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usb: core: hcd: Convert from tasklet to BH workqueue

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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.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: linux-usb@vger.kernel.org
This commit is contained in:
Tejun Heo 2024-02-04 11:34:34 -10:00
parent 7245d24f87
commit 8fea0c8fda
2 changed files with 13 additions and 12 deletions
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23
drivers/usb/core/hcd.c
View file

@ -1664,9 +1664,10 @@ static void __usb_hcd_giveback_urb(struct urb *urb)
usb_put_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; struct list_head local_list;
spin_lock_irq(&bh->lock); spin_lock_irq(&bh->lock);
@ -1691,9 +1692,9 @@ static void usb_giveback_urb_bh(struct tasklet_struct *t)
spin_lock_irq(&bh->lock); spin_lock_irq(&bh->lock);
if (!list_empty(&bh->head)) { if (!list_empty(&bh->head)) {
if (bh->high_prio) if (bh->high_prio)
tasklet_hi_schedule(&bh->bh); queue_work(system_bh_highpri_wq, &bh->bh);
else else
tasklet_schedule(&bh->bh); queue_work(system_bh_wq, &bh->bh);
} }
bh->running = false; bh->running = false;
spin_unlock_irq(&bh->lock); 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. * @status: completion status code for the URB.
* *
* Context: atomic. The completion callback is invoked in caller's context. * 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 * context (except for URBs submitted to the root hub which always complete in
* caller's context). * 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; struct giveback_urb_bh *bh;
bool running; bool running;
/* pass status to tasklet via unlinked */ /* pass status to BH via unlinked */
if (likely(!urb->unlinked)) if (likely(!urb->unlinked))
urb->unlinked = status; urb->unlinked = status;
@ -1747,9 +1748,9 @@ void usb_hcd_giveback_urb(struct usb_hcd *hcd, struct urb *urb, int status)
if (running) if (running)
; ;
else if (bh->high_prio) else if (bh->high_prio)
tasklet_hi_schedule(&bh->bh); queue_work(system_bh_highpri_wq, &bh->bh);
else else
tasklet_schedule(&bh->bh); queue_work(system_bh_wq, &bh->bh);
} }
EXPORT_SYMBOL_GPL(usb_hcd_giveback_urb); 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); spin_lock_init(&bh->lock);
INIT_LIST_HEAD(&bh->head); 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, 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)) && device_can_wakeup(&hcd->self.root_hub->dev))
dev_dbg(hcd->self.controller, "supports USB remote wakeup\n"); dev_dbg(hcd->self.controller, "supports USB remote wakeup\n");
/* initialize tasklets */ /* initialize BHs */
init_giveback_urb_bh(&hcd->high_prio_bh); init_giveback_urb_bh(&hcd->high_prio_bh);
hcd->high_prio_bh.high_prio = true; hcd->high_prio_bh.high_prio = true;
init_giveback_urb_bh(&hcd->low_prio_bh); 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); 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 * - driver's disconnect() called from usb_disconnect() should
* make sure its URBs are completed during the disconnect() * make sure its URBs are completed during the disconnect()
* callback * callback

2
include/linux/usb/hcd.h
View file

@ -55,7 +55,7 @@ struct giveback_urb_bh {
bool high_prio; bool high_prio;
spinlock_t lock; spinlock_t lock;
struct list_head head; struct list_head head;
struct tasklet_struct bh; struct work_struct bh;
struct usb_host_endpoint *completing_ep; struct usb_host_endpoint *completing_ep;
}; };