From a00918d0521df1c7a2ec9143142a3ea998c8526d Mon Sep 17 00:00:00 2001 From: Chris Bainbridge Date: Tue, 19 May 2015 16:30:51 +0300 Subject: usb: host: xhci: add mutex for non-thread-safe data Regression in commit 638139eb95d2 ("usb: hub: allow to process more usb hub events in parallel") The regression resulted in intermittent failure to initialise a 10-port hub (with three internal VL812 4-port hub controllers) on boot, with a failure rate of around 8%, due to multiple race conditions when accessing addr_dev and slot_id in struct xhci_hcd. This regression also exposed a problem with xhci_setup_device, which "should be protected by the usb_address0_mutex" but no longer is due to commit 6fecd4f2a58c ("USB: separate usb_address0 mutexes for each bus") With separate buses (and locks) it is no longer the case that a single lock will protect xhci_setup_device from accesses by two parallel threads processing events on the two buses. Fix this by adding a mutex to protect addr_dev and slot_id in struct xhci_hcd, and by making the assignment of slot_id atomic. Fixes multiple boot errors: [ 0.583008] xhci_hcd 0000:00:14.0: Bad Slot ID 2 [ 0.583009] xhci_hcd 0000:00:14.0: Could not allocate xHCI USB device data structures [ 0.583012] usb usb1-port3: couldn't allocate usb_device And: [ 0.637409] xhci_hcd 0000:00:14.0: Error while assigning device slot ID [ 0.637417] xhci_hcd 0000:00:14.0: Max number of devices this xHCI host supports is 32. [ 0.637421] usb usb1-port1: couldn't allocate usb_device And: [ 0.753372] xhci_hcd 0000:00:14.0: ERROR: unexpected setup context command completion code 0x0. [ 0.753373] usb 1-3: hub failed to enable device, error -22 [ 0.753400] xhci_hcd 0000:00:14.0: Error while assigning device slot ID [ 0.753402] xhci_hcd 0000:00:14.0: Max number of devices this xHCI host supports is 32. [ 0.753403] usb usb1-port3: couldn't allocate usb_device And: [ 11.018386] usb 1-3: device descriptor read/all, error -110 And: [ 5.753838] xhci_hcd 0000:00:14.0: Timeout while waiting for setup device command Tested with 200 reboots, resulting in no USB hub init related errors. Fixes: 638139eb95d2 ("usb: hub: allow to process more usb hub events in parallel") Link: https://lkml.kernel.org/g/CAP-bSRb=A0iEYobdGCLpwynS7pkxpt_9ZnwyZTPVAoy0Y=Zo3Q@mail.gmail.com Signed-off-by: Chris Bainbridge Cc: # 3.18+ [changed git commit description style for checkpatch -Mathias] Signed-off-by: Mathias Nyman Signed-off-by: Greg Kroah-Hartman --- drivers/usb/host/xhci.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'drivers/usb/host/xhci.h') diff --git a/drivers/usb/host/xhci.h b/drivers/usb/host/xhci.h index ea75e8ccd3c1..6977f8491fa7 100644 --- a/drivers/usb/host/xhci.h +++ b/drivers/usb/host/xhci.h @@ -1497,6 +1497,8 @@ struct xhci_hcd { struct list_head lpm_failed_devs; /* slot enabling and address device helpers */ + /* these are not thread safe so use mutex */ + struct mutex mutex; struct completion addr_dev; int slot_id; /* For USB 3.0 LPM enable/disable. */ -- cgit v1.2.3