| From a12282419082667061b6f8260b950578634cc00e Mon Sep 17 00:00:00 2001 |
| From: Sasha Levin <sashal@kernel.org> |
| Date: Sun, 17 Apr 2022 20:03:05 +0800 |
| Subject: drivers: usb: host: Fix deadlock in oxu_bus_suspend() |
| |
| From: Duoming Zhou <duoming@zju.edu.cn> |
| |
| [ Upstream commit 4d378f2ae58138d4c55684e1d274e7dd94aa6524 ] |
| |
| There is a deadlock in oxu_bus_suspend(), which is shown below: |
| |
| (Thread 1) | (Thread 2) |
| | timer_action() |
| oxu_bus_suspend() | mod_timer() |
| spin_lock_irq() //(1) | (wait a time) |
| ... | oxu_watchdog() |
| del_timer_sync() | spin_lock_irq() //(2) |
| (wait timer to stop) | ... |
| |
| We hold oxu->lock in position (1) of thread 1, and use |
| del_timer_sync() to wait timer to stop, but timer handler |
| also need oxu->lock in position (2) of thread 2. As a result, |
| oxu_bus_suspend() will block forever. |
| |
| This patch extracts del_timer_sync() from the protection of |
| spin_lock_irq(), which could let timer handler to obtain |
| the needed lock. |
| |
| Signed-off-by: Duoming Zhou <duoming@zju.edu.cn> |
| Link: https://lore.kernel.org/r/20220417120305.64577-1-duoming@zju.edu.cn |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| Signed-off-by: Sasha Levin <sashal@kernel.org> |
| --- |
| drivers/usb/host/oxu210hp-hcd.c | 2 ++ |
| 1 file changed, 2 insertions(+) |
| |
| diff --git a/drivers/usb/host/oxu210hp-hcd.c b/drivers/usb/host/oxu210hp-hcd.c |
| index 2f48da0c0bb3..af5248f62c59 100644 |
| --- a/drivers/usb/host/oxu210hp-hcd.c |
| +++ b/drivers/usb/host/oxu210hp-hcd.c |
| @@ -3491,8 +3491,10 @@ static int oxu_bus_suspend(struct usb_hcd *hcd) |
| } |
| } |
| |
| + spin_unlock_irq(&oxu->lock); |
| /* turn off now-idle HC */ |
| del_timer_sync(&oxu->watchdog); |
| + spin_lock_irq(&oxu->lock); |
| ehci_halt(oxu); |
| hcd->state = HC_STATE_SUSPENDED; |
| |
| -- |
| 2.35.1 |
| |
