
*
@@ -1725,7 +1726,7 @@ void usb_hcd_giveback_urb(struct usb_hcd *hcd, struct urb *urb, int status)
struct giveback_urb_bh *bh;
bool running;
- /* pass status to tasklet via unlinked */
+ /* pass status to BH via unlinked */
if (likely(!urb->unlinked))
urb->unlinked = status;
@@ -1747,9 +1748,9 @@ void usb_hcd_giveback_urb(struct usb_hcd *hcd, struct urb *urb, int status)
if (running)
;
else if (bh->high_prio)
- tasklet_hi_schedule(&bh->bh);
+ queue_work(system_bh_highpri_wq, &bh->bh);
else
- tasklet_schedule(&bh->bh);
+ queue_work(system_bh_wq, &bh->bh);
}
EXPORT_SYMBOL_GPL(usb_hcd_giveback_urb);
@@ -2540,7 +2541,7 @@ static void init_giveback_urb_bh(struct giveback_urb_bh *bh)
spin_lock_init(&bh->lock);
INIT_LIST_HEAD(&bh->head);
- tasklet_setup(&bh->bh, usb_giveback_urb_bh);
+ INIT_WORK(&bh->bh, usb_giveback_urb_bh);
}
struct usb_hcd *__usb_create_hcd(const struct hc_driver *driver,
@@ -2926,7 +2927,7 @@ int usb_add_hcd(struct usb_hcd *hcd,
&& device_can_wakeup(&hcd->self.root_hub->dev))
dev_dbg(hcd->self.controller, "supports USB remote wakeup\n");
- /* initialize tasklets */
+ /* initialize BHs */
init_giveback_urb_bh(&hcd->high_prio_bh);
hcd->high_prio_bh.high_prio = true;
init_giveback_urb_bh(&hcd->low_prio_bh);
@@ -3036,7 +3037,7 @@ void usb_remove_hcd(struct usb_hcd *hcd)
mutex_unlock(&usb_bus_idr_lock);
/*
- * tasklet_kill() isn't needed here because:
+ * flush_work() isn't needed here because:
* - driver's disconnect() called from usb_disconnect() should
* make sure its URBs are completed during the disconnect()
* callback
diff --git a/include/linux/usb/hcd.h b/include/linux/usb/hcd.h
index 00724b4f6e12..f698aac71de3 100644
--- a/include/linux/usb/hcd.h
+++ b/include/linux/usb/hcd.h
@@ -55,7 +55,7 @@ struct giveback_urb_bh {
bool high_prio;
spinlock_t lock;
struct list_head head;
- struct tasklet_struct bh;
+ struct work_struct bh;
struct usb_host_endpoint *completing_ep;
};
--
2.43.0
