This is a note to let you know that I've just added the patch titled
usb: gadget: Fix spinlock lockup on usb_function_deactivate
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-linus 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 hopefully also be merged in Linus's tree for the next -rc kernel release.
If you have any questions about this process, please let me know.
From 5cc35c224a80aa5a5a539510ef049faf0d6ed181 Mon Sep 17 00:00:00 2001
From: Sriharsha Allenki sallenki@codeaurora.org Date: Wed, 2 Dec 2020 18:32:20 +0530 Subject: usb: gadget: Fix spinlock lockup on usb_function_deactivate
There is a spinlock lockup as part of composite_disconnect when it tries to acquire cdev->lock as part of usb_gadget_deactivate. This is because the usb_gadget_deactivate is called from usb_function_deactivate with the same spinlock held.
This would result in the below call stack and leads to stall.
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: rcu: 3-...0: (1 GPs behind) idle=162/1/0x4000000000000000 softirq=10819/10819 fqs=2356 (detected by 2, t=5252 jiffies, g=20129, q=3770) Task dump for CPU 3: task:uvc-gadget_wlhe state:R running task stack: 0 pid: 674 ppid: 636 flags:0x00000202 Call trace: __switch_to+0xc0/0x170 _raw_spin_lock_irqsave+0x84/0xb0 composite_disconnect+0x28/0x78 configfs_composite_disconnect+0x68/0x70 usb_gadget_disconnect+0x10c/0x128 usb_gadget_deactivate+0xd4/0x108 usb_function_deactivate+0x6c/0x80 uvc_function_disconnect+0x20/0x58 uvc_v4l2_release+0x30/0x88 v4l2_release+0xbc/0xf0 __fput+0x7c/0x230 ____fput+0x14/0x20 task_work_run+0x88/0x140 do_notify_resume+0x240/0x6f0 work_pending+0x8/0x200
Fix this by doing an unlock on cdev->lock before the usb_gadget_deactivate call from usb_function_deactivate.
The same lockup can happen in the usb_gadget_activate path. Fix that path as well.
Reported-by: Peter Chen peter.chen@nxp.com Link: https://lore.kernel.org/linux-usb/20201102094936.GA29581@b29397-desktop/ Tested-by: Peter Chen peter.chen@nxp.com Signed-off-by: Sriharsha Allenki sallenki@codeaurora.org Cc: stable stable@vger.kernel.org Link: https://lore.kernel.org/r/20201202130220.24926-1-sallenki@codeaurora.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/usb/gadget/composite.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/drivers/usb/gadget/composite.c b/drivers/usb/gadget/composite.c index c6d455f2bb92..1a556a628971 100644 --- a/drivers/usb/gadget/composite.c +++ b/drivers/usb/gadget/composite.c @@ -392,8 +392,11 @@ int usb_function_deactivate(struct usb_function *function)
spin_lock_irqsave(&cdev->lock, flags);
- if (cdev->deactivations == 0) + if (cdev->deactivations == 0) { + spin_unlock_irqrestore(&cdev->lock, flags); status = usb_gadget_deactivate(cdev->gadget); + spin_lock_irqsave(&cdev->lock, flags); + } if (status == 0) cdev->deactivations++;
@@ -424,8 +427,11 @@ int usb_function_activate(struct usb_function *function) status = -EINVAL; else { cdev->deactivations--; - if (cdev->deactivations == 0) + if (cdev->deactivations == 0) { + spin_unlock_irqrestore(&cdev->lock, flags); status = usb_gadget_activate(cdev->gadget); + spin_lock_irqsave(&cdev->lock, flags); + } }
spin_unlock_irqrestore(&cdev->lock, flags);