This is a note to let you know that I've just added the patch titled usb: core: hub: hub_port_init lock controller instead of bus to my usb git tree which can be found at git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git in the usb-testing branch. The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.) The patch will be merged to the usb-next branch sometime soon, after it passes testing, and the merge window is open. If you have any questions about this process, please let me know. >From feb26ac31a2a5cb88d86680d9a94916a6343e9e6 Mon Sep 17 00:00:00 2001 From: Chris Bainbridge <chris.bainbridge@xxxxxxxxx> Date: Mon, 25 Apr 2016 13:48:38 +0100 Subject: usb: core: hub: hub_port_init lock controller instead of bus The XHCI controller presents two USB buses to the system - one for USB2 and one for USB3. The hub init code (hub_port_init) is reentrant but only locks one bus per thread, leading to a race condition failure when two threads attempt to simultaneously initialise a USB2 and USB3 device: [ 8.034843] xhci_hcd 0000:00:14.0: Timeout while waiting for setup device command [ 13.183701] usb 3-3: device descriptor read/all, error -110 On a test system this failure occurred on 6% of all boots. The call traces at the point of failure are: Call Trace: [<ffffffff81b9bab7>] schedule+0x37/0x90 [<ffffffff817da7cd>] usb_kill_urb+0x8d/0xd0 [<ffffffff8111e5e0>] ? wake_up_atomic_t+0x30/0x30 [<ffffffff817dafbe>] usb_start_wait_urb+0xbe/0x150 [<ffffffff817db10c>] usb_control_msg+0xbc/0xf0 [<ffffffff817d07de>] hub_port_init+0x51e/0xb70 [<ffffffff817d4697>] hub_event+0x817/0x1570 [<ffffffff810f3e6f>] process_one_work+0x1ff/0x620 [<ffffffff810f3dcf>] ? process_one_work+0x15f/0x620 [<ffffffff810f4684>] worker_thread+0x64/0x4b0 [<ffffffff810f4620>] ? rescuer_thread+0x390/0x390 [<ffffffff810fa7f5>] kthread+0x105/0x120 [<ffffffff810fa6f0>] ? kthread_create_on_node+0x200/0x200 [<ffffffff81ba183f>] ret_from_fork+0x3f/0x70 [<ffffffff810fa6f0>] ? kthread_create_on_node+0x200/0x200 Call Trace: [<ffffffff817fd36d>] xhci_setup_device+0x53d/0xa40 [<ffffffff817fd87e>] xhci_address_device+0xe/0x10 [<ffffffff817d047f>] hub_port_init+0x1bf/0xb70 [<ffffffff811247ed>] ? trace_hardirqs_on+0xd/0x10 [<ffffffff817d4697>] hub_event+0x817/0x1570 [<ffffffff810f3e6f>] process_one_work+0x1ff/0x620 [<ffffffff810f3dcf>] ? process_one_work+0x15f/0x620 [<ffffffff810f4684>] worker_thread+0x64/0x4b0 [<ffffffff810f4620>] ? rescuer_thread+0x390/0x390 [<ffffffff810fa7f5>] kthread+0x105/0x120 [<ffffffff810fa6f0>] ? kthread_create_on_node+0x200/0x200 [<ffffffff81ba183f>] ret_from_fork+0x3f/0x70 [<ffffffff810fa6f0>] ? kthread_create_on_node+0x200/0x200 Which results from the two call chains: hub_port_init usb_get_device_descriptor usb_get_descriptor usb_control_msg usb_internal_control_msg usb_start_wait_urb usb_submit_urb / wait_for_completion_timeout / usb_kill_urb hub_port_init hub_set_address xhci_address_device xhci_setup_device Mathias Nyman explains the current behaviour violates the XHCI spec: hub_port_reset() will end up moving the corresponding xhci device slot to default state. As hub_port_reset() is called several times in hub_port_init() it sounds reasonable that we could end up with two threads having their xhci device slots in default state at the same time, which according to xhci 4.5.3 specs still is a big no no: "Note: Software shall not transition more than one Device Slot to the Default State at a time" So both threads fail at their next task after this. One fails to read the descriptor, and the other fails addressing the device. Fix this in hub_port_init by locking the USB controller (instead of an individual bus) to prevent simultaneous initialisation of both buses. Fixes: 638139eb95d2 ("usb: hub: allow to process more usb hub events in parallel") Link: https://lkml.org/lkml/2016/2/8/312 Link: https://lkml.org/lkml/2016/2/4/748 Signed-off-by: Chris Bainbridge <chris.bainbridge@xxxxxxxxx> Cc: stable <stable@xxxxxxxxxxxxxxx> Acked-by: Mathias Nyman <mathias.nyman@xxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/usb/core/hcd.c | 15 +++++++++++++-- drivers/usb/core/hub.c | 8 ++++---- include/linux/usb.h | 3 +-- include/linux/usb/hcd.h | 1 + 4 files changed, 19 insertions(+), 8 deletions(-) diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c index 2ca2cef7f681..980fc5774151 100644 --- a/drivers/usb/core/hcd.c +++ b/drivers/usb/core/hcd.c @@ -994,7 +994,7 @@ static void usb_bus_init (struct usb_bus *bus) bus->bandwidth_allocated = 0; bus->bandwidth_int_reqs = 0; bus->bandwidth_isoc_reqs = 0; - mutex_init(&bus->usb_address0_mutex); + mutex_init(&bus->devnum_next_mutex); } /*-------------------------------------------------------------------------*/ @@ -2521,6 +2521,14 @@ struct usb_hcd *usb_create_shared_hcd(const struct hc_driver *driver, return NULL; } if (primary_hcd == NULL) { + hcd->address0_mutex = kmalloc(sizeof(*hcd->address0_mutex), + GFP_KERNEL); + if (!hcd->address0_mutex) { + kfree(hcd); + dev_dbg(dev, "hcd address0 mutex alloc failed\n"); + return NULL; + } + mutex_init(hcd->address0_mutex); hcd->bandwidth_mutex = kmalloc(sizeof(*hcd->bandwidth_mutex), GFP_KERNEL); if (!hcd->bandwidth_mutex) { @@ -2532,6 +2540,7 @@ struct usb_hcd *usb_create_shared_hcd(const struct hc_driver *driver, dev_set_drvdata(dev, hcd); } else { mutex_lock(&usb_port_peer_mutex); + hcd->address0_mutex = primary_hcd->address0_mutex; hcd->bandwidth_mutex = primary_hcd->bandwidth_mutex; hcd->primary_hcd = primary_hcd; primary_hcd->primary_hcd = primary_hcd; @@ -2598,8 +2607,10 @@ static void hcd_release(struct kref *kref) struct usb_hcd *hcd = container_of (kref, struct usb_hcd, kref); mutex_lock(&usb_port_peer_mutex); - if (usb_hcd_is_primary_hcd(hcd)) + if (usb_hcd_is_primary_hcd(hcd)) { + kfree(hcd->address0_mutex); kfree(hcd->bandwidth_mutex); + } if (hcd->shared_hcd) { struct usb_hcd *peer = hcd->shared_hcd; diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c index c2270d8fac12..bee13517676f 100644 --- a/drivers/usb/core/hub.c +++ b/drivers/usb/core/hub.c @@ -2082,7 +2082,7 @@ static void choose_devnum(struct usb_device *udev) struct usb_bus *bus = udev->bus; /* be safe when more hub events are proceed in parallel */ - mutex_lock(&bus->usb_address0_mutex); + mutex_lock(&bus->devnum_next_mutex); if (udev->wusb) { devnum = udev->portnum + 1; BUG_ON(test_bit(devnum, bus->devmap.devicemap)); @@ -2100,7 +2100,7 @@ static void choose_devnum(struct usb_device *udev) set_bit(devnum, bus->devmap.devicemap); udev->devnum = devnum; } - mutex_unlock(&bus->usb_address0_mutex); + mutex_unlock(&bus->devnum_next_mutex); } static void release_devnum(struct usb_device *udev) @@ -4366,7 +4366,7 @@ hub_port_init(struct usb_hub *hub, struct usb_device *udev, int port1, if (oldspeed == USB_SPEED_LOW) delay = HUB_LONG_RESET_TIME; - mutex_lock(&hdev->bus->usb_address0_mutex); + mutex_lock(hcd->address0_mutex); /* Reset the device; full speed may morph to high speed */ /* FIXME a USB 2.0 device may morph into SuperSpeed on reset. */ @@ -4652,7 +4652,7 @@ fail: hub_port_disable(hub, port1, 0); update_devnum(udev, devnum); /* for disconnect processing */ } - mutex_unlock(&hdev->bus->usb_address0_mutex); + mutex_unlock(hcd->address0_mutex); return retval; } diff --git a/include/linux/usb.h b/include/linux/usb.h index 7824f4557d50..01b6c61cf9bb 100644 --- a/include/linux/usb.h +++ b/include/linux/usb.h @@ -374,13 +374,12 @@ struct usb_bus { int devnum_next; /* Next open device number in * round-robin allocation */ + struct mutex devnum_next_mutex; /* devnum_next mutex */ struct usb_devmap devmap; /* device address allocation map */ struct usb_device *root_hub; /* Root hub */ struct usb_bus *hs_companion; /* Companion EHCI bus, if any */ - struct mutex usb_address0_mutex; /* unaddressed device mutex */ - int bandwidth_allocated; /* on this bus: how much of the time * reserved for periodic (intr/iso) * requests is used, on average? diff --git a/include/linux/usb/hcd.h b/include/linux/usb/hcd.h index b98f831dcda3..66fc13705ab7 100644 --- a/include/linux/usb/hcd.h +++ b/include/linux/usb/hcd.h @@ -181,6 +181,7 @@ struct usb_hcd { * bandwidth_mutex should be dropped after a successful control message * to the device, or resetting the bandwidth after a failed attempt. */ + struct mutex *address0_mutex; struct mutex *bandwidth_mutex; struct usb_hcd *shared_hcd; struct usb_hcd *primary_hcd; -- 2.8.0 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html