2022-11-28 06:56:18

by Duoming Zhou

Subject: [PATCH] usb: mtu3: fix sleep-in-atomic-context bug caused by usleep_range()

The function zero_autoresume() is a timer handler that runs in
atomic context. It is used to wake up the host connected to the
gadget. when used by usb mtu3, the zero_autoresume() calls
usleep_range() that can sleep. As a result, the sleep-in-atomic-
context bug will happen. The process is shown below.

(atomic context)
zero_autoresume()
usb_gadget_wakeup()
mtu3_gadget_wakeup()
usleep_range() //sleep

This patch changes usleep_range(10000, 11000) to mdelay(10)
in order to mitigate the bug.

Fixes: df2069acb005 ("usb: Add MediaTek USB3 DRD driver")
Signed-off-by: Duoming Zhou <[email protected]>
---
drivers/usb/mtu3/mtu3_gadget.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/mtu3/mtu3_gadget.c b/drivers/usb/mtu3/mtu3_gadget.c
index 80236e7b089..e366c4a97d7 100644
--- a/drivers/usb/mtu3/mtu3_gadget.c
+++ b/drivers/usb/mtu3/mtu3_gadget.c
@@ -468,7 +468,7 @@ static int mtu3_gadget_wakeup(struct usb_gadget *gadget)
} else {
mtu3_setbits(mtu->mac_base, U3D_POWER_MANAGEMENT, RESUME);
spin_unlock_irqrestore(&mtu->lock, flags);
- usleep_range(10000, 11000);
+ mdelay(10);
spin_lock_irqsave(&mtu->lock, flags);
mtu3_clrbits(mtu->mac_base, U3D_POWER_MANAGEMENT, RESUME);
}
--
2.17.1

2022-12-08 15:57:50

by Greg Kroah-Hartman

Subject: Re: [PATCH] usb: mtu3: fix sleep-in-atomic-context bug caused by usleep_range()

On Mon, Nov 28, 2022 at 02:32:07PM +0800, Duoming Zhou wrote:
> The function zero_autoresume() is a timer handler that runs in
> atomic context. It is used to wake up the host connected to the
> gadget. when used by usb mtu3, the zero_autoresume() calls
> usleep_range() that can sleep. As a result, the sleep-in-atomic-
> context bug will happen. The process is shown below.
>
> (atomic context)
> zero_autoresume()
> usb_gadget_wakeup()
> mtu3_gadget_wakeup()
> usleep_range() //sleep
>
> This patch changes usleep_range(10000, 11000) to mdelay(10)
> in order to mitigate the bug.
>
> Fixes: df2069acb005 ("usb: Add MediaTek USB3 DRD driver")
> Signed-off-by: Duoming Zhou <[email protected]>
> ---
> drivers/usb/mtu3/mtu3_gadget.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/usb/mtu3/mtu3_gadget.c b/drivers/usb/mtu3/mtu3_gadget.c
> index 80236e7b089..e366c4a97d7 100644
> --- a/drivers/usb/mtu3/mtu3_gadget.c
> +++ b/drivers/usb/mtu3/mtu3_gadget.c
> @@ -468,7 +468,7 @@ static int mtu3_gadget_wakeup(struct usb_gadget *gadget)
> } else {
> mtu3_setbits(mtu->mac_base, U3D_POWER_MANAGEMENT, RESUME);
> spin_unlock_irqrestore(&mtu->lock, flags);
> - usleep_range(10000, 11000);
> + mdelay(10);
> spin_lock_irqsave(&mtu->lock, flags);
> mtu3_clrbits(mtu->mac_base, U3D_POWER_MANAGEMENT, RESUME);
> }
> --
> 2.17.1
>

Have you tested this on real hardware? How come the original code does
not trigger any run-time warnings? Does your change solve the runtime
issue?

thanks,

greg k-h