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Subject[PATCH v3 6/6] usb: hub: allow to process more usb hub events in parallel
Date
It seems that only choose_devnum() was not ready to process more hub
events at the same time.

All should be fine if we take bus->usb_address0_mutex there. It will
make sure that more devnums will not be chosen for the given bus and
the related devices at the same time.

Signed-off-by: Petr Mladek <pmladek@suse.cz>
---
drivers/usb/core/hub.c | 9 ++++-----
1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index 6c1a79a50576..69f9f1c1d9c1 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -2042,7 +2042,8 @@ static void choose_devnum(struct usb_device *udev)
int devnum;
struct usb_bus *bus = udev->bus;

- /* If hub_wq ever becomes multithreaded, this will need a lock */
+ /* be safe when more hub events are proceed in parallel */
+ mutex_lock(&bus->usb_address0_mutex);
if (udev->wusb) {
devnum = udev->portnum + 1;
BUG_ON(test_bit(devnum, bus->devmap.devicemap));
@@ -2060,6 +2061,7 @@ static void choose_devnum(struct usb_device *udev)
set_bit(devnum, bus->devmap.devicemap);
udev->devnum = devnum;
}
+ mutex_unlock(&bus->usb_address0_mutex);
}

static void release_devnum(struct usb_device *udev)
@@ -5162,11 +5164,8 @@ int usb_hub_init(void)
* USB-PERSIST port handover. Otherwise it might see that a full-speed
* device was gone before the EHCI controller had handed its port
* over to the companion full-speed controller.
- *
- * Also we use ordered workqueue because the code is not ready
- * for parallel execution of hub events, see choose_devnum().
*/
- hub_wq = alloc_ordered_workqueue("usb_hub_wq", WQ_FREEZABLE);
+ hub_wq = alloc_workqueue("usb_hub_wq", WQ_FREEZABLE, 0);
if (hub_wq)
return 0;

--
1.8.4


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