From: Duoming Zhou <duoming@zju.edu.cn>
Date: Sun, 17 Apr 2022 12:03:05 +0000 (+0800)
Subject: drivers: usb: host: Fix deadlock in oxu_bus_suspend()
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=d888753872190abd18f68a7d77b9c7c367f0a7ab;p=linux.git

drivers: usb: host: Fix deadlock in oxu_bus_suspend()

[ 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>
---

diff --git a/drivers/usb/host/oxu210hp-hcd.c b/drivers/usb/host/oxu210hp-hcd.c
index 4300326b3730d..6be6c5878d08b 100644
--- a/drivers/usb/host/oxu210hp-hcd.c
+++ b/drivers/usb/host/oxu210hp-hcd.c
@@ -3909,8 +3909,10 @@ 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;